AlllOS 183871

REFERENCE Pubiications

NBSIR 84-2875

NBS

PHYSICAL

MEASUREMENT

SERVICES

STATUS REPORT

May 1984

U.S. Department of Commerce

National Bureau of Standards

—QC

130

. U5G

84-2375

1984

NBSIR 84-2875

NBS

PHYSICAL

MEASUREMENT

SERVICES

STATUS REPORT

Office of

Measurement Services

National Bureau of Standards

Washington, D.C. 20234

NATIONAL BUREAU OF STANDARDS

LIBRARY QU

Editors:

Lottie T. McClendon

R. Keith Kirby

U.S. Department of Commerce

National Bureau of Standards

TABLE OF CONTENTS

Page

FOREWORD i i i

CALIBRATION SERVICE (CLASSIFICATION NO.)

Mass (1.1) 1

Length Measurements (1.3) 6

Length and Diameter Dimensional Metrology (1.4) 10

Complex Standards of Length and Diameter (1.5) 13

Flatness, Straightness, and Roundness (1.6) 15

Angular (1.7) 16

Surface Texture (1.8) 18

Image Optics and Photography (1.9) 20

Acoustic Measurements (2.1) 21

Vibration Measurements (2.2) 27

Humidity Measurements (2.3) . . 30

Calibration of Force Transducers and Force Measurement

Systems (2.5) 32

Fluid Quantity and Flow Rate Meters (2.7) 34

Aerodynamics (2.9) 37

Resistance Measurements (3.1) 39

Precision Apparatus (3.2) 42

Impedance Measurements (3.3) 43

Voltage Measurements (3.4) 45

Electrical Instruments (3.5) 47

DC-AC Voltage, Current, and Power Measurements (3.6) .... 49

Wattmeter and AC Voltage Measurements (3.8) 53

Data Converter Measurements (3.9) 54

Attenuation (4.1) 57

Field and Antenna Measurements (4.2) 60

Impedance or Admittance (4.3) 63

Laser Power and Energy (4.4) 67

Noise Temperature Measurements (4.6) 69

Phase Shift (4.7) 71

Radio and Microwave Wave Power Measurements (4.8) 75

Voltage (4.9) 77

Time and Frequency (5.1 - 5.2) 81

Laboratory Thermometers (7.1) 85

Thermocouples and Thermocouple Materials (7.2) 87

Standard Platinum Resistance Thermometers (7.3) 90

Radiation Thermometry (7.4) 92

Radiometric Standards (7.5) 94

Near and Vacuum Ultraviolet Radiometric Standards (7.6) ... 99

Photometric Standards (7.7) 101

Spectrophotometric Standards (7.8) 103

Pressure and Vacuum Measurements (7.9) 106

1
Page

Neutron Sources and Dosimetry Standardization (8.1) 109

Radioactivity Calibrations (8.2) .... 115

X-Ray and Gamma-Ray Measuring Instruments (8.3) 119

Gamma-Ray and Beta-Particle Sources (8.4) 121

Dosimetry of High-Energy Electron Beams (8.5) 123

Dosimetry for High-Dose Applications (8.6) 124

NBS MEASUREMENT SEMINARS 127

i i
FOREWORD

An essential element of the mission of the National Bureau of

Standards (NBS), a major technical agency of the Department of Commerce,

is to provide the basis for a complete and consistent national system of

physical measurements. The Bureau accomplishes this in a variety of

ways, the calibration of instruments and devices being one of the most

familiar. This publication is intended to provide the reader with a brief summary of each of the currently available NBS Physical Measurement Services. More detailed technical and general information on each

of the services will be provided in the upcoming 1984 Edition of NBS

Special Publication 250 entitled "Calibration and Related Measurement

Services of the NBS."

Information of five types is provided for each of the NBS

services - description of service; documentation associated with the

service; training programs available on that service; future directions;

and contact person at NBS. To assist the reader in locating particular

services by number, the previously assigned NBS classification number

for each measurement service is listed along with the title of the

service (e.g. , Mass (1.1), Acoustic Measurements (2.1), etc.). A list

of NBS measurement seminars to be held during 1984 is also included in

this publication.

Generally speaking, NBS 1 services are provided for special calibrations which are not readily available elsewhere and for calibrations

which require direct reference to national standards. Private metrology

laboratories offering services to the general public can be found

throughout the United States. It is not uncommon to find laboratories

which, in certain areas of specialty, are capable of making measurements

on a par with those made at NBS. Accordingly, employing the services of

a reputable private calibration laboratory may be an adequate and cost

effective solution to many commonly encountered measurement problems.

Two national organizations that can provide information regarding names

and addresses of private calibration and test laboratories are:

National Conference of Standards Laboratories

c/o NCSL Secretariat

National Bureau of Standards

Boulder, CO 80303

(303) 497-3787

(Note: NCSL Directories are also available from the Office of

Measurement Services, NBS-Gaithersburg.

American Council of Independent Laboratories, Inc.

1725 K Street, NW

Suite 301

Washington, DC 20006

(202) 887-5872
Additional information regarding NBS measurement services can be

obtained from:

George Uriano, Director

Office of Measurement Services

National Bureau of Standards

Bldg. 220, Rm. A363

Washington, DC 20234

(301) 921-2606

ACKNOWLEDGMENT

This report represents the joint efforts of many who have contributed

to this compilation. The editors want to express their appreciation to

all who have made it possible to produce this document in a short few

months
MASS (1.1)

Description of Services

The National Bureau of Standards (NBS) maintains the national

standards for mass in the form of the prototype kilograms (K4 and K20)

and provides services to support the parts of the national measurement

system that rely directly or indirectly on mass measurements. These

services include the calibration of suitable weight sets and the

establishment of measurement assurance programs that will assist users

in establishing and maintaining a state of statistical control for the

measurements, the determination of the offset of the process from the

national system, and assisting in the determination of the uncertainty

of measurements made by the user's process.

The NBS calibration of reference standards of mass provides

extensions of the mass unit embodied in the NBS standards of mass. A

calibration consists of establishing a mass value and the appropriate

uncertainty for that value for each weight which has been designated to

be a reference standard. It is desirable, but not necessary, that a weight meet the adjustment tolerances established for Classes A, B, M, or S-l prior to submission. Weights are available from manufacturers,

many of whom can furnish directly documentation suitable for meeting

quality assurance contracts and requirements.

For periodic recalibrations of reference mass standards, the user

need measure only differences between weights or groups of weights

within a set and compare them with computed differences. As long as the

agreement is within allowable limits, the values can be considered

constant within the precision of the comparison process. Mass standards

which are submitted to NBS for recalibration frequently are tested in

this manner. If these tests indicate that no significant changes have

occurred, a continuation report so stating and referring to the previous

NBS Report of Calibration will be issued.

NBS calibrates individual weights or sets in the range of 30 kg to

1 mg or 50 lb to 1 plb in decimal subdivisions. If the weights are designated as reference standards, they must be of design, material, and

surface finish comparable to present Classes A, B, M, S, or S-l. NBS

also calibrates large mass standards (60 to 60,000 lbs) if the design,

material, and surface finish are compatible with the intended usage.

For these large mass standards an adjustment with reference to a nominal

or desired value can be included as a part of the calibration procedure.

The values of true mass (and an apparent mass correction) included

in the report will be determined by using computed volumes based on the

manufacturer's statement of density of the material, on the density

computed from measured volumes, or, in the absence of this information,

on estimated density values. The apparent mass corrections are computed

for 20 °C with reference to Normal Brass (density 8.4 g/cm3 at 0 °C,

volume coefficient of expansion 0.000054/°C) and to stainless steel

(density 8.0 g/cm3 at 0 °C, volume coefficient of expansion 0.000045/°C)

in an ideal air density of 1.2 mg/cm3

. Apparent mass corrections to any

other basis can be furnished if requested. Typical uncertainties range

1
from 50 parts per billion at 1 kilogram up to 500 parts per million at one milligram and 1 part per million for weights from 2 kilograms to 30

kilograms.

NBS will calibrate metal volumetric reference standards which have

volumes in the range 1 gill (4 fluid ounces) to 100 gallons and glass

volumetric apparatus which have volumes in the range 1 milliliter to 1

gallon if suitable service is not available otherwise. Acceptance of an item for calibration or test is based on discussion with the user to

determine that the item and its intended use meet requirements for a volumetric reference standard.

NBS will accept requests for density determinations of liquids if

the need is critical, as in the support of standard sample programs or scientific studies. Limitations on the mass, physical dimensions, or volume of the sample are available on request. At NBS, liquid densities

usually are determined by gravimetric (that is, weighing) methods.

Other methods are available depending on the requirements. Reference

hydrometers (0.62 - 3.0 g/cm3 range) are normally used as laboratory

standards for transfer of measurement capabil ity/traceabil ity to other

hydrometers.

Documentation

Measurement Philosophy of the Pilot Program for Mass Calibration, P. E. Pontius, Natl. Bur. Stand. (U.S.), Tech. Note 288, 41 pages (May 1966).

Introduction to Intercomparison Methods in Mass Measurement, H. E. Aimer, Natl. Bur. Stand. (U.S.), Report 9487, 15 pages (Feb. 1967).

Realistic Uncertainties and the Mass Measurement Process, P. E. Pontius

and J. M. Cameron, Natl. Bur. Stand. (U.S.), Monogr. 103, 18 pages (Aug.

1967).

Method of Calibrating Weights for Piston Gages, H. E. Aimer, Natl. Bur.

Stand. (U.S.), Tech. Note 577, 49 pages (May 1971).

On Uncertainty in Mass Measurement, J. R. Donaldson, Natl. Bur. Stand.

(U.S.), NBSIR 73-151, 10 pages (Mar. 1973).

Weight Cleaning Procedures, H. E. Aimer, Natl. Bur. Stand. (U.S.), NBSIR

74-443 , 7 pages (Nov. 1973).

Mass and Mass Values, P. E. Pontius, Natl. Bur. Stand. (U.S.), Monogr.

133, 39 pages (Jan. 1974).

Notes on the Fundamentals of Measurement and Measurement as a Production

Process, P. E. Pontius, Natl. Bur. Stand. (U.S.), NBSIR 74-545, 65 pages

(Sept. 1974).

The Use of the Method of Least Squares in Calibration, J. M. Cameron,

Natl. Bur. Stand. (U.S.), NBSIR 74-587, 30 pages (1974).

Surveillance Test Procedures, H. W. Aimer, Natl. Bur. Stand. (U.S.),

NBSIR 76-999, 73 pages (Feb. 1976).

2
Designs for the Calibration of Standards of Mass, J. M. Cameron, M. C.

Croarkin, and R. C. Raybold, Natl. Bur. Stand. (U.S.), Tech. Note 952,

64 pages (June 1977).

The Air Density Equation and the Transfer of the Mass Unit, F. E. Jones,

Natl. Bur. Stand. (U.S.), NBSIR 77-1278, 30 pages (July 1977).

Measurement Assurance, J. ML Cameron, Natl. Bur. Stand. (U.S.), NBSIR

77-1240, 13 pages (1977).

The National Measurement System for Mass, Volume, and Density, P. E. Pontius, J. R. Whetstone, and J. A. Simpson, Natl. Bur. Stand. (U.S.),

NBSIR 75-928, 72 pages (May 1978).

Direct Determination of Air Density in a Balance Through Artifacts

Characterized in an Evacuated Weighing Chamber, W. F. Koch, R. S. Davis,

and V. E. Bower, J. Res. Natl. Bur. Stand. (U.S.), 83, No. 5, 407-413

(Sept. -Oct. 1978).

The Air Density Equation and the Transfer of the Mass Unit, F. E. Jones,

J. Res. Natl. Bur. Stand. (U.S.), 83, No. 5, 419-428 (Sept. -Oct. 1978).

Precision Laboratory Standards of Mass and Laboratory Weights. A

reprint of NBS Circular 547, Section 1, Lahof and Macurdy, August 1954,

Natl. Bur. Stand. (U.S.), NBSIR 78-1476, 21 pages (Oct. 1978).

National Bureau of Standards Mass Calibration Computer Software, R. N. Varner and R. C. Raybold, Natl. Bur. Stand. (U.S.), Tech. Note 1127, 158

pages (July 1980).

Quick and Accurate Density Determination of Laboratory Weights, R. M. Schoonover and R. S. Davis, Proceedings of the 8th Conference of IMEKO

Tech. Comm. TC3, Measurement of Force and Mass, Weighing Technology,

Krakow, Poland, Sept. 9-11, 1980.

Air Buoyancy Correction in High-Accuracy Weighing on Analytical

Balances, R. M. Schoonover and F. E. Jones, Anal. Chem. , 53, No. 6,

900-902 (May 1981).

Procedures for the Calibration of Volumetric Test Measures, J. F. Houser, Natl. Bur. Stand. (U.S.), NBSIR 73-287, 24 pages (Aug. 1973).

Order from NTIS as COM 73-11928.

Calibration of Small Volumetric Laboratory Glassware, J. Lembeck, Natl.

Bur. Stand. (U.S.), NBSIR 74-461, 34 pages (Oct. 1974). Order from NTIS

as PB246623.

The Equivalence of Gravimetric and Volumetric Test Measure Calibration,

R. M. Schoonover, Natl. Bur. Stand. (U.S.), NBSIR 74-454, 16 pages (Feb.

1974). Order from NTIS as COM 74-10988.

A Density Scale Based on Solid Objects, H. A. Bowman, R. M. Schoonover,

and C. L. Carroll, J. Res. Natl. Bur. Stand. (U.S.), 78A, No. 1, 13-40,

(Jan. -Feb. 1974).

3
Training Programs

None.

Future Directions

Transfer standards used for volumetric test measures (1 to 100 U.S.

gallons) will be redetermined using gravimetric techniques.

Measurements on the five gallon slicker-plate vessel have been

completed. The current results are in agreement with the previous

values at the 5 part in 10 s level. The 30, 50, and 100 gallon test

measures will be determined gravimetrical ly to complete the surveillance

measurements. Publication of the new results and comparison with the

previous values will be combined in an NBSIR which will provide the most

recent documentation of the assessment of the measurement uncertainties

for this calibration service.

Efforts are underway to tie the measurements made in the calibration

of hydrometers or other liquid density measurement devices to the NBS

Single Crystal Silicon density standards, which will provide the tie to

the basic units of mass and length.

Relatively recent technology provides a means for liquid density

determination which provides an alternative to hydrometry. This technique utilizes an electromechanical resonance technique to compare the

density of liquids of unknown density with that of two calibration

fluids of known density. Calibration of this comparative device with

liquids spanning the density range of interest allows the rapid and

accurate measurement of the densities of other liquids. The comparative

precision of the instrument approaches one part per million under the

best of conditions, which is much better than that routinely required in

hydrometry. Given an appropriately selected set of calibration fluids,

the density range of normal liquids is easily covered. Therefore,

efforts are focused on the development of a set of liquids with densities

covering the range 0.7 to 2.0 g/cm3 with the intent of offering this set

as a standard reference material.

The modification of a hydrostatic weighing technique which allows

the assignment of density values to solids which are directly tied to

the NBS Single Crystal Silicon density standards will enable NBS to

assign density values for a variety of liquids. The liquids involved in

these modification experiments will become the liquid density SRM and

will span the density range of 0.7 to near 2.0 g/cm3 . In addition to a density value, each will be assigned a thermal expansion coefficient

val ue.

Once the liquid density SRM is available and by using distilled

water, an alternative is available for liquid density measurement using

the electromechanical density comparator discussed previously. This

alternative also provides a method to calibrate hydrometers using the

density comparator and the SRM to determine the density of the bath used

to observe the hydrometer indication, thereby determining the difference

between the actual and indicated density values. This difference is the

correction for which hydrometers are normally calibrated.
NBS is re-evaluating its activities in the mass area and the

results from the evaluation will be reported later.

Contact Person at NBS

Jerry Keller (Mass)

Mechanical Production Metrology Division

301 - 921-3118

James Whetstone (Density and Volume)

Chemical Process Metrology Division

301- 921-3681

5
LENGTH MEASUREMENTS (1.3)

Description of Services

These services include the measurement of gage blocks, line

standards (40 inches or less), and surveying tapes and leveling rods.

Measurement of the length of gage blocks is determined by either

comparison to NBS master gage blocks or by direct interferometry.

Generally the length is transferred from the NBS master blocks by a systematized intercomparison sequence using mechanical comparators. The

intercomparison sequence and a description of the statistics for measure- ment assurance for the process are described in the references below.

Single or multiple wavelength interferometric measurements are also

available at special request.

Square or rectangular gage blocks of lengths up to 20 inches are routinely calibrated and the lengths reported in English or metric

units. For blocks longer than 20 inches the Dimensional Metrology Group

should be contacted in advance to discuss alternative measurement

techniques. A reasonable estimate for the accuracy of the calibration

is 2 microinches (0.05 micrometer) for blocks under 2 inches, and

decreasing accuracy with length to 20 microinches for the 20- inch

blocks.

There is available a Gage Block Measurement Assurance Program (MAP)

for users who wish the highest possible accuracy of transfer of the

length standard. This program has a number of variations and the cost

depends on the variation selected. The program is described in NBS

Monograph 163, "Measurement Assurance for Gage Blocks."

Line standards of 1 meter or less are measured on an instrument

called a line scale interferometer. It is used to measure the distance

between suitable lines on a flat surface. The instrument employs a fixed photoelectric microscope to determine the position of the scale

lines, a linearly mobile carriage in the focal plane of the microscope

to carry the scales, two interferometers (one commercial unit and one NBS-made Michel son) that can be used separately or in tandem to measure carriage displacement, and a temperature-controlled housing enclosing

the whole apparatus.

The maximum length of line standards that can be measured is 1

meter, and the maximum width of any part of the piece being calibrated

cannot exceed 150 millimeters. The accuracy of the calibration depends

significantly on the shape and optical properties of the line, the

background, and the geometric flatness of the artifact being calibrated.

If the lines have straight edges, are 2 to 10 micrometers wide, there is

good contrast between the line and the background, and the reference

surface of the artifact is flat, then the accuracy of the calibration

will be near optimum. Uncertainties as low as 0.006 micrometer have

been achieved on short intervals and on 1-meter lengths uncertainties of

0.1 micrometer can be achieved. Current overall system accuracy is

limited by imprecise knowledge of the refractive index of air to normal

operating conditions.

6
The calibration of surveying tapes (and oil gaging tapes) is

carried out in the Long Length Calibration Laboratory. This laboratory

houses two permanent working standards; a laser interferometer and a 50-meter (200-foot) stainless steel bench. Measurements are performed

for the most part using the laser system which is referenced against a cube-corner retroref lector attached to a microscope which is used

manually for line location. The laboratory is maintained at 20 °C, but

an independent environmental control system can vary the chamber temperature from 15 to 40 °C for special tests.

Normal calibration of tapes will be made with the tape under

tension and supported on a horizontal -flat surface in a laboratory

controlled to 20 °C. Unless otherwise requested, the total length and

each 15-meter or 50-foot subinterval will be measured and reported.

Each interval calibrated on a surveying tape will have computed lengths

for two (single catenary), three, four, and five equidistant points of

support. The laser standard is capable of calibrating tapes with

scribed graduations to an accuracy of 2 parts per million. Calibrations

made with respect to the stainless steel bench are normally reported to an accuracy of 10 parts per million.

Leveling rods are currently calibrated using two methods. One

method involves the comparison of the rod to a 3-meter standard at the

one, two, and three-meter intervals. A second system provides measurement at multiple intervals and automatic report generation. This system

incorporates a 7-meter one-dimensional measuring machine, a motorized

carriage, a photoelectric microscope and a helium-neon laser interferometer interfaced to a large minicomputer. Measurements can be made on virtually any type of linear scale or leveling rod with scribed,

engraved or painted graduations.

The random error of measuring high quality leveling rods is plus or minus 6 micrometers for new rods and plus or minus 12 micrometers for

used rods at the one standard deviation level. The systematic errors

are largely un-eval uated, and to account for their existence the total

error being reported by NBS at present is plus or minus 50 micrometers

for new rods. The length of intervals will be reported at 20 °C unless

otherwise requested. The report can be supplied in either written or computer- readable form.

NBS can provide measurement services for sieves—i.e., tests for

conformity to ASTM specifications—if arrangements are made in advance.

Documentation

Measurement Assurance for Gage Blocks, C. Croarkin, J. Beers, and C. Tucker, Natl. Bur. Stand. (U.S.), Monogr. 163, 75 pages (Feb. 1979).

Measurement Assurance Program--A Case Study: Length Measurements. Part

1. Long Gage Blocks (5 in to 20 in), P. E. Pontius, Natl. Bur. Stand.

(U.S.), Monogr. 149, 75 pages (Nov. 1975).

Gage Block Flatness and Parallelism Measurement, J. S. Beers and C. D. Tucker, Natl. Bur. Stand. (U.S.), NBSIR 73-239, 12 pages (Aug. 1973).

Order from NTIS as PB273962.

7
Intercomparison Procedures for Gage Blocks Using Electromechanical

Comparators, J. S. Beers and C. D. Tucker, Natl. Bur. -Stand. (U.S.),

NBSIR 76-979, 23 pages (Jan. 1976). Order from NTIS as PB248992.

A Gage Block Measurement Process Using Single Wavelength Interferometry,

J. S. Beers, Natl. Bur. Stand. (U.S.), Monogr. 152, 34 pages (Dec.

1975).

Preparations for Gage Block Comparison Measurements, C. D. Tucker, Natl.

Bur. Stand. (U.S.), NBSIR 74-523, 14 pages (July 1974). Order from NTIS

as COM 75-11126.

Contact Deformation in Gage Block Comparisons, J. S. Beers and J. E. Taylor, Natl. Bur. Stand. (U.S.), Tech. Note 962, 46 pages (May 1978).

Interferometric Measurement of Length Scales at the National Bureau of

Standards, J. S. Beers and K. B. Lee, Precision Engineering, 4, No. 4,

205-214 (Oct. 1982).

An Automatic Fringe Counting Interferometer for Use in the Calibration

of Line Scales, H. D. Cook and L. A. Marzetta, J. Res. Natl. Bur.

Stand. (U.S.), 65C, 129 (1961).

Training Programs

There are currently no training programs available in the length

metrology area because of its very highly specialized nature. The NBS

Dimensional Metrology Group is, however, open to discussions regarding

workshops and Research Associate programs for those companies interested

in learning this technology. These programs have been conducted in the

past and proved to be a very successful means of transferring this

complex technology.

Future Directions

For some years now the gage block data acquisition and report

generation has been highly automated for the mechanical intercomparisons.

This automation was done using a central minicomputer system. At this

time this older system is being modified so that the laboratory will be

automated by a stand-alone microcomputer system. Upon the completion of

this task a report will be generated and the next research thrust will

be in the direction of developing the experimental methods and acquiring

data to enhance the accuracy of interferometric measurements of gage

blocks.

The interferometric system used in measuring line standards is

currently being upgraded to provide higher accuracies and faster

calibrations. In particular it is being fitted with a new carriage

servo system based around two mi 1 1 iarc-second autocoll imators which will

be used in the servo loop to control angular motion of the carriage.

Also being added to the instrument in the next few years will be a new interferometer system which derives the laser frequency from the iodine

stabilized helium-neon laser and provides for very precise on-line

compensation for changes in air refractive index. A new document is in

8
preparation which will describe the complete measurement algorithm used

for the measurement of several common types of length scale.

The Long Length Laboratory is in the process of being partially

automated using a laboratory microcomputer interfaced to the laser

interferometer and temperature-measurement systems. Some research is

also being performed into the calibration of remote length-measuring

devices, and this calibration may soon be available on a special test

basis. A publication is planned, that will describe the whole system,

and will be issued in 1985. The calibration reports are currently

computer-generated, however, and provide the user with considerable

information regarding the calibration procedure.

Future work on leveling rods will be to undertake a thorough study

of all systematic error sources in their measurement, with overall goals

of (a) eliminating as many sources as possible, (b) reducing the overall

uncertainty of the calibrations, and (c) hardening the database on which

the error estimate rests. A report summarizing the results of this

study will be prepared.

Contact Person at NBS

Theodore Doiron

Automated Production Technology Division

301-921-2216

9
LENGTH AND DIAMETER DIMENSIONAL METROLOGY (1.4)

Description of Services

NBS provides a calibration service for the measurement of the

diameter of thread and gear wires by intercomparison to NBS Master

wires. The diameter is transferred from known Master wires using a systematized intercomparison sequence with a mechanical comparator.

All measuring wires submitted for test should be in substantially

new condition. Each wire should be appropriately bottled, and the

bottle should be labeled with an identification number. In shipping

thread wires extreme care should be taken to prevent corrosion, and all

wires should be properly greased and their bottles rigidly contained

inside an appropriate packing case.

Thread measuring wires for 60-degree and 29-degree threads are tested for compliance with the latest specifications in commercial use. Special thread measuring wires for unusual sizes and for threads finer

than 80 tpi are measured as a special test in a manner consistent with

current commercial practice. Gear measuring wires in the 1.92"/P,

1.728"/P, 1.44"/P, and 1.68"/P series are tested for compliance with the

latest specifications in commercial use and the mean diameter reported.

Accuracies are reported to a 3-sigma confidence level of 10 microinches

for English wires and 0.25 micrometer for metric wires. The NBS has a wide variety of state-of-the-art metrology equipment and can provide

other test and calibration services associated with dimensional quality

control as special tests. Listed below are some of the capabilities

available for special tests. Arrangements for these tests should be

made in advance.

(a) A three-dimensional measuring machine is available for

calibration of two- and three-dimensional ball plates, two-dimensional

grid plates, and other artifacts of complex shape. The machine has a working volume of 48 x 24 x 12 inches and can detect a length difference

of 0.013 micrometer. Reference to the international standard of length

is through interferometers. Uncertainties in the calibrations are

variable.

(b) End standards having spherical, flat, or pointed ends can be

measured. End standards up to 20 feet in length can be calibrated to

high accuracy. Lengths are reported with 2.5-lb measuring force unless

otherwise requested.

(c) Step gages having flat, parallel faces along a common center

line are calibrated as special tests.

(d) Internal and external diameter standards, such as plug and

ring gages, are accepted for measuring.

(e) Spherical diameter standards, such as balls used in precision

bearings and master balls used as transfer diameter standards, are calibrated using a laser-based mechanical comparator.

10
Documentation

On the Measurement of Thread Measuring Wires, B. N. Norden, Natl. Bur.

Stand. (U.S.), Report 10987 (Jan. 1973).

Measurement Assurance for Gage Blocks, C. Croarkin, J. Beers, and C.

Tucker, Natl. Bur. Stand. (U.S.), Monogr. 163, 75 pages (Feb. 1979).

Intercomparison Procedures for Gage Blocks Using Electromechanical

Comparators, J. S. Beers and C. D. Tucker, Natl. Bur. Stand. (U.S.),

NBSIR 76-979, 23 pages (Jan. 1976). Order from NTIS as PB248992.

Federal Standard H-28, Screw Thread Standards for Federal Services.

English and metric versions. These handbooks are available from GSA.

American National Standard B1.2, available from ANSI Headquarters, New

York, New York.

Measurements of Cylindrical Standards, R. C. Veale, Natl. Bur. Stand.

(U.S.), NBSIR 73-136 (1973).

On the Comparison of Cylinder in Contact with a Plain Surface, B. Norden, Natl. Bur. Stand. (U.S.), NBSIR 73-243 (1973).

Designs for the Calibration of Small Groups of Standards in the Presence

of Instrumental Drift, J. M. Cameron and G. E. Hieles, Natl. Bur. Stand.

(U.S.), Tech. Note 844 (Aug. 1974).

On Characterizing Measuring Machine Geometry, R. J. Hocken and B. R. Borchardt, Natl. Bur. Stand. (U.S.), NBSIR 79-1752 (1979).

Three-Dimensional Metrology, R. Hocken, J. Simpson, et al., Annals of

the CIRP, 26-1 (1977).

Unified Three-Dimensional Program - Two Useful Non-Contacting Probes, J.

A. Simpson, Natl. Bur. Stand. (U.S.), Report 10597 (1971).

Training Programs

No formal training programs are currently available. However,

special cases for training are treated on a case-by-case basis.

Future Directions

The thread wire calibration laboratory will undergo a modification

of the data acquisition procedure. The system will be switched from the

central minicomputer, which is now obsolete, to a local laboratory

microcomputer. Efforts are also being made to procure new measuring

instrumentation which will allow laser measurement of the wires and

reduce the number of Masters currently required. NBS plans to maintain

state-of-the-art measurement capability in all dimensional geometric

measurements relevant to mechanical manufacturing and quality control.

These services will be expanding in the future by the procurement of new measuring machines and the development of new measurement technology.

U
Contact Person at NBS

Robert Hocken

Automated Production Technology Division

301- 921-2577

12
COMPLEX STANDARDS OF LENGTH AND DIAMETER (1.5)

Description of Services

NBS provides calibration and certification services for API

threaded plug and ring gages, casing, tubing and line pipe plug and ring

gages as well as sucker rod gages.

NBS is the custodian of the American Petroleum Institute (API)

Grand Master rotary thread gages. These Grand Master gages are maintained and have been recalibrated in our laboratory for more than 40

years. They can be considered an international artifact since all API

Regional Master Gages throughout the world are referenced to NBS.

Foreign product manufacturers can have their Reference Master Gages

calibrated and certified by NBS or by one of the following national

standard laboratories:

National Physical Laboratory, Teddington, England

National Research Laboratory of Metrology, Tokyo, Japan

National Standards Laboratory, Chippendale, N.S.W. , Australia

Physikalisch Technische Bundesanstalt, Braunschweig, Germany

Laboratoire National d'Essais, Paris, France

Parameters measured for plug gages are:

Length of plug

Taper

Pitch diameter

Major diameter

Thread lead

Load and following thread half-angles

Depth of thread - pitch line width and radius of curvature

Parameters measured for ring gages are:

Length of ring

Taper

Thread lead

Minor diameter

Lead and following thread half-angles

Counter bore

Depth of thread

Pitch line width - radius of curvature and standoff

These calibrations are based on a three standard deviation confidence

level and are accurate to plus or minus 0.0003 inch.

Micrometer calipers, vernier calipers, plain snap gages, micrometer

screws, dial micrometers, and other similar devices are accepted for

calibration under special circumstances. Precision penetration needles

and cones are also tested for compliance to ASTM specifications.

Arrangements for services in these areas should be made in advance.

13
Documentation

Threaded plug and ring gage calibrations are currently limited to

those gages conforming to current API specifications. API Regional

Masters and Reference Master thread gages are tested as required by API

Standards 5B, 7, and 11B. These specifications and tests are well

documented in API publications available from the American Petroleum

Institute , 211 North Erbay, Suite 1700, Dallas, TX 75201. Further

documentation of the current measuring system is not required.

Training Programs

Formal training programs are not available for API gage calibration.

In the past, however, NBS has made itself available for individual

training of those technicians required by gage manufacturers for their

gage quality control. These technicians spend approximately two weeks

at NBS learning our measurement methodologies. Individual arrangements

should be made by contacting NBS.

Future Directions

A major effort in the API calibration area will focus on the

transfer of measurements made on present instrumentation to a new computer-controlled high-accuracy coordinate measuring machine. The

transfer of measurements and calibration report preparation to this

automated system are expected to be complete in late 1985.

Contact Person at NBS

Robert Hocken

Automated Production Technology Division

301-921-2577

or

Theodore Doiron

Automated Production Technology Division

301-921-2216

14
FLATNESS, STRAIGHTNESS, AND ROUNDNESS (1.6)

Description of Services

NBS provides services for optical reference planes and roundness

measurements as special tests, since such services are not performed

frequently enough to merit maintenance of a full scale calibration

laboratory. Arrangements for these services should be made in advance.

Optical reference planes (such as flats) and surface plates are calibrated optically or mechanically. Roundness measurements on parts

and gages are made and the results may be reported graphically.

Documentation

A Survey of the Stability of Optical Flats, C. P. Reeve and R. C. Veale,

Natl. Bur. Stand. (U.S.), NBSIR 73-232, 27 pages (June 1973). Order

from NTIS as PB273947.

The Calibration of an Optical Flat by Interferometric Comparison to a Master Optical Flat, C. P. Reeve, Natl. Bur. Stand. (U.S.), NBSIR

75-975, 40 pages (Dec. 1975). Order from NTIS as PB253113.

Training Programs

No formal training program is available, however, special requests

for individualized training are treated on a case-by-case basis.

Future Directions

NBS plans to maintain state-of-the-art measurement capability in

all dimensional geometric measurements relevant to mechanical

manufacturing and quality control.

Contact Person at NBS

Robert Hocken

Automated Production Technology Division

301-921-2577

or

Theodore Doiron

Automated Production Technology Division

301-921-2216

15
ANGULAR (1.7)

Description of Services

NBS provides calibration services for all standard sizes of angle

gage blocks. Blocks with angles ranging from 1 arc-second to 45 degrees

are routinely handled, however, optical squares and other standards can also be accommodated. Accuracy at the 3-sigma level is approximately

0.1 arc-second, however, this value varies with the condition of the

gaging surface on the standard. The measurement of the angle of angle

blocks is made by direct comparison to NBS Master angle blocks using a dual-autocollimator system. Current autocollimators have resolution to

0.01 arc-second and electronic readout. The blocks are enclosed in a special chamber during intercomparison to minimize air currents, and the

laboratory is maintained at 20 degrees Celsius to within plus or minus

0.1 degree. The intercomparison sequence has been systematized.

Angular standards of various types, including polygons, wedges, and

the like, are calibrated by comparison or interferometry. Precision

rotary and indexing tables, autocoll imating telescopes, and

angle-generating equipment and transducers are calibrated at specific

angular settings. These services, however, are provided as special

tests and arrangements must be made in advance by the customer.

Documentation

The Calibration of Angle Blocks by Intercomparison, C. P. Reeve, Natl.

Bur. Stand. (U.S.), NBSIR 80-1967 (1980).

Designs for the Calibration of Small Groups of Standards in the Presence

of Instrumental Drift, J. M. Cameron and G. E. Hieles, Natl. Bur. Stand.

(U.S.), Tech. Note 844 (Aug. 1974).

A Survey of the Temporal Stability of Angle Blocks, R. C. Veale and C.

P. Reeve, Natl. Bur. Stand. (U.S.), NBSIR 74-601, 22 pages (Nov. 1974).

Order from NTIS as PB273948.

The Calibration of Indexing Tables by Subdivision, C. P. Reeve, Natl.

Bur. Stand. (U.S.), NBSIR 75-750, 38 pages (July 1975). Order from NTIS

as PB249934.

Training Programs

No formal training programs in angle block calibration exist.

Requests for specialized one-on-one training will be considered on a case-by-case basis.

Future Directions

The NBS angle block calibration facility is now partially

automated. The system will be modified for direct on-line data

acquisition and report generation using a laboratory microcomputer.

Further experiments for determining the errors caused by surface

out-of-flatness and angular tilt in the non-sensitive direction are under consideration.

16
Contact Person at NBS

Robert Hocken

Automated Production Technology Division

301- 921-2556

or

William Gallagher

Automated Production Technology Division

301- 921-2216

17
SURFACE TEXTURE (1.8)

Description of Services

NBS provides measurement services in three categories: Instrument

calibration specimens (with regular geometric profiles); roughness

comparison (and other types of roughness specimens); and step height

specimens.

The property of surface roughness in the 10 pm R range and below

and heights up to 25 pm are measured by means of a minicomputer/stylus

instrument system. Using an interferometrically measured step, the

system is calibrated on each value of magnification employed during a measurement.

In measurements of roughness, surface profiles are taken according

to the American National Standard B46. 1*1978 using a 0.76 mm cutoff

length, and a traversing length of 3.8 mm. A number of other statistical

parameters and functions may be calculated from the stored profile data

including the rms roughness, average slope, average wavelength, skewness,

amplitude density function, autocorrelation function, and power spectral

density.

In step height measurements, a straight line is fitted by the

method of least squares to each side of the profile of the step and the

height is calculated from the position of these two lines.

The NBS calibration uncertainty for step height or R depends on a number of factors, the most important being the step or R

a value itself.

The uncertainties range from approximately .3 pm at a stejl height of 25

pm to .003 pm. Comparable uncertainties are achieved for measurements

of r . a Documentation

Precision Reference Specimens of Surface Roughness: Some Characteristics

of the Cali-Block, R. D. Young and F. E. Scire, J. Res. Natl. Bur.

Stand. (U.S.), 76C (Eng. and Instr.), Nos. 1 and 2, 21-23 (Jan. -June

1972).

Evaluation, Revision and Application of the NBS Stylus/Computer System

for the Measurement of Surface Roughness, E. C. Teague, Natl. Bur.

Stand. (U.S.), Tech. Note 902, 151 pages (Apr. 1976).

Surface Finish Measurements: An Overview, E. C. Teague, Soc. Manuf.

Eng., Tech. Pap. IQ75-137, 1-21 (1975).

The Measurement and Characterization of Surface Finish, R. D. Young and

E. C. Teague, Chapter 2 in Properties of Electrodeposits. Their

Measurement and Significance , R. Sard, H. Leidheiser, and F. Ogburn,

Eds., pp. 22-49 (Electrochemical Society, Princeton, NJ, 1975).

Uncertainties in Calibrating a Stylus Type Surface Texture Measuring

Instrument With an Interferometrically Measured Step, E. C. Teague,

Metrologia, 14, 39-44 (1979).

18
Measurements of Stylus Radii, T. V. Vorburger, E. C. Teague, F. E. Scire

and F. W. Rasberry, Wear, 57, 39-49 (1979).

FAST Facility Available for Engineering Needs, T. V. Vorburger, E. C. Teague and F. E. Scire, Dimensions/NBS, 62, 18-20 (Nov. 1978).

Optical Techniques for On-Line Measurement of Surface Topography, T. V. Vorburger and E. C. Teague, Precision Engineering, 3, 611 (1981).

Sinusoidal Profile Precision Roughness Specimens, E. C. Teague, F. E. Scire and T. V. Vorburger, Wear, 83, 61-73 (1982).

Three-Dimensional Stylus Profilometry, E. C. Teague, F. E. Scire, S. M. Baker and S. W. Jensen, Wear, 83, 1-12 (1982).

FASTMENU: A Set of FORTRAN Programs for Analyzing Surface Texture, T.

V. Vorburger, Natl. Bur. Stand. (U.S.), NBSIR 83-2703 (July 1982).

Training Programs

None.

Future Directions

None specified.

Contact Person at NBS

Theodore Vorburger

Mechanical Production Metrology Division

301-921-3838

19
IMAGE OPTICS AND PHOTOGRAPHY (1.9)

Description of Services

Microscopy resolution test charts conforming to ISO Standard 3334,

NMA Standard MS104-1972, and MIL-M-9868D, are available through the NBS

Office of Standard Reference Materials (SRM 1010a). Diffuse transmission

density is measured in accordance with ANSI Standard PH2. 19-1976.

Calibrated step tablets for photographic calibrations are available

through the NBS Office of Standard Reference Materials as SRM 1008.

45°/0° absolute visual reflection density is measured in accordance

with ANSI Standard PH2. 17-1977. Calibrated step tablets are available

through the Office of Standard Reference Materials as SRM 2061.

In special cases, measurements may be made by arrangement. Tablets

submitted for calibration must be free of scratches, fingerprints,

abrasions, and foreign matter and must have steps of uniform density.

Tablets not suitable as standards will not be accepted by NBS for

cal ibration.

Documentation

Basic Considerations of Densitometer Adjustment and Calibration, R. E. Swing, Natl. Bur. Stand. (U.S.), Report 10970 (Dec. 1972).

The Optics of Densitometry, R. E. Swing, Opt. Eng. , 12, No. 6, 185-198

(Nov. /Dec. 1973).

Basic Considerations of Densitometer Adjustment and Calibration, R. E. Swing, Natl. Bur. Stand. (U.S.), NBSIR 75-682, 18 pages (Feb. 3, 1975).

Order from NTIS as COM 75-10524.

Development of Dimensional Measurement Techniques from 1 to 10

Micrometers and Application to Optical Microscope Measurements, J. M. Jerke, Meeting of Society of Photographic Scientists and Engineers,

Proceedings (Feb. 1975).

An Improved Photographic Edge-Artifact , W. R. Smallwood and R. E. Swing,

Natl. Bur. Stand. (U.S.), NBSIR 76-1129, 49 pages (Aug. 1976). Order

from NTIS as PB 274712.

Training Programs

None.

Future Directions

None specified.

Contact Person at NBS

Jack Hsia

Radiometric Physics Division

301-921-2791

20
ACOUSTIC MEASUREMENTS (2.1)

Description of Services

NBS provides calibration services for special microphones, acoustic

emission transducers, ultrasonic transducers and ultrasonic reference

blocks. Pressure calibrations are performed on type-L (one inch)

microphones satisfying the requirements of American National Standard

SI. 12. 1967 (R1977), Specifications for Laboratory Standard Microphones

and its impending revision. Pressure calibrations are reported in terms

of open-circuit voltage per unit sound pressure applied uniformly to the

diaphragm. The open-circuit voltage at the electrical terminals of a microphone may be influenced by stray capacitances evident at these

terminals. For type-L microphones, these capacitances are defined by

the geometrical configuration of the ground shield. If the ground

shield dimensions are not adhered to in making use of the response

levels reported by NBS, errors may result. Pressure calibrations of

type-L microphones exhibit typical uncertainties of approximately 0.1 dB or less at frequencies from 50 Hz to 8 kHz, 0.2 dB or less at frequencies

from 8 kHz to 20 kHz.

Since American National Standards Institute publications SI. 10. 1966

(R1976) and SI. 12. 1967 (R1977) were issued, certain types of half-inch

diameter precision microphones have attained widespread use. Therefore,

NBS has developed procedures for determining the pressure response

levels of half- inch microphones by comparison with NBS type-L standard

microphones, which in turn are calibrated periodically by the reciprocity

technique.

The free-field response levels of certain type-L microphones (e.g.

Western Electric type 640AA condenser microphones or equivalent) can be

computed from pressure response levels reported by NBS. However,

certain precautions must be taken and there is some degradation in

accuracy. Therefore, for the most demanding free-field measurement

requirements NBS offers a calibration service for determining the

free-field response levels for half-inch microphones. The calibrations

are made at normal incidence over the frequency range of 2.5 kHz to

20 kHz. They are reported in terms of open-circuit voltage per unit

sound pressure of a plane progressive wave whose direction of

propagation is normal to the plane of the diaphragm. The calibrations

are performed in a well characterized anechoic chamber. A typical

uncertainty in this calibration is approximately 0.15 dB at each

frequency within the range of 2.5 kHz to 20 kHz. For the most precise

free-field measurements, it is recommended that the customer contact the

person listed for recommendations prior to submitting the microphone to

NBS for calibration.

Special acoustical measurement services are available by special

arrangement. These services may include extended frequency ranges,

additional data points and calibration of certain piston phones and

acoustic calibrators. NBS has a large, general purpose anechoic chamber

available for special calibrations requiring such a facility. The

frequency-dependent and position-dependent acoustical performance of

this chamber, including extremely low background noise, has been

carefully controlled during design and construction.

21
The NBS acoustic emission transducer calibration provides the

voltage output of a transducer per unit of motion (displacement or velocity) of the mounting surface as a function of frequency. The

calibration is based upon the normal component of motion which would

occur in the absence of the transducer. The method of the test is as follows: a step function of "point" force is generated on the surface

of a large steel block by breaking a glass capillary.

The transducer under test and the NBS standard capacitive transducer

are located on this same surface and are equidistant from the source. Both transducers experience the motion of the seismic surface pulse

generated by the step function force. The transient voltage outputs

from both transducers are recorded and analyzed for frequency content.

The frequency response of the transducer under test is obtained by

dividing the spectral amplitude from the transducer under test by that

from the standard transducer, frequency by frequency. The calibration

is absolute, since the sensitivity of the standard transducer is known.

Results of the calibration are obtained as magnitude and phase of

the sensitivity of the transducer under test at discrete frequencies,

f = 9765. 625n (Hz), where n = 1,2,3. . . The customer is provided with

tfie results in the form of graphs and magnitude and phase. These are piecewise linear functions constructed through the data points. Within

the valid range of 0.1 MHz to 1 MHz, the uncertainty is approximately

10%. At the option of the customer, the results will be given with

respect to normal displacement or velocity of the mounting surface, and

also at the option of the customer, the results will be on a linear

magnitude scale or on a decibel scale.

Measurements of total ultrasonic forward power radiated into a water load are offered for the purpose of characterizing ultrasonic

systems and transducers. Ultrasonic systems are characterized by

measurement of output under operating conditions specified by the

customer. Transducers for which the continuous-wave electrical input

voltage can be accurately and reproducibly measured are characterized by

a radiation conductance determined from measurements of input voltage

and output power. A typical calibration report for an ultrasonic system

provides the results of at least three measurements of output power for

each operating condition specified. Calibration reports for transducers

typically present a single value of radiation conductance derived from

at least 15 measurements of output power spanning an appropriate range

of power. Equipment is available for the measurement of both

continuous-wave and pulsed ultrasonic power.

Continuous-wave ultrasonic power is measured using a modulatedradiation force balance. Output power is determined from the force

required to arrest the motion of a conical target which diverts the

output beam of the transducer under test into a bank of absorbers.

Because the rf input voltage to the transducer is amplitude-modulated,

the motion of the target is oscillatory and sensitive ac techniques can

be used for null detection. The nulling force is generated by an independently calibrated electromagnetic device for which absolute

transfer characteristics are known under static conditions. Absolute

n
power can thus be measured at spot frequencies between 1 MHz and 20 MHz.

The overall uncertainty varies from 2.2% at 1 MHz to 7.6% at 20 MHz.

These estimates of uncertainty apply to measurements made at power

levels ranging from a few milliwatts to a few watts; the minimum

detectable power is about 10 microwatts while high-power measurements

are limited by the onset of cavitation in the water load. Sweptfrequency measurements of relative transducer output can be made by

recording the error signal of the unbalanced detector. Although the

results do not constitute absolute measurements, swept-frsquency tests

have been found useful in the assessment of overall transducer performance and the determination of frequencies suitable for absolute

measurements. Transducers of diameter no greater than 45 mm can be

tested in this apparatus.

Pulsed ultrasonic power is measured using a special designed

calorimeter. With pulsed excitation, only ultrasonic systems comprising

a transducer and an electrical driver can be tested. Transducers by

themselves cannot be independently characterized with pulsed drive

waveforms since the electrical input signals cannot at present be

adequately measured or characterized. Power levels ranging from 1 mW to

several watts at frequencies between 1 MHz and 15 MHz can be measured

with an overall uncertainty less than (7% +0.2 mW). Transducers with

diameters as great as 26 mm can be accommodated. Measurements of

continuous-wave power are also possible with the calorimeter. The

length of its response time precludes swept- frequency tests.

Additional services offered include consultation, customized

testing, and the lending of air-backed transducers for the purpose of

transferring power measurements. Quartz transducers characterized by

radiation conductance and thus suited for the reproduction of arbitrary

power levels are available for frequencies of 2 MHz, 3 MHz and 5 MHz and can be specially calibrated for operation at odd overtones. Lithium

niobate transducers with built-in circuitry allowing the field user to

reproduce prearranged power levels while measuring only dc voltage are available for use at frequencies below 20 MHz approximated by odd

multiples of 0.5 MHz.

The ultrasonic response of 7075 aluminum alloy reference blocks of

0.50 inch and greater metal path distances is determined relative to an NBS interim reference standard. The immersion, pulse, echo,

longitudinal wave, 5 MHz quartz transducer testing system defined in the

ASTM E-127 calibration document is used with some procedural

modifications. An NBS developed procedure is used where the interim

reference standards are calibrated along with the customer's blocks.

System precision and stability over time are provided by the set of

check standard blocks with flat-bottom hole sizes of 3, 5, and 8/64 inch

diameter. Standard deviation data, representing random errors associated

with the NBS system, are provided for the respective block and hole sizes

The plus or minus two standard deviation uncertainty levels range from

about 3 to 10 percent of block response, depending on the block and hole

sizes of the respective check standards. A comparison of the customer's

block value to the data base of all blocks measured by NBS is also

avai lable.

23
Response following the procedures of the ASTM Recommended Practice

E-127 can also be determined. In addition, the response of some blocks

with metal path distances less than 0.50 inch can be obtained by special

arrangement. Where special services are required, it is recommended

that the customer contact the person listed at the end of this section

for recommendations and to discuss any special requirements.

Documentation

Specifications for Laboratory Standard Microphones, American National

Standards Institute, SI. 12-1967 (R1976), New York, N.Y.

Method of Calibration of Microphones, American National Standards

Institute, SI. 10-1966 (R1976), New York, N.Y.

Calibrations of Microphones, Vibration Pickups, and Earphones, R. K. Cook, S. Edelman, and W. Koidan, J. Audio Eng. Soc. , 13, No. 4 (Oct.

1965).

Method of Measurement of E'/I 1 in the Reciprocity Calibration of

Condenser Microphones, W. Koidan, J. Acoust. Soc. Am., 32, No. 5, 611

(May 1960).

Hydrogen Retention System for Pressure Calibration of Microphones in

Small Couplers, W. Koidan, J. Acoust. Soc. Am., 35, No. 4, 614 (Apr.

1963).

Free-Field Correction for Condenser Microphones, W. Koidan and D. S. Siegel, J. Acoust. Soc. Am., 36, No. 11, 2233-2234 (Nov. 1964).

Calibration of Standard Condenser Microphones: Coupler Versus

Electrostatic Actuator, W. Koidan, J. Acoust, Soc. Am., 44, No. 5,

1451-1453 (Nov. 1968).

Calibration of Laboratory Condenser Microphones, V. Nedzelnitsky, E. Burnett, and W. Penzes , Proceedings of the 10th Transducer Workshop,

Transducer Committee, Telemetry Group, Range Commanders Council,

Colorado Springs, CO (June 1979).

Traceability of Acoustical Instrument Calibration to the National Bureau

of Standards, V. Nedzelnitsky, Proc. INTER-NOISE 80, II, Dec. 8-10,

1980, Miami, FL, Maling, G. C. , Jr., ed. , Poughkeepsie, NY; Noise

Control Foundation, 1043-1046 (1980).

Wedge Design for the National Bureau of Standards Anechoic Chamber, W. Koidan, G. R. Hruska, and M. A. Pickett, J. Acoust. Soc. Am. , 52, No. 4

(Part 1), 1071-1076 (1972).

Acoustical Properties of the National Bureau of Standards Anechoic

Chamber, W. Koidan and G. R. Hruska, J. Acoust. Soc. Am. , 64, No. 2

(Aug. 1978).

Acoustic Emission: Some Applications of Lamb's Problem, F. R. Breckenridge, C. E. Tschiegg, and M. Greenspan, J. Acoust. Soc. Am., 57,

No. 3, 626-631 (Mar. 1975).

24
Characterization and Calibration of Acoustic Emission Sensors, N. N. Hsu

and F. R. Breckenridge, Matls. Eval . , 39, No. 1, 60-68 (Jan. 1981).

Surface-Wave Displacement: Absolute Measurements Using a Capacitive

Transducer, F. R. Breckenridge and M. Greenspan, J. Acoust. Soc. Am.

69, No. 4, 1177-1185 (Apr. 1981).

Calibration and Sensor Activities, D. G. Eitzen, F. R. Breckenridge, R. B. Clough, E. R. Fuller, N. N. Hsu, and J. A. Simmons, Chapter 2.0 in

Fundamental Developments for Quantitative Acoustic Emission Measurements,

EPRI NP-2089, Research Project 608-1, Palo Alto, CA, Electric Power

Research Institute, 2-1-2-52 (Oct. 1981).

Acoustic Emission Transducer Calibration by Means of the Seismic Surface

Pulse, F. R. Breckenridge, J. Acoust. Emission, 1, No. 2 (Apr. 1982).

Calibration of Quartz Transducers as Ultrasonic Power Standards by an Electrical Method, T. L. Zapf, 1974 Ultrasonics Symposium Proceedings,

IEEE Cat. 74, CH0896-ISU (1974).

Ultrasonic Calorimeter for Beam Power Measurements from 1 to 15

Megahertz, T. L. Zapf, M. E. Harvey, N. T. Larsen, and R. E. Stoltenberg, 1976 Ultrasonics Symposium Proceedings, IEEE Cat. 76,

CH1120-5SU (1976).

Ultrasonic Calorimeter for Beam Power Measurements, T. L. Zapf, M. E. Harvey, N. T. Larsen, and R. E. Stoltenberg, Natl. Bur. Stand. (U.S.),

Tech. Note 686, 31 pages (Sept. 1976).

Ultrasonic Transducer Power Output by Modulated Radiation Pressure, M. Greenspan, F. R. Breckenridge, and C. E. Tschiegg, J. Acoust. Soc. Am.

63, No. 4, 1031-1038 (Apr. 1978).

Ultrasonic Transducer Power Output by Modulated Radiation Pressure (with

details), M. Greenspan, F. R. Breckenridge, and C. E. Tschiegg, Natl.

Bur. Stand. (U.S.), NBSIR 78-1520, 40 pages (July 1978).

Ultrasonic Transducer Characterization at the NBS, E. R. Miller and D. G. Eitzen, IEEE Trans. Sonics and Ultrasonics, SU-26, No. 1, 28-37 (Jan.

1979).

Procedures for the Calibration of ASTM E127-Type Ultrasonic Reference

Blocks, D. J. Chwirut, G. F. Sushinsky, and D. G. Eitzen, Natl. Bur.

Stand. (U.S.), Tech. Note 924, 38 pages (Sept. 1976).

Standard Practice for Fabricating and Checking Aluminum Alloy Ultrasonic

Standard Reference Blocks, E-127-81, in Annual Book for ASTM Standards,

Part II, Philadelphia, PA, American Society for Testing and Materials

(1982).

Improved Ultrasonic Standard Reference Blocks, G. F. Sushinsky, D. G.

Eitzen, D. J. Chwirut, C. J. Bechtoldt, and A. W. Ruff, Natl. Bur.

Stand. (U.S.), NBSIR 76-984, 128 pages (Nov. 1976).

25
The Evaluation of Search Units Used for Ultrasonic Reference Block

Calibrations, D. J. Chwirut and G. D. Boswell, Natl. Bur. Stand. (U.S.),

NBSIR 78-1454, 25 pages (Feb. 1978).

Recent Improvements to the ASTM-Type Ultrasonic Reference Block System,

D. J. Chwirut, Natl. Bur. of Stand. (U.S.), NBSIR 79-1742, 50 pages

(Feb. 1979).

An Assessment of Ultrasonic Reference Block Calibration Methodology, G.

V. Blessing, Natl. Bur. Stand. (U.S.), NBSIR 83-2710, 23 pages (June

1983).

Training Programs

None.

Future Directions

None specified.

Contact Person at NBS

Victor Nedzelnitsky

Mechanical Production Metrology Division

301-921-3607

or

Donald Eitzen

Mechanical Production Metrology Division

301-921-3646

26
VIBRATION MEASUREMENTS (2.2)

Description of Services

NBS calibrations of vibration exciters and pickups are performed by

comparison with the response characteristics of NBS standards or by

absolute measurements. The measurand is the transfer function of the

instrument, usually referred to as the sensitivity. For a pickup it is

the ratio of the electrical output to a mechanical input. In the case

of an accelerometer, the U.S. practice has been to express the output in

millivolts, and the input, in units of g, the standard acceleration of

free fall. The acceleration sensitivity is then given in mV/g. Other

units are sometimes used, for example, the calibration of piezoelectric

and pi ezoresi stive accelerometers without signal conditioners is stated

in pi cocoulombs per g (pC/g).

The calibration of an accelerometer is given as the sensitivity of

the transducer at the discrete frequencies at which the measurements are made and is reported in tabular form. Because sensitivity is a phasor

quantity, representable as a complex number, a complete calibration

consists of a measurement of both magnitude and phase of the

sensitivity. Only the magnitude of the sensitivity is usually reported.

However, the phase component can be furnished on request.

The NBS also offers several standardized vibration calibration

services designed to meet the needs of the users. Calibrations are furnished at frequencies from 2 Hz to 13,000 Hz and accelerations from

0.2 g to 10 g, depending on frequency. Calibrations at other

frequencies and accelerations can be furnished by pre-arrangement.

The NBS vibration standards have been calibrated by reciprocity and

interferometric techniques, two independent and absolute methods. Their

calibration is periodically checked using both techniques. The use of

these standards in the calibration of stable transducers furnish calibration data with a typical uncertainty of from one to three percent over

the frequency range.

Documentation

Calibration of Vibration Pickups by the Reciprocity Method, S. Levy and

R. R. Bouche, J. Res. Natl. Bur. Stand. (U.S.), 57, No. 4, 227-243 (Oct.

1956).

Calibration of Vibration Pickups at Large Amplitudes, E. Jones, S. Edelman, and K. S. Sizemore, J. Acoust. Soc. Am. , 33, No. 11, 1462-1466

(Nov. 1961).

Electrodynamic Vibration Standard with a Ceramic Moving Element, T. Dimoff, J. Acoust. Soc. Am., 40, No. 3, 671-676 (Sept. 1966).

Improved Transfer Standard for Vibration Pickups, E. Jones, D. Lee, and

S. Edelman, J. Acoust. Soc. Am., 41, No. 2, 354-357 (Feb. 1967).

27
Accelerometer Resonances Affect Vibration Measurement, E. T. Pierce, 0.

W. Price, S. Edelman, and E. Jones, J. Environ. Sci., 10, No. 6, 17-21

(Dec. 1967).

Piezoelectric Shakers for Wide- Frequency Calibration of Vibration

Pickups, E. Jones, B. Yelon, and S. Edelman, J. Acoust. Soc. Am., 46,

No. 6, 1556-1559 (June 1969).

An Automated Precision Calibration System for Accelerometers, B. F. Payne, Instrum. Soc. Am. 17th National Aerospace Instrumentation

Symposium (May 1971).

A Systematic Study of Vibration Transfer Standards--Mounting Effects, R. S. Koyanagi , J. D. Pollard, and J. D. Ramboz, Natl. Bur. Stand. (U.S.),

NBSIR 73-291, 42 pages (Sept. 1973).

Piezoelectric Accelerometer Low-Frequency Response by Signal Insertion

Methods, R. S. Koyanagi and J. D. Pollard, Natl. Bur. Stand. (U.S.),

NBSIR 74-597, 33 pages (May 1975).

Shock Calibration of Accelerometers, C. Federman, W. Walston, and J. Ramboz, Minutes of the 8th Transducer Workshop: Telemetry Group,

Inter-Range Instrumentation Group, Range Commanders Council, WrightPatterson AFB, OH (Apr. 1975).

Accelerometer Calibration at the National Bureau of Standards, B. F. Payne, R. S. Koyanagi, C. Federman, and E. Jones, 21st Int. Instrumentation Symposium ASD/TMD , May 19-21, 1975, Philadelphia, PA, 1-17 (1975).

Development of a Low-Frequency-Vibration Calibration System, R. S. Koyanagi, Exp. Mech. , 15, 443-448 (Nov. 1975).

Absolute-Calibration of Accelerometers at the National Bureau of

Standards, B. F. Payne and M. R. Serbyn, Proc. 10th Transducer Workshop:

Telemetry Group, Inter-Range Instrumentation Group, Range Commanders

Council, June 12-14, 1979, Colorado Springs, CO, 136-144 (1979).

The Application of Back-to-Back Accelerometers to Precision Vibration

Measurements, B. F. Payne, J. Res. Natl. Bur. Stand. (U.S.), 88, No. 3,

171-174 (May- June 1983).

A Real-Time Active Vibration Controller, M. R. Serbyn and W. B. Penzes,

ISA Transactions, 21, No. 3, 55-59 (1982).

An Automated System for the Measurement of Pickup Sensitivity, B. F. Payne and M. R. Serbyn, NCSL 1983 Workshop and Symposium Proceedings,

II-ll.l - 11-11.22 (July 1983).

Training Programs

None.

Future Directions

None specified.

28
Contact Person at NBS

Beverly Payne

Mechanical Production Metrology Division

301- 921-3607

29
HUMIDITY MEASUREMENTS (2.3)

Description of Services

The NBS provides calibration services for a wide variety of

humidity-measuring instruments. Calibrations are performed by

subjecting the instrument under test to atmospheres of known moisture

content produced by the NBS two-pressure humidity generator. The

instruments and ranges of calibration are listed below.

Dew-Point Hygrometers : Dew-point hygrometers can be calibrated

over the dew/frost-point range of 80 to -80 °C.

Electric Hygrometers : Hygrometers classified under this category

are sensors which sorb water vapor as a function of relative humidity;

associated with this sorption is a corresponding change in an electric

parameter (that is, resistance, capacitance). The range of calibration

is 3 to 98 percent relative humidity over the temperature range -55 to

80 °C.

Psychrometers : A limited number of types of wet-dry bulb hygrometer

(aspirated psychrometers) can be calibrated at NBS. The contact person

should be consulted for the special features of the psychrometer which

are necessary before the instrument can be calibrated at NBS.

Coulometric Hygrometers : Coulometric hygrometers are devices which

electrolyze water into gaseous oxygen and hydrogen by the application of

a voltage in excess of the thermodynamic decomposition voltage for water

and measure the electrolysis current. The range of calibration is 1 to

31,000 ppm (parts per million) by volume.

Pneumatic Bridge Hygrometers : Pneumatic bridge hygrometers are instruments which measure the variation of the pressure drop across two

combinations of nozzles, operating at critical flow, with a desiccant

between one pair of nozzles. The range of calibration in mixing ratio

(gram water vapor/gram dry air) is 0.0005 to 0.015.

Documentation

The NBS Standard Hygrometer, A. Wexler and R. W. Hyland, Natl. Bur.

Stand. (U.S.), Monogr. 73, 35 pages (May 1964).

The NBS Two-Pressure Humidity Generator, Mark 2, S. Hasegawa and J. W. Little, J. Res. Natl. Bur. Stand. (U.S.), 81A (Phys. and Chem. ), No. 1,

81-88 (Jan. -Feb. 1977).

Vapor Pressure Formulation for Water in Range 0 to 100 °C. A Revision,

A. Wexler, J. Res. Natl. Bur. Stand. (U.S.), 80A (Phys. and Chem.), Nos.

5 and 6, 775-785 (Sept. -Dec. 1976).

Vapor Pressure Formulation for Ice, A. Wexler, J. Res. Natl. Bur. Stand.

(U.S.), 81A (Phys. and Chem.), No. 1, 5-20 (Jan. -Feb. 1977).

30
A Correlation for the Second Interaction Vi rial Coefficients and

Enhancement Factors for Moist Air, R. W. Hyland, J. Res. Natl. Bur.

Stand. (U.S.), 79A (Phys. and Chem.), No. 4, 551-560 (July-Aug. 1975).

Training Programs

None.

Future Directions

Efforts are underway to automate the acquisition of the generator's

pressure and temperature data and the indication data from the

instrument under test where possible. Certain of the control functions

of the generator will also be automated to reduce the amount of labor

currently needed to perform a calibration. In addition to the

automation of the generator, the pressure instruments used in the

generator will be replaced since maintenance at the required level of

performance is becoming necessary. Comparison of the generator's gas

stream with the primary standard gravimetric hygrometer is planned to

begin in the next two years. This is an extremely laborious task and is

expected to take approximately one year to complete. The gravimetric

hygrometer is not currently operational and must be to do the

compari son.

Contact Person at NBS

Saburo Hasegawa

Chemical Process Metrology Division

301-921-2794

31
CALIBRATION OF FORCE TRANSDUCERS AND FORCE MEASUREMENT SYSTEMS (2.5)

Description of Services

NBS provides calibration services for force measuring devices by

applying known forces, either tension or compression, to the elastic

device and recording the sensed deformation. Practically all of the

devices calibrated are either providing rings or load cells. The

deformation of proving rings is usually measured by means of a micrometer screw and vibrating reed which are an integral part of the

device. An electrical output is usually provided from load cells to

indicate the deformation caused by the application of a force. The

calibration report gives the measured electrical output or measured

deformation of a known applied force. When the calibration calls for

reading and electrical output, the output can be measured by either a readout device furnished by the customer, in which case the sensor and

the readout device are calibrated as a unit and the calibration is only

valid when they are used together; or the output is measured directly

and the calibration is given in terms of the electrical output of the sensor directly.

Tension or compression calibrations in the range of 10 Ibf to

1.000.

000 Ibf are performed using deadweight machines. NBS has six such

deadweight machines with maximum capacities of 500; 6,100; 25,300;

112,000; 300,000; and 1,000,000 Ibf. The three larger machines allow

the force applied to the unit being calibrated to be incremented or decremented without having to go to zero load between force applications. When using the three smaller machines it is necessary to go to zero load before the load is changed. The estimated uncertainty of the

vertical component of the applied force is 20 parts per million.

Comparison calibrations in the range of 10,000,000 Ibf to

12.000.

000 Ibf are performed in a universal testing machine. In this

case, the system being calibrated is loaded in series with one or more

load cells that have been previously calibrated in a deadweight machine.

NBS is prepared to perform special tests and calibrations in some

cases. These should be discussed with NBS before any such tests or calibrations are ordered.

Documentation

Uncertainties Associated with Proving Ring Calibration, T. E. Hockersmith and H. H. Ku, Preprint No. 12.3-2-64: ISA Conference, Oct.

12- 15 , 1964 .

Absolute Value of g at the National Bureau of Standards, D. R. Tate,

Natl. Bur. Stand. (U.S.), Monogr. 107, 24 pages (June 1968).

Gravity Measurements and the Standards Laboratory, D. R. Tate, Natl.

Bur. Stand. (U.S.), Tech. Note 491, 10 pages (Aug. 1969).

32
Studies of Calibration Procedures for Load Cells and Proving Rings as Weighing Devices, G. B. Anderson and R. C. Raybold, Natl. Bur. Stand.

(U.S.), Tech. Note 436, 22 pages (Jan. 1969).

Universal Testing Machine of 12-Mi 1 1 ion-1 bf Capacity at the National

Bureau of Standards, A. F. Kirstein, Natl. Bur. Stand. (U.S.), Spec.

Publ. 355, 14 pages (Sept. 1971).

A Study of the National Force Measurement System, D. E. Marlowe, Natl.

Bur. Stand. (U.S.), NBSIR 75-929, 40 pages (June 1975).

Inter laboratory Comparison of Force Calibrations Using ASTM Method

E74-74. Phase I, R. W. Peterson and R. L. Bloss, Natl. Bur. Stand.

(U.S.), NBSIR 76-1145, 35 pages (Aug. 1976).

Characterizing the Creep Response of Load Cells, R. A. Mitchell and S. M. Baker, VDI-Berichte (312), 43-48 (1978).

Force Sensor-Machine Interaction, R. A. Mitchell and P. E. Pontius,

Proceedings of the 27th International Instrumentation Symposium (ISA),

Indianapolis, IN, Instrumentation in the Aerospace Industry, 27, 225-232

(1981).

Inherent Problems in Force Measurements, P. E. Pontius and R. A. Mitchell, Exper. Mech. , 22, No. 3 (Mar. 1982).

Training Programs

None.

Future Directions

None specified.

Contact Person at NBS

Richard Mitchell

Mechanical Production Metrology Division

301-921-3884

33
FLUID QUANTITY AND FLOW RATE METERS (2.7)

Description of Services

NBS provides calibration services for flow meter systems which

include a flow meter and pertinent adjacent tubing and readout equipment.

Flow meter systems having demonstrated precision and temporal

stability commensurate with the quality of the calibrations are accepted

for calibration. Calibration tests usually include five different flow

rates, although additional rates can be included on request. At each

flow rate, 10 observations are made.

Facilities are maintained for flow rate (volumetric and mass)

measurements for fluids, using water, air, and a stable hydrocarbon as test fluids. The ranges of flow rates used in calibrations are: 1-10,000 gal /min for water; up to 150 cubic ft/mi n for air in the small

gas flow facility, and 150-3000 cubic ft/mi n for air in the large gas

flow facility; and up to 200 gal /min for hydrocarbons.

Documentation

Introduction to Liquid Flow Metering and Calibration of Liquid Flowmeters,

L. 0. Olsen, Natl. Bur. Stand. (U.S.), Tech. Note 831, 60 pages (June

1974).

Flow Measurement: Procedures and Facilities at the National Bureau of

Standards, F. W. Ruegg and M. R. Shafer, (Proc. Symp. Flow Measurement,

San Francisco, CA, Jan. 19-22, 1970). Chapter in ASHRAE (Amer. Soc.

Heat Refrig. Air-Cond. Eng.), Bull. Flow Measurement Part 1, SF70-7, 1-8

(1972).

Practical Considerations for Gas Flow Measurement, M. R. Schafer, Jr.

and D. W. Baker, Proc. 3rd Annual Precision Measurement Association

Metrology Conf. , National Bureau of Standards, Gaithersburg, MD, June

17-18, 1970, 1, 187-227 (Precision Measurements Association, Burbank,

CA, 1970).

Gas Flow Measurement by Collection Time and Density in a Constant

Volume, L. Olsen and G. Baumgarten, Symposium on Flow, Its Measurement

and Control in Science and Industry, ISA, 1, Part 3, 1287 (1972).

Evaluation of a Low Flow Generator and Calibrator as a Flow Measurement

Standard, G. Baumgarten, Natl. Bur. Stand. (U.S.), Technical Report

10921 (1972).

The National Measurement System for Fluid Flow, W. C. Haight, P. S. Klebanoff, F. W. Ruegg, and G. Kulin, Natl. Bur. Stand. (U.S.), NBSIR

75-930, 66 pages (Aug. 1976). Order from NTIS as PB258250.

A Laboratory Study of Turbine Meter Uncertainty, G. E. Mattingly, P. E. Pontius, H. H. All ion, and E. F. Moore, Natl. Bur. Stand. (U.S.), Spec.

Publ . 484 (Oct. 1977).

34
Training Programs

None.

Future Directions

The key parameters measured in each device calibration are the

transit time, volume (stroke), pressure, and temperature. Improvements

are planned for each parameter measurement which will enhance the

capability to perform the calibration measurements and, where possible,

automate the calibration measurements and decrease the uncertainty in

the measured variables.

Pressure Measurement - All pressure measurement will be changed to use transducers which may be interfaced to the microprocessor system

used for data acquisition and control of the test. Direct ties to the

pressure standard will be maintained using dead weight testing devices

which have been calibrated by the pressure group. Response characteristics

of each transducer will be kept in a database to provide a history of

its performance.

Temperature Measurement - Contact thermometry used for determination

of gas temperatures either in the collection volumes, displacers, or in

the gas stream passing through the meter, will be characterized using a platinum resistance thermometer which has a history of calibration by

the temperature group. Either thermocouples or resistance thermometers

will be used in the initial automation and documentation of the laboratory.

Since contacting methods measure the temperature at a point, the

question of average temperature of the gas contained in the displaced

volume is one of concern. An acoustic thermometry approach will be

explored to obtain an improved measurement of the average gas

temperature in the displacers.

Volume Measurement - To improve the measurement of the volume of

gas displaced, a laser interferometric technique will be used to measure

the stroke of the displacer. This technique will be used with each of

the five mercury-sealed piston provers and with the bell gasometers.

The device is easily moved from one system to the other by moving the

laser head and using multiple sets of interferometer optics. The

Hewlett-Packard laser interferometer will be used with corner cubes as the reflectors. Each piston/bell will have a cube attached with the

laser/interferometer block held stationary. Measurement of the diameter

of the cylinders and of the bells will be done using established length

metrology techniques. For the bell gasometers the outer diameter will

be measured using strapping tapes. The volume of oil displaced by the

bell material will be determined volumetrically. The inner diameter of

each cylinder will be measured using an air gauging technique. Both

methods will be tied to length standards.

Time Measurement - Time interval measurement will be done by

modification of a counter register of the laser interferometer system.

A 100 KHz clock will be used to drive the counter during the time

interval of the displacer movement. This frequency will be compared

directly with the standard frequency available on the NBS site. Th-s

35
technique allows the simultaneous triggering of the counter registers

used for the displacement measurement and the timing measurement.

Calibration measurements on high range flow meters are based on the use of a set of working standards which are flow nozzles operated under

critical conditions, i.e., at sonic velocity in the throat of the

nozzle. Determination of the mass flowrate through these nozzles is

based upon measured discharge coefficients. Measurement of the discharge

coefficient for each nozzle over the range of throat Reynolds numbers

used has been done in PVT experiments in which the gas flowing through

the nozzle is diverted into the collection tank of the loop for a measured period of time. At this time the collection tank is of unknown

volume since the piping associated with it has been modified, adding

additional contained volume. Efforts are underway to redetermine the

collection tank volume. Automation of the data acquisition system

associated with this flow measurement facility is underway.

Plans are underway to upgrade the calibration service for hydrocarbon flow meters by improving laboratory capabilities through the use of new technology using positive displacement, piston/cyl inder devices

(commonly called piston provers) which promise considerably improved

accuracy in the characterization of flow metering devices.

Contact Person at NBS

James Whetstone

Chemical Process Metrology Division

301- 921-3681

36
AERODYNAMICS (2.9)

Description of Services

NBS provides calibrations of air speed measuring instruments.

Measurements are performed in two high quality wind tunnels covering the

air speed range of 4-4900 meters per minute (0.1-180 mph).

The low velocity wind tunnel has a test section with dimensions 0.9

meter by 0.9 meter and covers an air speed range of 4-540 meters per

minute (0.1-20 mph). The velocity standard in this wind tunnel is a laser velocimeter.

The high velocity wind tunnel has two test sections. The first of

these has dimensions of 1.5 meters by 2.1 meters and covers an air speed

range of 2-46 meters per second (4-100 mph). The second test section

has dimensions of 1.2 meters by 1.5 meters and covers an air speed range

of 4-82 meters per second (9-180 mph).

Air density values in the tunnels are computed from pressure and

temperature measurements in the tunnel's settling chamber. These

measurements are made using a recently refurbished mercury barometer and

thermi stors.

Documentation

Experimental Investigation of Drag on a Compliant Surface, J. M. McMichael,

P. S. Klebanoff, and N„ E. Mease, Viscous Flow Drag Reduction, edited by

Gary R. Hough, 72 of Progress in Astronautics and Aeronautics, 1980.

Low Velocity Performance of a Ball Bearing Vane Anemometer, L. P. Purtell, Natl. Bur. Stand. (U.S.), NBSIR 78-1485, 19 pages (June 1978).

Order from NTIS.

A Low-Velocity Airflow Calibration and Research Facility, L. P. Putrell

and P. S. Klebanoff, Natl. Bur. Stand. (U.S.), Tech. Note 989, 18 pages

(Mar. 1979). Order from NTIS. Also available from Supt. of Documents,

Washington, DC, SD Stock No. SN003-003-02038-9.

Low Velocity Performance of Anemometers, L. P. Purtell, Natl. Bur.

Stand. (U.S.), NBSIR 79-1759, 168 pages (May 1979). Request from Bureau

of Mines.

Low Velocity Performance of a Magnetic Pick-Up Vane Anemometer, L. P. Purtrel 1 , Natl. Bur. Stand. (U.S.), NBSIR 79-1566, 34 pages (Dec. 1978).

Request from Bureau of Mines.

Training Programs

None.

Future Directions

Efforts are underway to develop a full set of documentation for the

measured parameters to infer the uncertainty in the calibration measurement

37
themselves. The mercury barometer used for pressure measurements will

be compared with the standard maintained by the NBS Pressure Group

utilizing a transfer standard available from that group. The currently

used thermometers will be discarded and platinum resistance elements or new thermocouples will be substituted. These will have been calibrated

against a standard PRT as are those used for gas flow measurements.

Contact Person at NBS

Norman Mease

Chemical Process Metrology Division

301- 921-3684

38
RESISTANCE MEASUREMENTS (3.1)

Description of Services

This service provides for calibrations of primary standard

resistors in the range from 0.0001 ohms to 1 teraohm, high-current

standards of resistance (shunts) up to 0.1 ohms, and resistance

measurements assurance program (MAP) transfers. One-ohm resistance

standards of the Thomas type are calibrated directly against the five

NBS Thomas resistors used to maintain the legal ohm. All others are calibrated by comparison with NBS working standards of the same nominal

value, except at the two ends of the scale, where ten to one ratios may

be employed. These working standards are calibrated in terms of the

primary group of Thomas resistors through the use of resistance networks

especially designed to attain 10:1 and 100:1 ratios with accuracies

better than 0.01 ppm.

Shunts are calibrated by comparison with special low- valued standards

resistors designed to maximize heat dissipation and kept in stirred,

temperature-controlled oil. Currents of up to 1000 ampers may be

handled directly.

Resistance MAP transfers are generally carried out at one of three

levels: one ohm, ten-thousand ohms, or ten to one hundred megahoms. In

the first two cases, commercial standard resistors (generally four) are used as transport standards; in the latter case, use is made of NBSconstructed resistors based on tested thin-film resistors. These

services are intended to provide traceability at the highest attainable

accuracies and therefore involve a high degree of interaction between

NBS and client personnel.

Documentation

Automated NBS l-0hm Measurement System, K. R. Baker and R. F. Dziuba,

IEEE Transactions on Instrumentation and Measurement, IM-32, No. 1, 154

(Mar. 1982).

Determination of the Fine-Structure Constant Using GaAs-Al (x) Ga (1-x)

as Heterstructures , D. C. Tusui, A. C. Gossard, B. F. Field, M. E. Cage, and R. F. Dziuba, Phys. Rev. Ltrs. , 48, 3 (1982).

Measurement of the Quantized Hall Steps in Silicon at the PPM Level, R. J. Wagner, C. F. Lavin, M. E. Cage, R. F. Dziuba, and B. F. Field,

Surface Science, 113, 10 (1982).

An Integrated System for the Precision Calibration of Four-Terminal

Standard Resistors, T. E. Wells and E. F. Gard, IEEE Transactions on Instrumentation and Measurement, IM 20, No. 4, 253 (Nov. 1971).

Calibration Procedures for Direct Current Apparatus, P. Brooks, Natl.

Bur. Stand. (U.S.), Monogr. 39 (Mar. 1962).

Measurement of Multimegohm Resistors, A. H. Scott, J. Res. Natl. Bur.

Stand. (U.S.), 50, No. 3 (Mar. 1953).

39
Precision Resistors and Their Measurement, J. L. Thomas, Natl. Bur.

Stand. (U.S.), Circular 470 (Oct. 1948).

Methods, Apparatus, and Procedures for the Comparison of Precision

Standard Resistors, F. Wenner, J. Res. Natl. Bur. Stand. (U.S.), 25

Research Paper RP1323 (Aug. 1940).

Training Programs

None.

Future Directions

Effort is being put forth to develop techniques to permit companies

to run a reverse MAP - i.e., to minimize NBS involvement in data

processing and, if posible, permit companies to use their own transport

standards and NBS calibration services as the basis for quality-control

in the resistance area. A large effort is being made to reduce

uncertainties and turnaround time via automation. The system for

calibrating Thomas- type resistors was automated recently, resulting in a three-fold improvement in precision. The same techniques are being

applied to the calibration of 0.1 to 100 ohm standards. A capacitance

discharge system for calibrating resistors above a terahom will be

completed in the next year. The development of an unbalanced bridge

technique for the calibration of resistors in the range from 10 ohms to one megohm will take place over the next two years. Calibrations of

resistors with greater magnitudes than one teraohm will be reinstated

upon completion of the new automated capacitance discharge system.

Another major activity is that of establishing a resistance

standard based on atomic physics via the quantized Hall effect discovered by von Klitzing in 1980. This activity has three aspects: the

characterization of the effect itself as manifested in MOSFET's and

gallium arsenide heterostructures, the development of improved methods

to measure the resistances involved at very low power levels, and the

improvement of scaling techniques to link the Hall resistances (6453.2

and 12906.4 ohms) to the legal unit, maintained at the one-ohm level.

It is expected that in three to five years this effect will be used both

nationally and internationally as the preferred method of maintaining

the ohm, freeing this area of resistance metrology from dependence on artifact standards and their material-linked properties.

Upon completion of the automation projects and the adoption of a quantized Hall effect primary resistance standard, efforts will be

redirected to the areas of improving both transport and working

resistance standards; developing seminars, courses, and publications to

teach resistance measurement technology to the metrology community; and

address techniques for making resistance measurements under adverse

conditions.

40
Planned documentation with target dates are as follows:

Compendium of resistance measurement Dec. 1984

papers jointly with NCSL and IEEE.

Operational and quality control June 1985

procedures document.

Error analysis document. June 1985

Contact Person at NBS

Norman Belecki

Electricity Division

301-921-2715

41
PRECISION APPARATUS (3.2)

Description of Services

This service covers Hamon resistance transfer devices, and inductive voltage dividers at 400, 1000, 10000 Hz and Silsbee-type primary

voltage ratio standards from 1.5 to 1500 volts dc. Hamon devices are calibrated by comparing their series and parallel -mode resistances with

those of NBS-constructed devices on a one-to-one basis. This tests the

parallel to series transfiguration error of the device. Inductive

voltage dividers are calibrated by comparison with a two-stage, threedecade transformer of known ratios. Silsbee standards are done by

one-to-one comparison with a primary voltbox, which is self-calibrated

by design.

Documentation

American National Standard for Decade Transformer Dividers (Voltage

Type), ANSI C100, 1-1972 (Jan. 1972).

Instructions for the Use of the NBS Reference Inductive Divider, Wilbur

C. Sze, National Bureau of Standards, Unpublished (1970).

Two-Stage, Guarded Inductive Voltage Divider for Use at 100 kHz, D. H. Hamon and T. L. Zaf, ISA Transactions, 9, 3 (1970).

Comparator for Calibration of Inductive Voltage Dividers from 1 to 10

kHz, W. C. Sze, ISA Transactions, 6, 4 (1967).

Training Programs

None.

Future Directions

There will be little activity other than the maintenance of the

calibration facility, or spin-offs from the development work in the

impendance area.

Contact Person at NBS

Norman Belecki

Electricity Division

301-921-2715

42
IMPEDANCE MEASUREMENTS (3.3)

Description of Services

This service covers the calibrations of standard capacitors and

inductors in the audio-frequency range. Capacitors of the air (0.001 to

1000 pF), fused-silica (10 and 100 pF), and silvered-mica (1 to 1000 pF)

type can be measured at frequencies between 66-2/3 and 10,000 Hz.

Inductors having nominal values between 0.01 mH and 10 H can be measured

at the same frequencies.

Documentation

Testing to Quantify the Effects of Handling of Gas Dielectric Standard

Capacitors, C. R. Levy, Natl. Bur. Stand. (U.S.), Tech. Note 1161

(1982).

Transportable 1000 pF Standard, G. M. Free and J. J. Morrow, Natl. Bur.

Stand. (U.S.), Tech. Note 1162 (1982).

New Measurements of the Absolute Farad and Ohm, R. D. Cutkosky, IEEE

Trans. Instrum. Meas. , IM-23, No. 4, 305 (Dec. 1974).

Applications of Coaxial Chokes to A-C Bridge Circuits, D. N. Homan, J. Res. Natl. Bur. Stand. (U.S.), 72C, No. 2 (June 1968).

Improved Ten-Picofarad Fused Silica Dielectic Capacitor, R. D. Cutkosky

and H. L. Lee, J. Res. Natl. Bur. Stand. (U.S.), 69C, No. 3 (Sept.

1965).

Calibration of Inductance Standards in the Maxwell -Wei n Bridge Circuit,

T. L. Zapf, J. Res. Natl. Bur. Stand. (U.S.), 65C, No. 3 (Sept. 1961).

Capacitance Bridge — NBS Type 2, R. D. Cutkosky, Natl. Bur. Stand.

(U.S.), Report 7103 (Mar. 1961).

Training Programs

None.

Future Directions

The major efforts in this area are directed to the improvement of

the quality of calibrations by replacing worn out or obsolete apparatus

and by improving quality-control procedures. In particular, a replacement for the Maxwell -Wien bridge used to calibrate standard

inductors has been developed and is under test. The replacement bridge

will cover a broader frequency range, up to 100 kHz, than the present

bridge, and can be used for ac resistance measurements if proper

standards are developed. Replacement of the Type II capacitance bridge

is planned also. An automated substitute bridge is expected to be

developed in about three to four years' time. Improved quality-control

techniques to be instituted will inclue a more effective system of check

standards and a scheme for comparing the ratios in the Type II bridge

43
with those of the transformer used as the standard in the inductive

voltage divider set-up. Efforts are also underway to resume the

currently suspended capacitance MAP with new transport standards for

1 pF at frequencies from 400 to 1000 Hz.

Contact Person at NBS

Norman Belecki

Electricity Division

301-921-2715

44
VOLTAGE MEASUREMENTS (3.4)

Description of Services

This service provides for the calibration of standards of direct

voltage (saturated and unsaturated standards cells at 1.02 V and Zener

diode-based electronic standards from 6.5 to 10 V) and voltage MAP

services. The volt is maintained by monitoring the emf's of a group of

six saturated standard cells in an oven on a monthly basis using the ac Josephson effect and a specialized measurement system to perform the

required scaling (from ~ 10 mV to 1.02 V). Customer cells are calibrated

by comparing their emf's with those of working groups of standard cells

on a one-to-one basis using low-level potentiometers and nanovoltmeters.

Electronic standards with output voltages in the ranges from six to ten

volts are measured relative to a group of standard cells using an automated system.

Documentation

Volt Transfer Program Instructions, revised in 1983, unpublished.

A High-Resolution Prototype System for Automatic Measurement of Standard

Cell Voltages, D. W. Braudaway and R. E. Kleinmann, IEEE Trans. Instrum.

Meas., IM-23, No. 4, 282-286 (Dec. 1974).

Volt Maintenance at NBS via 2e/h: A New Definition of the NBS Volt, B.

F. Field, T. F. Finnegan, and J. Toots, Metrologia, 9, 155-166 (1973).

Designs for Surveillance of the Volt Maintained by a Small Group of

Saturated Standard Cells, W. G. Eicke and J. M. Cameron, Natl. Bur.

Stand. (U.S.), Tech. Note 430 (Oct. 1967).

Standard Cells - Their Construction, Maintenance and Characteristics, W.

J. Hamer, Natl. Bur. Stand. (U.S.. ), Monogr. 84 (Jan. 1965).

Training Programs

A week-long seminar on MAP techniques for voltage measurements is

being held twice yearly at various locations. Statistical concepts,

quality-control techniques, and standard cell metrology principles are presented.

Future Directions

The major current activity is that of automating the standard cell

calibration facility. The measurements on transport standards required

for the MAP are made using an automated system. All other measurements

are made manually. Recent work has shown the feasibility of using

high-accuracy digital multimeters as standard cell comparators with

resolution of ten nanovolts or better. This resolution readily suffices

for calibration of nearly all standard cell enclosures. Moreover, the use of such instruments precludes accidental damage to the cells because

of the high input impendance of the meters. These multimeters are

45
easily operated under the control of desktop computers under the control

of the IEEE 488 instrumentation bus. Preliminary design for such

measurement systems has been completed and a prototype is being built

for evaluation. A second major effort is the development of a MAP

transfer service at the ten-volt level using Zener-diode based standards.

A system has been constructed to make measurements at the 0.2 ppm level

of precision to evaluate components. A suitable transport standard is

likely to be developed by October 1985 and testing will follow. Upon

completion of the automation work and the institution of MAP services at

the ten-volt level, attention will be focused on providing support for

voltage levels up to 1000 volts dc. Scaling apparatus developed to

support volt- ratio MAP activities last decade will be rejuvinated to

provide the basis for development of a MAP service for high voltages

needed to support new, high-accuracy 7 and 8 digit multimeters.

Transport standards capable of measuring or supplying such voltages with

accuracy of 5 ppm or better will need to be developed. Measurement

techniques to determine the effects of noise, faulty grounds, common- mode signals, etc., will be needed. Techniques to determine optimum

test point sets for various types of meters will be studied to minimize

the effort required to characterize a multimeter or measuring system.

Planned documentation includes a manual on voltage operating and

quality control procedures (Sept. 1984) and an overview publication on voltage measurements (Jan. 1985).

Contact Person at MBS

Norman Belecki

Electricity Division

301-921-2715
ELECTRICAL INSTRUMENTS (3.5)

Description of Services

This service covers the calibration of thermal voltage and current

converters, ac shunts, and primary thermo-elements used to make measurements of alternating current and voltage in terms of direct current

standards of voltage and resistance. These are carefully compared with

similar NBS devices which have been calibrated using the NBS primary set

of multi junction thermo-elements as a defining standard. The frequency

range covered is from 2 Hz to 1 MHz, with higher frequencies being

covered by the Electromagnetic Technology Division in Boulder. Voltages

as high as 1000 volts are covered, but only up to 50 kHz.

Documentation

The Practical Uses of AC-DC Transfer Instruments, E. S. Williams, Natl.

Bur. Stand. (U.S.), Tech. Note 1166 (Nov. 1982).

A Thermoelement Comparator for Automatic AC-DC Difference Measurements,

E. S. Williams, IEEE Trans. Instrum. Meas. IM-29, No. 4, 405 (Dec.

1980).

An Investigation of Multi junction Thermal Converters, F. L. Hermach and

D. R. Flach, IEEE Trans. Instrum. Meas. , IM-25, No. 4, 524 (Dec. 1976).

Thermal Voltage Converters and Comparators for Accurate AC Voltage

Measurements, E. S. Williams, J. Res. Natl. Bur. Stand. (U.S.), 75C

(Dec. 1971).

Training Programs

None.

Future Directions

The major activities in the electrical instruments area are those

of reevaluating the primary, secondary, and working standards; investigating the properties of new solid-state thermo-elements, and automating

the calibration set-ups. The first is nearly complete. Data will be

collected over the next year to permit a statistical evaluation of

the results. A new, automated system has been constructed to compare

solid-state with conventional thermal converters in order to measure

their frequency response more accurately. The evaluation of these

devices is expected to take a year or more. A new system for automated

calibrations is under consideration. Several measurement approaches are being looked at and the development of a practical system will be

complete in a year to eighteen months. This will relieve the backlog of

calibrations experienced in this area for the past three years.

There are two major areas which will be addressed in the future.

The first is that of the development of a MAP-type service for alternating

47
current and voltage measurements. Currently available equipment could

be used as the basis for a MAP service for ac-dc difference

measurements. While this is a required constituent of the process of

making measurements of alternating quantities, it is by no means the

only constituent. It is quite possible for a laboratory to make good

ac-dc difference measurements but have serious problems with

measurements of current and voltage. Accordingly, transport standards

which are either sources or measurement systems need to be devised and

checked before it is possible to say anything about a lab's capability

in this area. The second major area is that of developing the next

generation of ac-dc standards and comparison apparatus. The present

primary standards, multi junction thermo-elements, are limited in both

signal and frequency range. New technology will be explored for the

feasibility of producing standards at the part in ten-million level of

accuracy.

Contact Person at NBS

Norman Belecki

Electricity Division

301- 921-2715

48
DC- AC VOLTAGE, CURRENT, AND POWER MEASUREMENTS (3.6)

Description of Services

Calibrations are made on devices that are of high quality for use

as reference standards. These include voltage and current transformers,

voltage dividers, high voltage resistors and capacitors, and watthour

meters.

NBS provides services for the measurement of complex voltage ratios

(magnitude and phase angle) of transformers for primary voltages up to

150 kV and for secondary voltages above 50 V. Results of these tests

are reported with an uncertainty of ± 0.03% for ratio and ±0.3 mrad for

phase angle. Calibrations of these voltage transformers are done

routinely only at 60 Hz. Measurements are made with one side of both

the primary and secondary windings connected to ground. Current transformers, with a rated secondary current of 5 A, can be calibrated at

0.5, 1, 2, 3, 4, or 5 A. These tests are carried out at 50, 60, and 400

Hz. For measurements of 50 or 60 Hz, the results are generally reported

with an uncertainty of ± 0.01% in ratio and ± 100 prad in phase angle.

For measurements at 400 Hz, the reported uncertainty is ± 0.03% in ratio

and ± 300 prad in phase angle.

A calibration service is maintained at NBS to specify the dc

voltage ratio of resistive dividers. This calibration service is

available for applied voltages from 10 to 150 kV. The calibrations are performed with a measurement system which has an uncertainty of ± 0.01%

of the voltage ratio. To assure adequate sensitivity at the lowest

applied voltage levels, calibrations are performed only on dividers with

ratios of 100,000:1 or smaller. The calibration service is also

restricted to dividers with a low- resistance element of 10,000 ohms or

less.

AC high-voltage dividers are calibrated at 60 Hz for applied

voltages between 10 and 100 kV rms. There are high voltage dividers

which perform satisfactorily as standards under dc voltages but which

cannot be considered standards when excited by 60-Hz voltages. The

design of an ac divider requires special care beyond that of a dc

divider. In particular, ac dividers designed to be used as transfer

standards may have to be equipped with external shielding to minimize

the effects of capacitive coupling to surrounding objects. Calibrations

are performed with a measurement system which has an uncertainty of

± 0.05% in the determination of the ratio and ±0.5 mi Hi radian in the

determination of the phase angle. The calibration of dividers used to

measure the high voltage in diagnostic x-ray units consists of three

measurements. These are the measurements of the variation of the ratio

with a change in the frequency of the applied voltage in the frequency

range from dc to 10,000 Hz; a determination of the ratio under direct

voltage at 25 kV; and a measurement of any voltage induced variation of

the ratio in the voltage range from 20 to 70 kVp. If the device under

test is designed to operate continuously under full rated voltage, this

last test is done at three dc voltages between 20 and 70 kV. If it

cannot operate continuously, a preselected number of half cycles of

60-Hz voltage ranging in magnitude from 20 to 70 kVp are applied. These

49
calibrations are performed with an uncertainty of ± 0.1% of the

indicated value of the dc ratio at 25 kV, an uncertainty of ± 1% of the

indicated value of the frequency dependence and it is generally reported

that the ratio varied by less than ± 1% as the applied voltage is varied

over the full range. Ratios of resistive, capacitive, or mixed-vol tage

dividers are determined under pulsed high-voltage conditions.

Determinations employ specially designed pulse dividers and calibrated

Kerr cells as reference standards. A variety of pulses may be applied

to simulate the conditions under which the divider will be used.

Calibrations are made at selected voltage intervals from 20 to 300 kV as requested and up to 500 kV with certain pulse shapes. The typical

uncertainty is i 3% of the voltage ratio.

A calibration service is maintained for resistors designed for dc

high-voltage applications. This service is designed for nearly coronafree resistors designed for dc operation between 10 and 150 kV. A

calibration service is also maintained for capacitors designed for 60-Hz

operations, especially at voltages above 100 V. Typical uncertainties

for a calibration are ± 100 ppm of the capacitance, and ± 1% of the

dissipation factor ± 1 x 10~5. Routine calibrations are limited to

devices with a dissipation factor of 0.011 or smaller and which are operated at sufficient voltage that at least 40 pA pass through the

device under test.

Calibration services are available for portable watthour meters of

the rotating and electronic types. The test conditions must be

specified by the customer. These include the current (0.5 to 50 A),

voltage (± 10 V around 120, 240, and 480 V), 50 or 60 Hz, and power

factor of 1.0, 0.5 leading, or 0.5 lagging. The duration of a calibration run is about 100 seconds for a power factor of 1.0 and about 200

seconds for a power factor of 0.5. The reported values of the

percentage registration generally have uncertainties of ± 0.05% of the

indicated value. A Measurement Assurance Program for electric energy is

also available to evaluate energy measuring equipment. An NBS-owned,

transport standard, watthour meter is shipped to the customer and a tie

is made to the U.S. national energy unit without the downtime encountered

when the customer's standards are shipped to and calibrated by NBS. In

addition, and more important to those who calibrate standard watthour

meters, the MAP standard can be used by customers to evaluate their

measurement process in a convenient and cost effective way.

Documentation

A Wide Range High-Voltage Capacitance Bridge With One ppm Accuracy, 0.

Petersons and W. E. Anderson, IEEE Trans. Instrum. Meas. , IM-24, No. 4,

336-344 (Dec. 1975).

An Electronic Ratio Error Set for Current Transformer Calibrations, R.

L. Kahler, IEEE Trans. Instrum. Meas., IM-28, No. 2, 162-164 (June

1979).

A Wide Range Current Comparator System for Calibrating Current

Transformers, T. M. Souders, IEEE Trans. Power Appar. Syst. , PAS-90, No.

1, 318-324 (Jan. -Feb. 1971).

50
Wide-Band Two-Stage Current Transformers of High Accuracy, T. M. Souders, IEEE Trans. Instrum. Meas., IM-21, No. 4, 340-345 (Nov. 1972).

X-CAL - A Calibration System for Electrical Measurement Devices Used

With Diagnostic X-Ray Units, R. H. McKnight and R. E. Hebner, Natl. Bur.

Stand. (U.S.), NBSIR 79-2072, 74 pages (June 1980).

Evaluation of a Multimegavolt Impulse Measurement System, R. E. Hebner,

D. L. Hillhouse, and R. A. Bullock, Natl. Bur. Stand. (U.S.), NBSIR

79-1933, 97 pages (Nov. 1979).

Calibration of High-Voltage Pulse Measurement Systems Based on the Kerr

Effect, Natl. Bur. Stand. (U.S.), NBSIR 77-1317, 33 pages (Sept. 1977).

Special Shielded Resistor for High-Voltage Measurements, J. H. Park, J. Res. Natl. Bur. Stand. (U.S.), 66C, No. 1, 19-24 (Jan. -Mar. 1962).

A Calibration Service for Wattmeters and Watthour Meters, J. D. Ramboz

and R. C. McAuliff, Natl. Bur. Stand. (U.S.), Tech. Note 1179, 111 pages

(July 1983).

A Measurement Assurance Program for Electric Energy, N. M. Oldham, Natl.

Bur. Stand. (U.S.), Tech. Note 930, 17 pages (Sept. 1976).

Sampling Techniques for Electric Power Measurement, R. S. Turgel , Natl.

Bur. Stand. (U.S.), Tech. Note 870, 31 pages (June 1975).

Transfer of the Ki lowatthour, S. R. Houghton, IEEE Trans. Power Appar.

Syst. , PAS-94, No. 4, 1232-1240 (July-Aug. 1975).

A Current Comparator System to Establish the Unit of Electrical Energy

at 60 Hz, K. J. Lentner, IEEE Trans. Instrum. Meas. , IM-23, No. 4,

334-336 (Dec. 1974).

Training Programs

There is no formal schedule of educational seminars, but over the

last few years NBS has sponsored one or two seminars per year on selected topics in electrical measurements. Potential participants can have their names added to the mailing lists for these seminars by

contacting the person listed at the end of this section.

Future Directions

NBS will develop a capability to evaluate shunts and current

transformers used to measure welding currents. This application

requires the measurement of current pulses with amplitudes up to 100 kA

and durations of tens to hundreds of milliseconds. Development of a bridge for calibrating shunts down to 0.1 mQ and up to frequencies of

100 kHz is progressing slowly with the present funding level. Long

range plans also include support of dc current measurements from 5 to

2000 A as a step toward developing support for dc revenue metering in

high voltage dc systems.

51
NBS 1 present capabilities for power and energy calibration are restricted to power frequencies, 50 to 400 Hz, with a routine

uncertainty of ± 0.05%. Under special conditions, we are able to

achieve uncertainties in the range ± 0.01 to ± 0.02%. These capabilities

are for unity and 0.5 power factor, but no measurements at zero power

factor. Present plans are to gradually upgrade this facility during the

next 5 years. The goal is to develop a largely automated facility

having the following characteristics:

Frequency : 40 Hz to 10 kHz Waveforms: sinusoidal and

distorted

Voltage : 10 to 240 V Quantities: power, energy, VAR,

power factor, voltage,

and current

Current :

Power Factor :

10 mA to 10 A

al 1 , zero to

unity, positive

and negative

Accuracy: ± 0.01% to ± 0.05%

routine, ± 50 ppm special

Contact Person at NBS

Robert E. Hebner, Jr.

Electrosystems Division

301-921-3121

52
WATTMETER AND AC VOLTAGE MEASUREMENTS (3.8)

Description of Services

Calibrations of portable ac-dc wattmeters are provided at voltages

ranging from 110 to 130 V, 220 to 260 V, and 440 to 520 V; at currents

from 0.5 to 50 A; and at frequencies up to 60 Hz. The duration of a test run is about 100 seconds and the reported corrections (in watts)

generally have uncertainties of ± 0.05% of the full scale range. A

calibration service is also available for ac voltage standards and rms voltmeters in the 0.1 to 10 Hz range. The ac voltmeters can be

calibrated at frequencies of 10, 5, 2, 1, 0.5, 0.2, and 0.1 Hz at any

voltage level between 0.5 mV and 7 mV while voltage sources can be

calibrated at any frequency in the 10 to 0.1 Hz range and are usually

tested near the full-scale level of the voltmeter ranges (2, 5, 10, 20,

50 mV, and 0.1, 0.2, 0.5, 1, 2, 5 V).

Documentati on

A Calibration Service for Wattmeters and Watthour Meters, J. D. Ramboz

and R. C. McAuliff, Natl. Bur. Stand. (U.S.), Tech. Note 1179, 111 pages

(July 1983).

An rms Digital Voltmeter/Calibrator for Very-Low Frequencies, H. K. Schoenwetter , IEEE Trans. Instrum. Meas. , IM-27, No. 3, 259-268 (Sept.

1978).

AC Voltage Calibrations for the 0.1 Hz to 10 Hz Frequency Range, H. K. Schoenwetter, Natl. Bur. Stand. (U.S.), Tech. Note 1182, 56 pages (Sept.

1983). (This reference provides a complete description of the

calibration service.)

Training Programs

There is no formal schedule of educational seminars, but over the

last few years NBS has sponsored one or two seminars per year on selected topics in electrical measurements. Potential participants can

have their names added to the mailing lists for these seminars by

contacting the person listed at the end of this section.

Future Directions

A system capable of calibrating alternating voltage sources or voltmeters in the ± 10 ppm accuracy range (1 to 1000 V and up to

100 kHz) is being developed. This system can also characterize the

ac-dc difference of thermal voltage converters. A second more portable

system is being developed for calibrating dc/ac voltmeters in the ± 5/±

50 ppm accuracy range which may ultimately cover frequencies up to 1

MHz. The primary application is calibration of programmable sources and

automated test equipment.

Contact Person at NBS

Robert E. Hebner, Jr.

Electrosystems Division

301-921-3121

53
DATA CONVERTER MEASUREMENTS (3.9)

Description of Services

NBS maintains a calibration service for high resolution (12-18 bit)

analog-to-digi tal (ADC) and digital-to-analog (DAC) converters.

Measurements are made on the linearity, differential linearity, offset,

gain, and equivalent runs of the data converters. To be compatible

with the NBS data converter test set, test units must conform to the

following general specifications:

o Nominal resolution from 12- to 18-bits;

o Conversion rate of at least 10 kHz;

o Binary coding format, including binary sign-magnitude, offset

binary, 2's complement, I's complement, and complemented

versions of these;

o TTL compatibility;

o Voltage ranges of 0-5 V, ± 5 V, 0-10 V, ± 10 V; and

o Maximum error including offset and gain, not to exceed 500

ppm.

In general, it is the customer's responsibility to mount integrated

circuit, hybrid, or modular test converters on suitable test boards,

providing all required trimmer circuits, voltage references, input or output amplifiers, recommended power supply decoupling capacitors, and

connectors for interfacing to the input/output lines. Fully selfcontained converters need only be fitted with the necessary interfacing

connectors.

Documentation

A Calibrated Service Analog-to-Digital and Digi tal-to-Analog Converters,

T. M. Souders, D. R. Flach, and B. A. Bell, Natl. Bur. Stand. (U.S.),

Tech. Note 1145, 66 pages (July 1981). (This reference provides a complete description of the calibration service.)

A 20-Bit + Sign Relay Switched D/A Converter, T. M. Souders and D. R. Flach, Natl. Bur. Stand. (U.S.), Tech. Note 1105, 16 pages (Oct. 1979).

(This describes the reference standard used in the calibration service.)

A Technique for Measuring the Equivalent rms Input Noise of A/D Converters, T. M. Souders and J. A. Lechner, IEEE Trans. Instrum. Meas.

IM-29 (Dec. 1980).

A High-Speed Low-Noise 18-Bit Digi tal-to-Analog Converter, H. K. Schoenwetter , IEEE Trans. Instrum. Meas. , IM-27 (Dec. 1978).

An Automated Test Set for the Dynamic Characterization of A/D

Converters, T. M. Souders, D. R. Flach, and T. C. Wong, IEEE Trans.

Instrum. Meas. , IM-32 (Mar. 1983).

54
Training Programs

There is no formal schedule of educational seminars, but over the

last few years NBS has sponsored one or two seminars per year on selected topics in electrical measurements. Potential participants can have their names added to the mailing lists for these seminars by

contacting the Electrosystems Division at the address given below.

Future Directions

NBS has recently developed the capability to measure the dynamic

response of ADCs to well defined, programmable input voltage

characteristic of typical input signals. Until further analysis of

systematic and random errors of the test procedure is completed and

until additional operating experience is obtained these dynamic

measurements will only be offered as a special test.

Contact Person at NBS

Thomas M. Souders

Electrosystems Division

301- 921-2727

55

ATTENUATION (4.1)

D escription of Services

NBS provides calibration services for attenuation and phase shift

measurement listed below:

Attenuation Measurement of Coaxial Attenuators

(a) Fixed and Variable Attenuators

Coaxial fixed and variable attenuators are measured on the NBS

modified automatic network analyzer (ANA) over the frequency range 0.1

to 18 GHz.

All measurements are made by the substitution method, which

requires that the connectors used be asexual or that the attenuator have

a male connector at one port and a female at the other. If an adapter

is required to comply with the foregoing, it must be supplied with the

attenuator. The combination will be calibrated as one unit.

In addition to measurements performed on the ANA, measurements at a fixed frequency of 30 MHz are available referenced to the NBS waveguide

below cutoff standard at this frequency.

Coaxial attenuators are normally measured in a system having a characteristic impedance of 50 Q. Limits of uncertainty depend upon the

VSWR of the individual attenuator, quality of the attenuator and

connectors, and the magnitude of the attentuation. Typical systematic

uncertainties range from 0.03 to 0.05 dB/10 of attenuation.

(b) Attenuation Measurements at 30 MHz

Incremental attenuation. Incremental attenuation is the change in

attenuation of an adjustable attenuator between a reference setting

(usually zero) and any other setting. The same restraints on system

conditions apply as for attenuation. The term "differential attenuation"

is sometimes applied.

Measurements on waveguide-below-cutoff (piston) attenuators are performed at 30 MHz. These attenuators are normally quite stable and

seldom need recalibration unless damaged or mechanically worn. Since

any laboratory can perform independent checks to determine continuing

repeatability and linearity of attenuation, periodic NBS recalibrations

are not recommended. This recommendation, in part, is also because more damage can be suffered in transit than in daily use. In any measurement,

the maximum power delivered to the test attenuator will not exceed 400

mW. If the attenuator cannot tolerate this power level, some reduction

of measurement range will be required.

Piston attenuators are normally calibrated in a system having a characteristic impedance of 50 Q. Since only measurements of incremental

attenuation are made on this type of attenuator, Type BNC, C, TNC, and

similar connectors are acceptable, but precision connectors are preferred

57
to reduce leakage. Limits of uncertainty depend upon the quality of the

attenuator and connectors, as well as upon the VSWR of the attenuator,

and the magnitude of attenuation. Typical systematic uncertainties

range from 0.003 to 0.005 dB/10 dB of attenuation.

(c) Attenuation Measurements Below 10 MHz

Special tests may be performed over the frequency range 30 kHz to

10 MHz using the voltage ratio measurement technique. These tests are limited to attenuators with GR 874 connectors and to 10 dB maximum.

(d) Standard Transmission Lines

The characteristic impedance, Z

Q

, and the equivalent electrical

length of air-di electric coaxial transmission lines are calculated from

measurements of the physical dimension of the line and estimates of the

electrical conductivity of the line. The physical dimensions are measured with precision air gages.

The electrical parameters vary slightly with frequency because of

the finite conductivity of the material. The calibration report includes

a table of electrical parameters calculated at different frequencies for

a typical value of conductivity. The actual conductivity of the line

material is not determined.

(e) Rectangular Waveguide Variable Attenuators

Variable waveguide (usually rotary vane) attenuators are calibrated

in various frequency bands by the IF-substi tution technique referenced

to 30 MHz, direct rf substitution, or on the NBS modified ANA, as appropriate.

It is suggested that measurements requested be held to a minimum

number of settings at a single band-center frequency, which should be

sufficient to determine the characteristics of the device. It is

further recommended that previously calibrated units not be resubmitted

unless tests performed by the user indicate a shift in values.

The uncertainty is a function of resettabi 1 ity and input VSWR of

the waveguide ports. Devices submitted should be in the best possible

condition to justify calibration and ensure long-term stability of

measured values. Typical systematic uncertainties range from 0.03 to

0.05 dB/10 dB of attenuation.

Documentation

Applications of Waveguide and Circuit Theory to the Development of

Accurate Microwave Measurement Methods and Standards, R. W. Beatty,

Natl. Bur. Stand. (U.S.), Monogr. 137, 218 pages, (Aug. 1973).

Basic Theory of Waveguide Junctions and Introductory Microwave Network

Analysis, D. M. Kearns and R. W. Beatty, Pergamon Press Inti. Series of

Monographs in Electromagnetic Waves, 13, 59-63 (1967).

58
Effects of Connectors and and Adapters on Accurate Attenuation

Measurements at Microwave Frequencies, R. W. Beatty, IEEE Trans.

Instrum., 13, 272-284 (Dec. 1964).

Insertion Loss Concepts, R. W. Beatty, Proc. IEEE, 52(6), 663-671 (June

1964).

Rf Attenuation, D. Russell, Proc. IEEE, 55(6), 942-959 (June 1967).

IEEE Standard 474-1973, Specifications and Test Methods for Fixed and

Variable Attenuators, dc to 40 GHz.

Training Programs

None.

Future Directions

Presently, routine calibrations are provided only for linear,

reciprocal, one-port and two-port networks and then only over limited

frequency and parameter ranges. It is planned to greatly extend the

coverage in the near future providing all S-parameter measurement at

most frequencies from 100 kHz to 100 GHz, and for |S 12 | up to

approximately 60 dB.

Plans call for providing attenuation measurements of special

three-port devices at 1.25 MHz. A measurement system is being developed

to measure the change in the ratio |S21 /S31 | of special stable

two-position three-port devices, sometimes called voltage doublers, at

1.25 MHz.

Contact Person at NBS

Cletus Hoer

Electromagnetic Technology Division

303-497-3705

59
FIELD AND ANTENNA MEASUREMENTS (4.2)

Description of Services

Measurement services are generally available for microwave and

low-directivity antennas from 30 Hz to 75 GHz. Antenna measurements are conducted as special tests owing to the great variability in antenna

design, performance, and use.

Accurate measurement of microwave antenna gain, pattern, and

polarization are generally available from about 750 MHz to about 75 GHz.

Antennas submitted for evaluation should be mechanically and

electrically stable in order to retain a calibration for a significant

length of time. Antennas with either coaxial or waveguide connectors

can be measured; however, if coaxial connectors are employed, they

should be precision connectors to minimize uncertainties due to a lack

of connector repeatability. Extrapolation range measurements offered

primarily for determining the absolute on-axis gain and polarization of

standard gain horns which are, in turn, used as reference standards in

determining the gain and polarization of other antennas by the gain

comparison technique. Above 1 GHz, the accuracies are typically ±0.05

dB/dB for polarization axial ratio measurements. Gain, pattern, and

polarization parameters are calculated from Near-Field Scanning

Measurements in which amplitude and phase measurements are taken over a surface close to the test antenna. The absolute gain can be determined

to within about ± 0.15 dB, the polarization axial ratio to within about

± 0.10 dB/dB, and side lobe levels can be obtained down to -50 or -60 dB.

Non-direction antenna measurements for radiated field strength

measurements are available as indicated in the following table:

Field

Parameter

Type of

Measurement

Faci 1 ity

Frequency

Range

Radiating

Antenna

Source

H(near zone) Wood building 30 Hz - 50 MHz Loop (20 cm)

E(vertical

Open site

(ground screen)

10 kHz - 30 MHz Short monopole

E(vertical

Open site

(ground screen)

30 - 300 MHz X/4 monopole

E(horizontal

Open site 30 - 300 MHz Receivi ng

X/Z dipole

Power density Anechoic chamber 200 - 500 MHz Open-end wave

guide

0.5 - 18 GHz Pyramidal horn

60
Measurement services are also offered for antenna systems, field

strength measurement devices, and both electric (E) and magnetic (H)

field probes and meters.

Documentation

Accurate Measurement of Antenna Gain and Polarization at Reduced

Distances by an Extrapolation Technique, A. C. Newell, R. C. Baird, P.

F. Wacker, IEEE Trans. Antennas Propagat. , AP-27, No. 4, 418-431 (July

1973).

Determination of Both Polarization and Power Gain of Antennas by a Generalized 3-Antenna Measurement Method, A. C. Newell and D. M. Kerns,

Electronics Letters, 7, No. 7, 68-70 (Feb. 1971).

Correction of Near-Field Antenna Measurements Made With an Arbitrary but

Known Measuring Antenna, D. M. Kerns, Electronics Letters, 6, No. 11,

346-347 (May 1970).

New Method of Gain Measurement Using Two Identical Antennas, D. M. Kerns, Electronics Letters, 6, No. 11, 348-349 (May 1970).

Plane-Wave Scattering-Matrix Theory of Antennas and Antenna-Antenna

Interactions: Formulation and Applications, D. M. Kerns, J. Res. Natl.

Bur. Stand. (U.S.), 806 (Math. Sci.), No. 1, 5051 (Jan. -Mar. 1976).

Plane-Wave Scattering-Matrix Theory of Antennas and Antenna-Antenna

Interactions, D. M. Kerns, Natl. Bur. Stand. (U.S.), Monogr. 162 (June

1981).

Upper-Bound Errors in Far- Field Antenna Parameters Determined from

Planar Near-Field Measurements, A. D. Yaghjian, Natl. Bur. Stand.

(U.S.), Tech. Note 667 (Oct. 1975).

The Near-Zone Magnetic Field of a Small Circular Loop Antenna, F. M. Greene, J. Res. Natl. Bur. Stand. (U.S.), 71C (Eng. and Instr.), No. 4

(Oct. -Dec. 1967).

Calibration Principles and Procedures for Field Strength Meters (30 Hz

to 1 GHz), H. E. Taggart and J. L. Workman, Natl. Bur. Stand. (U.S.),

Tech. Note 370 (Mar. 1969).

NBS Field Strength Standards and Measurements (30 MHz to 1000 MHz), F. M. Greene, Proc. IEEE, 55, 970-981 (June 1967).

Field Strength Above 1 GHz: Measurement Procedures for Standard

Antennas, R. R. Bowman, Proc. IEEE, 55, 981-990 (June 1967).

Electromagnetic Waves and Radiating Systems, E. C. Jordan, Prentice-Hall

Inc. (1950).

Antennas Theory and Practice, S. A. Schelkunoff and H. T. Fritz, John

Wiley and Sons, Inc. (1952).

61
Generation of Standard EM Field Using TEM Transmission Cells, M. L. Crawford, IEEE Trans. Electromag. Compat. , EMC-16, No. 4, 189-195 (Nov.

1974).

Design and Calibration of the NBS Isotropic Electric Field Monitor

(EFM-5) , 0.2-1000 MHz, E. B. Larsen and F. X. Ries, Natl. Bur. Stand.

(U.S.), Tech. Note 1033 (Mar. 1981).

Training Programs

A variety of consultation and advisory services are available upon

request. Included are cooperative measurement programs, wherein a customer may bring an item to NBS for measurement and actually

participate in the measurements in order to become familiar with the

measurement methods and assist in the analysis of the results. This is

a useful approach when one is attempting to establish a new measurement

capability that is related to, or based upon, NBS measurement

techniques.

Future Directions

Work is in progress to enable NBS to respond to the measurement

problems associated with electromagnetic interference and radiation

hazards.

Contact Person at NBS

Norris S. Nahman

Electromagnetic Fields Division

303-497-5167

or

Ramon C. Baird

Electromagnetic Fields Division

303-497-3301

62
IMPEDANCE OR ADMITTANCE (4.3)

Description of Services

Calibration services provided in this category are for passive

devices over the frequency range from 10 kHz to 95 GHz. Highest

accuracy is obtained only for standards equipped with precision coaxial

connectors or waveguide flanges. Standards submitted for calibration

should be in good repair and, except for very minor cleaning of connector

surfaces, should require no precalibration maintenance. NBS does not

provide repair services so that items received which require maintenance

will be returned to the sender and a handling fee will be charged.

o Capacitance, Two-Terminal, Low-Loss

In the frequency range from 30 kHz to 250 MHz, capacitance calibrations to a minimum uncertainty of ± 0.1 percent are available from 1 pF

to 1 pF depending upon frequency. The upper capacitance limit for

calibration decreases as the frequency increases and is 50 pF at 5 MHz

and above. At 1 MHz a special high accuracy service is available for

capacitors with nominal values of 50, 100, 200, 500, and 1000 pF provided

they are equipped with 14 mm coaxial connectors.

A technique for extrapolating the 1 kHz values of capacitance

standards to high frequencies is described by R. N. Jones. This

reference describes a technique for obtaining a high frequency value of

a capacitor equipped with an unshielded (banana plug) connector. The

measurement technique yields effective capacitance values at high

frequencies using the capacitance value at 1 kHz and the residual series

inductance. The same technique, with some modifications, is usable for

three- terminal and four-terminal pair capacitors. It is emphasized that

these extrapolation procedures are only usable for air dielectric

capacitors or capacitors with insulating materials whose dielectric

constant does not change with frequency.

0 Capacitance, Three-Terminal, Low-Loss

Services are available at 100 kHz and 1 MHz for capacitors having

values of 10, 100, and 1000 pF. Calibration uncertainty is typically

± 0.02 percent for all frequencies and values except for 1000 pF at

1 MHz where the uncertainty is nominally ± 0.04 percent.

Fixed value reference standards are maintained by NBS for values of

10, 100, and 1000 pF. High quality three-terminal air dielectric

capacitance standards should have low residual series inductance (<0.1 pH).

This being the case, it may be assumed that to an accuracy of ± 0.10

percent, the capacitances of standards of 1 pF or less with air dielectric

is the same at 1 MHz as it is at 1 kHz. Thus, it is unnecessary to have

capacitors smaller than 10 pF calibrated at 1 MHz.

o Inductors, Two-Terminal, High-Q

In the frequency range from 10 kHz to 250 MHz, inductance calibrations

to a minimum uncertainty of ± 0.1 percent are available from 0.01 pH to

63
1 H. The upper inductance limit for calibration decreases as the

frequency increases and is 1 pH at 250 MHz. Service is available only

for aircore inductors or inductors whose value is independent of

current.

o Resistors, Two-Terminal, Low-Q

In the frequency range from 10 kHz to 250 MHz resistance calibrations to a minimum uncertainty of ± 0.1 percent are available from 0.1 Q

to 10 MQ. At higher frequencies the upper limit for resistance decreases

and is 20 kQ at 250 MHz. Calibration services for resistors less than

20 kfi are not available at frequencies above 2 MHz.

o Q- Standards

Standards for Q-measurements are maintained at NBS. These are high-Q inductors equipped with banana plug connectors at a spacing of 1

inch on centers. These standards have inductance values of 0.25, 2.5,

25, 250, 2500, and 25,000 pH, and effective Q- values from 100 to

approximately 600. These serve as working standards for calibration of

Q-standards of a similar type. Calibration frequencies range from

50 kHz to 45 MHz. Provisions are made for calibrating each Q-standard

at three frequencies; however, adequate assurance of stability is

usually provided by recalibrating only at the center frequency.

o Coaxial Terminations, Reflection Coefficient

Services are available for complex impedance, reflection coefficient,

and voltage standing wave ratio (VSWR). Measurements on coaxial devices

in the frequency range 0.1 to 18 GHz are made on the NBS modified

Automatic Network Analyzer (ANA). The calibration services usually

apply to determining the reflection coefficient or VSWR of standard

terminations and mismatches.

o Waveguide Terminations, Reflection Coefficient

Waveguide terminations are measured in a reflectometer system

relative to a quarter-guide wavelength short circuit and a precision

transmission line. Some measurements in waveguide bands below 18 GHz can be performed on the NBS modified Automatic Network Analyzer (ANA)

while all of those above 18 GHz are performed on manual fixed-frequency

systems. Waveguide terminations are usually quite stable and need not

be resubmitted unless tests performed by the user indicate a shift in

val ues.

All calibrations are performed under typical ambient laboratory

conditions of 23 °C, and an atmospheric pressure of approximately

8.4 ± 0.2 x 104 Pa at Boulder, Colorado. Services at ambient conditions

outside these limits are not provided. Also, the power applied to any

device being calibrated does not exceed 1 W.

64
Documentati on

Lumped Parameter

The Measurement of Lumped Parameter Impedance: A Metrology Guide, R. N. Jones, Natl. Bur. Stand. (U.S.), Monogr. 141, 211 pages (June 1974).

Impedance of Lumped Circuits, L. E. Huntley, R. N. Jones, Proc. IEEE,

55(6), 900-911 (June 1967).

A Technique for Extrapolating the 1 kc Values of Secondary Capacitance

Standards to Higher Frequencies, R. N. Jones, Natl. Bur. Stand. (U.S.),

Tech. Note 201, 15 pages (Nov. 1963).

A Precision High Frequency Calibration Facility for Coaxial Capacitance

Standards, R. N. Jones and J. E. Huntley, Natl. Bur. Stand. (U.S.),

Tech. Note 386, 27 pages (Mar. 1970).

Evaluation of Three-Terminal and Four-Terminal Pair Capacitors at High

Frequencies, R. N. Jones, Natl. Bur. Stand. (U.S.), Tech. Note 1024, 15

pages (Sept. 1980).

Standards for the Calibration of Q-Meters, 50 kHz to 45 MHz, R. N. Jones, J. Res. Natl. Bur. Stand. (U.S.), 58C (Eng. and Instr.), 4,

243-248 (Oct. -Dec. 1964).

Coaxi al

An NBS Developed Automatic Network Analyzer, W. Little, et al., Conference

on Precision Electromagnetic Measurements, June 28 - July 1, 1976,

Boulder, Colorado, Digest, p. 130-133.

Waveguide

A Guide to the Use of the Modified Ref lectometer Technique of VSWR

Measurement, W. J. Anson, J. Res. Natl. Bur. Stand. (U.S.), 65C (Eng.

and Instr.), 4, 217-223 (Oct. -Dec. 1961). (The measurement technique

utilized in reflection measurements is described in this paper.)

Millimeter Attenuation and Reflection Coefficient Measurement System, B. C. Yates and W. Larson, Natl. Bur. Stand. (U.S.), Tech. Note 619 (1972).

Training Programs

No training programs currently available.

Future Plans

The introduction of automatic digital impedance and admittance

meters has produced many requests concerning methods and standards for

calibrating them. It is evident that instruments of this type will

eventually replace the traditionally manually balanced impedance bridges

because in addition to speed and versatility, they have demonstrated

65
very good accuracy capabilities. At this time no calibration services

are available either for the meters themselves or for any standards

specifically designed for use with them. However, work directed to this

problem has been initiated with some success in the calibration of those

types having the four- terminal -pair type interface for the connection of

the unknown impedance. A generalized calibration procedure has been

successfully demonstrated wherein the instrument together with an adaptor to a two-terminal (one-port) connector can be evaluated as an integrated measurement system. Correction factors are determined which

will correct the displayed readings to be in agreement with preselected

two- terminal calibration standards. Plans are to pursue this technique

to a point where it can be made available to the measurement community.

Publication of an NBS Technical Note and perhaps the offering of a training seminar are under consideration.

NBS plans to transfer all coaxial, most waveguide, and some lumped

circuit impedance measurements to dual six-port ANAs as they are completed.

Contact Person at NBS

Cletus Hoer

Electromagnetic Technology Division

303- 497-3705

66
LASER POWER AND ENERGY (4.4)

Description of Services

The laser power and energy measurement services include several

Measurement Assurance Programs (MAPs). These MAPs are implemented by

means of transfer standards which have been evaluated and characterized

relative to the national standards (three types of isoperibol type

calorimeters). One of these transfer standards, evaluated for the

specific wavelength and power (energy) range of laser radiation, is

forwarded to each MAP participant twice per year. The participant is

asked to calibrate the transfer standard in accordance with his normal

procedures, or in accordance with procedures sent with the instrument.

The data is then sent to NBS where an analysis is performed. The range

of wavelengths and powers are as follows:

514.5 nm 632.8 nm 632.8 nm 647.1 nm 1.06 pm

1.06 pm

10.6 pm

10 to 660 mW

1 mW

30 and 100 pW

10 to 200 mW

10 mW to 1 W

(Q- switched) 100 mJ to 10 J

5 to 50 W

The uncertainty of these calibrations is about 1 to 5 percent at

the 99 percent level of confidence depending on the power (or energy)

and wavelength at which the calibration is performed.

The laser power and energy measurement services also include a limited number of calibrations of laser power and energy meters. These

calibrations are carried out as special test calibrations in which

customer-owned instruments are sent to NBS for measurement. These

special tests include services to measure 1.064-pm laser pulses from

10-8 to 10”4 watts peak power and 10~16 to 10-11 joules and 10.6-pm

nanosecond pulses using a TEA laser in the 0.1- joule energy range.

Documentati on

An NBS Measurement Assurance Program, A. A. Sanders and A. R. Cook,

Proc. 1976 Electro-Optics Laser Conf.

Theory of Isoperibol Calorimetry for Laser Power and Energy Measurement,

E. D. West and K. L. Churney, J. Appl. Phys. , 41(6), 2705-2712 (May

1970).

A Reference Calorimeter for Laser Energy Measurement, E. D. West, W. E. Case, A. L. Rasmussen, and L. B. Schmidt, J. Res. Natl. Bur. Stand.

(U.S.), 76A (1), 13-26 (Jan. -Feb. 1972).

Data Analysis for Isoperibol Laser Calorimetry, E. D. West, Natl. Bur.

Stand. (U.S.), Tech. Note 396 (Feb. 1971).

The Theory of the Optical Wedge Beam Splitter, Y. Beers, Natl. Bur.

Stand. (U.S.), Monogr. 146 (Oct. 1974).

67
Precision Beam Splitters for CO Lasers, D. Franzen, Applied Optics, 14,

547 (Mar. 1975).

Quality Assurance Program for the NBS C, K, and Q Laser Calibration

Systems, W. Case, Natl. Bur. Stand. (U.S.), NBSIR 79-1619 (Aug. 1979).

Measurement Procedures for the Optical Beam Splitter Attenuation Device

BA-1, B. Danielson, Natl. Bur. Stand. (U.S.), NBSIR 77-858 (May 1977).

Absolute Reference Calorimeter for Measuring High Power Laser Pulses, D.

L. Franzen and L. B. Schmidt, Appl. Opt., 15, 3115 (Dec. 1976).

Spectral -Absorptance Measurements for Laser Calorimetry, E. D. West and

L. B. Schmidt, J. Opt. Soc. Amer. , 65(5) (May 1975).

A System for Calibrating Laser Power Meters for the Range 5-1000 W, E. D. West and L. B. Schmidt, Natl. Bur. Stand. (U.S.), Tech. Note 685 (May

1977).

Evaluating the Inequivalence and Computational Simplification for the

NBS Laser Energy Standards, E. G. Johnson, Appl. Opt., 16, 2315 (Aug.

1977).

Precision Measurement and Calibration, H. Ku, Natl. Bur. Stand. (U.S.),

Spec. Publ . 300 (Feb. 1969).

Documentation of the NBS C, K, and Q Laser Calibration Systems, W. E. Case, Natl. Bur. Stand. (U.S.), NBSIR 82-1676 (Sept. 1982).

A System for Measuring the Characteristics of High Peak Power Detectors

of Pulsed CO Radiation, P. A. Simpson, Natl. Bur. Stand. (U.S.), Tech.

Note 1023 (Sept. 1980).

A System for Measuring Energy and Peak Power of Low-Level 1.064-pm Laser

Pulses, A. A. Sanders and A. L. Rasmussen, Natl. Bur. Stand. (ll.S.),

Tech. Note 1058 (Oct. 1982).

Training Programs

None.

Future Directions

Expand the C series calibration system to include laser power

measurements at several wavelengths in the range 0.8 to 0.9 pm and at

1.3 pm and the K series MAP program to include laser power measurements

up to 300 watts.

Contact Person at NBS

William E. Case

Electromagnetic Technology Division

303-497-3741

68
NOISE TEMPERATURE MEASUREMENTS (4.6)

Description of Services

Calibration or special test services for the measurement of noise sources (generators) are offered in limited frequency coverage from 30

MHz to 94 GHz; the type of service offered being determined by the

frequency. In some frequency regions only spot frequency measurements

are available while in others measurements are available over a band.

Noise temperature measurements are available on single-port, coaxial,

and rectangular waveguide noise sources under conditions of continuous,

unmodulated operation. Precision coaxial connectors or clean, smooth,

and flat waveguide flanges are required. Complete operating instructions

and special electronic connectors should be supplied, and pertinent

operating conditions (voltages, circuits, etc.) specified for the noise

source to be measured. The limits of uncertainty vary with noise

temperature, reflection coefficient, and source and connector stability,

but typically lie between 1% and 3% of the noise temperature.

Documentation

Noise Standards, Measurements, and Receiver Noise Definitions, C. K. S. Miller, W. C. Daywitt, and M. G. Arthur, IEEE Proc. , 55, No. 6, 865-877

(June 1967). (This reference describes noise standards, basic principles

of noise measurements, and concepts of noise factor and noise temperature.)

Measurement of Effective Temperature in Microwave Noise Sources, J. S. Wells, W. C. Daywitt, and C. K. S. Miller, IEEE Trans. Instrum. Meas.

IX-13, No. 1, 17-28 (Mar. 1964). (This reference describes the method

of measurement and error analysis.)

Precision Measurement of Antenna System Noise Using Radio Stars, D. F. Wait, IEEE Trans, on I&M, IM-32, No. 1 (Mar. 1983).

Training Programs

Noise measurement seminars are held on an irregular basis on the

basis of perceived need. For example, the most recent seminar held in

Boulder, CO, provided both theoretical and practical instruction on precision noise measurements, including topics such as reference noise

sources; noise measuring systems; characterizing and measuring noise in

passive components, amplifiers, and satellite earth terminals; noise

concepts and measures, such as noise power, noise equivalent flux, and

the ratio of system gain to system noise temperature G/T.

Future Directions

Plans call for the development and provision of noise temperature

measurement services for new frequency ranges to follow the needs of the

communication and other relevant industries, and of defense requirements.

The NBS automated radiometer, a form of total-power radiometer requiring

noise sources at two reference temperatures, will serve as the basis for

a considerable portion of the planned extensions in frequency coverage.

69
Contact Person at NBS

Ramon C. Baird

Electromagnetic Fields Division

303- 497-3301

70
PHASE SHIFT (4.7)

Description of Services

Specific phase shift services listed below are available on a limited basis depending on other demands and staff availability.

Measurements not listed may possibly be provided if sufficient advance

notice is given. Often a measurement technique can be suggested that

will permit the customer to perform calibrations in-house with

appropriate reference to other NBS-supported standards so that

consultation by telephone is recommended as an initial action.

(a) Coaxial Devices

Fixed and variable coaxial two ports are measured on the NBS

modified Automatic Network Analyzer (ANA) over the frequency range 0.1

to 18 GHz. In addition, measurements can be performed with reference to

a precision variable air line at 30 MHz. Items to be calibrated must be

fitted with connectors having a known plane of reference such as the

sexless precision connectors, or Type N connectors meeting Mil C 39012.

The phase angle measured is i)> + 360 n, where n is the integer. The

value of n is not determined.

Limits of uncertainty are

30 MHz 0 - 360° 0.1 - 0.5°

0.1 - 18 GHz 0 - 360° 0.5°

These limits of uncertainty are the sums of systematic and random

errors. The values are dependent upon the particular standard under

calibration. The VSWR of the device and the quality of the connectors

will contribute to the uncertainties of calibration.

(b) Waveguide Devices

In a rectangular waveguide the measurement services are limited to

phase shift difference at frequencies below 18 GHz. Measurements are made on continuously variable waveguide phase shifters with the zero value of the scale as the normal reference position. Since 360

mechanical degrees of rotation represent 720 electrical degrees,

attention should be given to the relationship between dial indication

and actual mechanical position of the rotating vane assembly. The

uncertainty is approximately the same as for coaxial devices.

(c) Baseband Pulse Parameters

NBS offers special test services for several baseband pulse

parameters. These are broken down into four categories: impulse

generator spectrum amplitude, fast repetitive baseband pulse parameters,

network impulse response, and pulse time delay.

The following list indicates the limitations of the service for

measuring the broadband spectrum amplitude output from impulse

generators:

71
Parameter Limits

Frequency range

Frequency spacing

Maximum impulse amplitude

without attenuators

Maximum impulse amplitude

with external attenuators

Spectrum amplitude

Load impedance

Trigger pulse magnitude

Trigger pulse transition time

Trigger to impulse delay

Trigger to impulse jitter

5 MHz to 6 GHz

Af = 5,10,20,50, or 100 MHz

± 400 mV

± 1.2 mV

-15 dBpV/MHz <[S(f)-S ]> + 5 dBpV/MHz 0

50.0

> 200 mV

< 5 ns

75 ns<t

t

<100 ns

< 20 ps

The measurement capabilities for fast repetitive baseband pulses

include pulse amplitude (± 500 mV), pulse rise time and fall time (10 ps

to 1 ps), and pulse duration (10 ps to 1 ps). The customer's device

must generate a repetitive pulse with repetition rate between 100 Hz and

1 GHz.

Network impulse response measurements on coaxial networks, using

pulse techniques, provide data over a 100 kHz to 12.5 GHz frequency

range, and 0 to 40 dB loss or gain range. A wide variety of connectors

can be accommodated. The approximate limits of uncertainty are ± 2% for

all parameters.

NBS offers a special test for pulse time delay from 200 ps 1 ps.

Customer's device must utilize precision coaxial connectors for both

delay ports and, if possible, a driving pulse generator should be

provided.

Documentati on

Evaluation of a Microwave Phase Measurement System, D. A. Ellerbruch, J. Res. Natl. Bur. Stand. (U.S.), 69C (Eng. and Inst.), 1, 55-65

(Jan. -Mar. 1965).

Impulse Generator Spectrum Amplitude Measurement Techniques, J. R. Andrews, IEEE Trans. Instrum. Meas. , 25, No. 4, 280 (Dec. 1976).

Spectrum Amplitude Definition, Generation, and Measurement, J. R. Andrews and M. G. Arthur, Natl. Bur. Stand. (U.S.), Tech. Note 699 (Oct.

1977).

72
Pulse Techniques and Apparatus, Part 1: Pulse Terms and Definitions;

Part 2: Pulse Measurement and Analysis, General Considerations, IEC

Publications 469-1 and 469-2, IEC, Geneva, Switzerland (1974).

IEEE Standard Pulse Terms and Definitions, IEEE Std. 194-1977, and IEEE

Standard on Pulse Measurement and Analysis by Objective Techniques, IEEE

Std. 181-1977, IEEE, New York (July 1977).

Time Domain Automatic Network Analyzer for Measurement of RF and

Microwave Components, W. L. Gans and J. R. Andrews, Natl. Bur. Stand.

(U.S.), Tech. Note 672 (Sept. 1975).

Present Capabilities of the NBS Automatic Pulse Measurement System, W.

L. Gans, IEEE Trans. Instrum. Meas. , IM-25, 384-388 (Dec. 1976).

Pulsed Wavemeter Timing Reference for Sampling Oscilloscope Calibration,

J. R. Andrews and W. L. Gans, IEEE Trans. Instrum. Meas., IM-24, 82

(Mar. 1975).

Modeling of the Feed-Through Wideband (dc to 12.4 GHz) Sampling Head, S. M. Riad and N. S. Nahman, in Dig. 1978 IEEE-MTT-S Int. Microwave Symp.

(Ottawa, Ont. , Canada, June 27-29, 1978).

Deconvolution of Time Domain Waveforms in the Presence of Noise, N. S. Nahman and M. E. Guillaume, Natl. Bur. Stand. (U.S.), Tech. Note 1047

(Oct. 1981).

The Measurement and Deconvolution of Time Jitter in Equivalent-Time

Waveform Samplers, W. L. Gans, IEEE Trans. Inst. Meas., IM-32, No. 1,

126-133, (Mar. 1933).

Training Programs

No formal training activities are scheduled at present. Seminars

such as the Seminar on Waveform Recorder Measurement Needs and

Techniques for Evaluation/Calibration (Boulder, CO 1981) will be held as appropriate.

Future Directions

Plans call for measurement methods to continue to be developed in

response to demonstrated needs of industrial and other clientele.

Potentially relevant technological developments, such as the use of

subpicosecond optical pulses and the electrooptic effect to sample

electrical transients, will be monitored and applied as appropriate to

solve pulse measurement problems.

73
Contact Person at NBS

Cletus Hoer (Coaxial and Waveguide Devices)

Electromagnetic Technology Division

303- 497-3705

or

Ramon C. Baird (Baseband Pulse Parameters)

Electromagnetic Fields Division

303- 497-3301

74
RADIO AND MICROWAVE WAVE POWER MEASUREMENTS (4.8)

Description of Services

Calibrations of coaxial peak pulse power meters from 0.001 to

5000 W at frequencies between 0.95 and 1.25 GHz are made with pulsed rf

waves modulated by a baseband trapezoidal pulse. Limits of other basic

parameters of the pulses are as follows:

Pulse duration range 0.5 to 10 ps

Pulse reptition rate change 100 to 1600 pps

Maximum duty factor 0.0033

Instruments submitted for calibration should have a nominal impedance

of 50 Q , and be fitted with Type N, BNC, HN, or 7- or 14-mm precision

connectors. If other connectors are used, degradation of the uncertainty

limits could result.

Calibration services are also available for thermistor-type bolometer

units having a nominal resistance of either 100 or 200 Q at a bias

current between 3.5 and 15 mA and thermoelectric (TE) power sensor-power

meter units. Calibrations are performed at a nominal power level of 10

mW. Thermistor- type bolometer units have shown adequate stability over

long periods of time (approximately 10 yr. ) and warrant long recalibration

intervals. Two- or three-year recalibration intervals are recommended

once the stability of a bolometer unit has been verified. Thermoelectric

power sensor power meter units must be linear with power level to within

0.02 dB/10 dB on 10 mW range. Only bolometer units designed for low

frequency operation will be calibrated below 100 MHz.

Documentation

A Refined X-Band Microwave Microcalorimeter, G. Engen, J. Res. Natl.

Bur. Stand. (U.S.), 63C, 77-82 (1959).

WR-15 Microwave Calorimeter and Bolometer Unit, M. Harvey, Natl. Bur.

Stand. (U.S.), Tech. Note 618 (May 1972).

WR-10 Millimeter Wave Microcalorimeter, M. Weidman and P. Hudson, Natl.

Bur. Stand. (U.S.), Tech. Note 1044 (June 1981).

A Bolometer Mount Efficiency Measurement Technique, G. Engen, J. Res.

Natl. Bur. Stand. (U.S.), 65C, 113-124 (April-June 1961).

A Transfer Instrument for the Intercomparison of Microwave Power Meters,

G. Engen, IRE Trans. Instrum., 19, 202-208 (Sept. 1960).

A Semi automated Six Port for Measuring Millimeter-Wave Power and Complex

Reflection Coefficient, M. Weidman, IEEE-MTT Trans. MTT-25(12) (Dec.

1977).

Performance Characteristics of an Automated Broad-Band Bolometer Unit

Calibration System, E. Komarek, IEEE-MTT Trans. MTT-25(12) (Dec. 1977).

75
Application of an Arbitrary Six-Port Junction to Power Measurement

Problems, G. Engen and C. Hoer, IEEE Trans. Instrum. Meas. , IM-21,

470-474 (Nov. 1972).

Accurate Microwave High Power Measurements Using a Cascaded Coupler

Method, K. E. Bramall , J. Res. Natl. Bur. Stand. (U.S.), 3 & 4, (Eng.

and Instr.) 181-186 (July-Dee. 1971).

Bolometric Microwave Power Calibration Techniques at the National Bureau

of Standards, R. R. Desch and R. E. Larson, IEEE Trans. Instrum. Meas.,

IM-12(1) (June 1963).

A Method of Determining the Mismatch Correction in Microwave Power

Measurements, G. Engen, IEEE Trans. Instrum. Meas., IM-17(4) (Dec.

1968).

Theory of UHF and Microwave Measurements Using the Power Equation

Concept, G. Engen, Natl. Bur. Stand. (U.S.), Tech. Note 637 (April

1973).

Training Programs

None available.

Future Directions

Service for power levels below 10 mW in coaxial and rectangular

waveguides of frequencies from 10 MHz to 26.5 GHz will be available by

the end of 1985. Extension of dynamic range using 3-port couplers is

being investigated.

Contact Person at NBS

Cletus A. Hoer

Electromagnetic Technology Division

303-497-3705

76
VOLTAGE (4.9)

Description of Services

Calibration services are available for four types of electromagnetic

voltage measuring devices: (1) Thermal Voltage Converters (TVCs), (2)

Peak-to-Peak Detectors, (3) Voltage Comparators, and (4) rf Micropotenti ometers.

o Thermal Voltage Converters

The thermal voltage converter (TVC) category also includes other

devices using thermal detectors such as Rawson RF Voltmeters, Thermal

Transfer Standards, rf Voltage Standards, and AC-DC Transfer Standards.

Most converters have rf-dc differences within ±0.1 percent of zero

at 1 MHz and below. All converters having previous calibration history

that are submitted for recalibration should be evaluated at 1 MHz and

results compared to prior data. If the difference is negligible, no further calibrations are usually necessary below 1 MHz.

Services available for low-frequency

connector are:

rf voltage

TVCs without a built-in "T:

Estimated

Frequency range limits of uncertainty*

(MHz) (V) (±%)

0.03 0.1 to 200 0.05

0.1 0.1 to 200 0.05

0.3 0.1 to 200 0.05

1 0.1 to 200 0.05

3 0.1 to 200 0.1

10 0.1 to 200 0.1

30 0.1 to 200 0.2

100 0.1 to 200 1.0

*No rf-dc differences greater than ± 20 percent will be reported.

This normally limits the calibrations to ;100 MHz and below.

Services available for the high-frequency TVCs with a built-in "T

connector are:

rf voltage Estimated

Frequency range limits of uncertainty

(MHz) (V) (±%)

10, 30, 100 0.1 to 7.5 1

200, 300, 400

500, 600, 700

800, 900, 1000

77
Calibrations having ± 1 percent uncertainty are performed only on the new high frequency thermal voltage converters with a "T" connector

incorporated in the converter housing. The measurement reference plane

is at the Type "N" male output connector.

o Peak-to-Peak Detectors

Measurements on peak-to-peak detectors are performed from 100 kHz

to 500 MHz and are referenced to the center of a GR 874 "T" connector.

A 50 kHz ac signal is applied instead of dc. The services available

are:

Frequency

(MHz)

Applied rf voltage

for "0" detector output

Estimated limits

of uncertainty

(%)

0.1, 0.3, 1.0 1.2 V p-p 0.15

3, 10 0.20

30 0.30

50 0.60

100, 200, 300, 400, 500 1.10

o Rf Voltage Comparators

Special tests are performed on rf voltage comparators using TVCs

and micropotentiometers from 100 kHz to 1 GHz at voltages ranging from

10 mV to 20 V. Several calibration options are available to the customer.

Therefore, consultations by telephone or written correspondence is

suggested before the comparator is submitted for calibration.

o Rf Micropotentiometers

Rf micropotentiometers are usually calibrated at their nominal

rated output voltages. Frequencies suggested for a normal calibration

are 5, 100, 300, 400, 500, 700, and 900. As a special service, rf

micropotentiometers with output voltages greater than 200 pV can be

calibrated from 0.05 to 1000 MHz, with reduced limits of uncertainty

varying from ±0.2 percent to ± 2 percent. This uncertainty is dependent

on frequency, output level and the rf-dc difference vs. frequency

response.

Rf micropotentiometers having resistive elements greater than 10

mfi, in combination with thermoelement housings between 5 and 100 mA,

usually have rf-dc differences within ± 1 percent of zero at 5 MHz.

Since the rf-dc difference approaches zero below 5 MHz, calibrations at

50 kHz and 5 MHz would suffice to determine interpolated points of

interest between 50 kHz and 5 MHz, with no appreciable loss of accuracy.

Documentation

NBS rf Voltage Comparator, L. D. Driver, F. X. Ries, G. Rebuldela, Natl.

Bur. Stand. (U.S.), NBSIR 78-871, 12 pages (Dec. 1978).

78
Thermal Voltage Converters for Accurate Voltage Measurements to 30

Megacycles Per Second, F. L. Hermach and E. S. Williams, Reprint from

Communication and Electronics, 6 pages (July 1960).

Thermal Converters as AC-DC Transfer Standards for Current and Voltage

Measurements at Audio Frequencies, F. L. Hermach, J. Res. Natl. Bur.

Stand. (U.S.), 48, 121-138 (1952).

Accurate Radio Frequency Microvoltages, M. C. Selby, Communication and

Electronics, 158-164 (May 1953).

High Frequency Microvolt Measurements, F. X. Ries and G. Rebuldela, ISA

Preprint 37.2.63, 5 pages (Sept. 1963).

Training Programs

None.

Future Directions

The feasibility of using six-ports in performing TVCs and rf

micropotentiometer calibrations will be investigated.

Contact Person at NBS

Cletus Hoer

Electromagnetic Technology Division

303-497-3705

79

TIME AND FREQUENCY (5.1 - 5.2)

Description of Services

NBS offers several around-the-clock time and frequency dissemination services to the general public. This is accomplished primarily via

the radio broadcasts of stations WWV, WWVH, and WWVB and a time code

disseminated from the GOES satellite system. WWV's signal is also

offered by a telephone service, not toll-free, by dialing (303) 499-

7111. A similar service from WWVH is available by dialing (808) 335-

4363 in Hawaii.

Broadcasts from WWV and WWVH can be received on conventional shortwave receivers nearly anywhere in the world. Broadcast frequencies

include 2.5, 5, 10, and 15 megahertz for both stations and 20 megahertz

from WWV only. Accuracies within one millisecond can be obtained from

these broadcasts if one corrects for the station's distance from the

receiver. These services also provide standard frequencies, a BCD time

code, astronomical time corrections, and certain public service announcements for other government agencies. The telephone service offers to

individuals without receivers, the capability of obtaining NBS time and

audio frequency signals. The caller can receive a time signal accurate

to 30 milliseconds or better, about the maximum delay in cross-country

telephone lines. WWVB offers a direct path signal of greater accuracy

than WWV or WWVH, but a special 60- kilohertz low frequency receiver is

required. WWVB's signal is a binary coded system, needing special

decoding equipment. These broadcast services are coordinated with

similar operations in other countries through active participation in

the international CCIR organization.

NBS time and frequency signals covering about 40 percent of the

earth have been relayed via geostationary satellite since 1975 in an experimental service. More than 8 years of experience has shown that

such a system can offer continuous time and frequency reception that is

much more dependable than ground-based AM and FM radio stations, is free

from propagation anomalies, and has a better-than-100-microsecond

accuracy.

An enhanced level of calibration activity has been encouraged since

1982. Those calibrations which require the special facilities of the

National Bureau of Standards and those which require traceability to the

national standards are actively welcomed.

Two new time and frequency measurement assurance services were started in 1983. They permit the user to obtain time and frequency

traceable to the NBS with greater precision and less work than previously

possible. The new services are suitable for users who require time

transfer accuracies in the 3 nanosecond to 1 microsecond range or frequency calibration capability in the 1 part in 10 11 to 1 part in 10 11 range. However, even applications which do not require this level of

precision may take advantage of these services because of their high

degree of automation, simplicity of use, and a degree of support from

NBS.

81
Time requirements at the 1 microsecond level and frequency calibration requirements at the part in 10 11 to part in 10 12 level can be

satisfied using low frequency radio signals from broadcast stations such

as WWVB or Loran-C. The NBS service consists of assisting the user to

set up a low frequency receiver and data logger system which is the most

appropriate for his needs and his location. A typical system would

contain a receiver, microcomputer, disc units and printer-plotter. The

user's responsibility is to provide dedicated phone line and modem so that his data can be compared with data recorded at NBS, thus providing

assurance that the measurements are valid. The user will also receive a bulletin, either by telephone or by mail, which reports the performance

of many of the accurate signal sources. To assist the user in getting

the most out of this system NBS will provide specific training on the

actual equipment involved in its Seminar on Frequency Measurements and

Calibrations. This will assist the user in resolving system failures.

The second service, based upon the NBS designed GPS receiver,

provides much higher precision time and frequency data and a greater

degree of automation. The receiver which is located at the users facility communicates its data automatically to an NBS computer which

stores the raw data, determines which data elements are suitable for

time transfer calculations and provides an optimally filtered value for

the time and frequency of the user's clock with respect to the NBS

Atomic Time Scales. The user is given an account on one of the NBS

computers through which he may access both the raw data and the results

of the NBS analysis. Tests between receivers in California, Colorado,

Wyoming, France, Germany, and Spain, have demonstrated an ability to

perform time comparisons with a precision of 3 nanoseconds, and

frequency comparisons with a precision of 1 part in 10 14

.

In conjunction with its new time scale algorithms NBS has developed

a time and frequency measurement system which is unsurpassed in many of

its capabilities. This new system has vastly improved capability of

calibrating any clock that might be sent to NBS. The full accuracy of

the NBS time scale and primary frequency standard is readily available

and measurements are made automatically every two hours on a clock being

calibrated. These data are logged in the NBS time scale computer and

the standards' characteristics and performance are readily documentable.

Similarly, the person for whom the clock is being calibrated can be

given an account in one of the NBS computers through which he may access

the data in real time. This has proven to be very useful.

Precision oscillator frequency calibrations are available at

nominal frequencies of 5.0, 10, 10.23 MHz with reference standard

accuracy of the order of 1 x 10 -13

. Precision oscillators may be

characterized in two ways:

(a) TIME DOMAIN measurements of the stability, a (t) for signals

of the above nominal frequency. When comparing the unknown precision

oscillator with the NBS standard the measurement limit is a (t)<2 x 10 12

x ^ where x is the sample time of the comparison in seconds. The

long-term (1 day and longer) stability of the NBS frequency reference is

nominally 1 x 10 -14 .

82
(b) FREQUENCY DOMAIN measurements of phase noise, S (f) for signals

of the above nominal frequency. Hz measurements of the order of -150 db are possible for f = 1 Hz and -175 db for f = 1 kHz.

Documentati on

Time and Frequency User's Manual, G. Kamas and S. L. Howe, editors,

Natl. Bur. Stand. (U.S.), Spec. Publ. 559 (1979).

A New Frequency Measurement Service Offered by the National Bureau of

Standards, G. Kamas and J. L. Jespersen, 37th Annual Frequency Control

Symposium, in press.

Training Programs

Two separate frequency measurement seminars are available.

Seminar on Frequency Measurements and Calibrations

This is a new seminar that incorporates new material into the Time

and Frequency User's Seminar given in previous years. It is intended

for engineers and standards lab technicians involved in making frequency

calibrations. The course will be taught at a practical level to satisfy

those new in the field as well as more experienced users. Methods

taught will use commercially-available equipment.

Topics covered:

o Crystal oscillator calibration

o Applications of frequency counters

o How to choose a frequency calibration source

o Care and use of frequency sources

o Using LORAN-C and WWVB for frequency calibrations

o Time and frequency measurement assurance services at NBS

o Organization of time and frequency in the U.S.

o NBS, USNO, and other publications

Although all of the above subjects will be covered, emphasis will be on making practical frequency calibrations and measurements.

Seminar on Frequency Standards and Clocks

This seminar is intended for program managers, planners, and systems

engineers.

Topics covered:

o A history of time scales (background)

o National and international structure of time and frequency

(background)

o Concepts, definitions, and measures of short-term frequency

stability (theoretical)

o Techniques for measuring short-term frequency stability and noise

in oscillators

83
o Review of performance of commercial frequency standards (what's

available, specifications)

o Limitations of present-day atomic frequency standards

o The process of timekeeping (clock modeling)

o Time coordination: methods for comparison of time scales

o Propagation effects on radio transmissions

o Optical techniques and propagation effects

Future Directions

Research activities in the NBS Time and Frequency Division will

lead to improved calibration services in the future. For example,

through the basic research program on laser cooled mercury ions, NBS

scientists hope to develop more stable clocks with a 100-fold improvement in accuracy anticipated.

Based on the experiences gained with the present offerings and from

close contact with the NCSL and others, NBS expects to expand its

calibration services being offered to the public.

Other publications forthcoming will include articles for the

popular electronic trade press describing the new calibration services

to both the electronics industry and the communications/TV engineering

community.

Contact Person at NBS

Roger Beehler

Time and Frequency Division

303- 497-3335

84
LABORATORY THERMOMETERS (7.1)

Description of Services

This service provides for the calibration of a variety of thermometers

covering the range from -196 to +538 °C. The majority of the thermometers

calibrated are 1 i quid- in-glass , but other thermometers (thermistors,

industrial platinum resistance thermometers, thermocouples) are calibrated

as well. A limited number of special tests falling outside the formal

structure of all the other temperature calibrations are performed at the

request of the customer. The thermometers to be calibrated are placed

in a constant temperature bath along with the NBS primary standard - a calibrated platinum resistance thermometer. The primary standard

maintains calibrations traceable to the International Practical Temperature

Scale (1968) with an accuracy of 5 mK at the lower range and ~2 mK at

the higher range. The thermometers are provided with a Report of

Calibration or Report of Test which gives the calibration of the customer

thermometer with comparable accuracy.

TYPE OF THERMOMETER

(Total Immersion)

Mercury liquid- in-glass

(graduations: 1-2 °C)

Mercury 1 i quid- in-glass

(graduations: 0.1 - 0.2

Organic 1 i quid- in-glass

(graduations: 1 °C)

Thermistor

Documentation

RANGE UNCERTAINTY

0 to 300 °C ±0.2 to ±0.3 °C

300 to 500 °C ±0.5 to ±1.0 °C

0 to 100 °C ±0.03 to ±0.05 °C

-200 to 0 °C ±0.2 to ±0.5 °C

According to customer request

Li quid- in-Glass Thermometry, Jacquelyn A. Wise, Natl. Bur. Stand.

(U.S.), Monogr. 150, 30 pages (Jan. 1976).

Training Programs

Twice a year NBS offers a 5-day Precision Thermometry Seminar in

which one day is devoted to 1 i quid- in-glass thermometry. That day

includes both lectures and "hands on" laboratory experience.

Future Directions

The demand for liquid-in-glass thermometer calibrations has been

holding steady at about 800 calibrations per year. We do not anticipate

a significant change in demand here, but we suspect that the demand for

other laboratory thermometers (industrial resistance thermometers and

thermistors) may increase. Calibration services at present staffing

levels can meet these new demands if they amount to less than 50/year.

If the demand increases beyond that point NBS may have to consider

85
additional staff or a MAP program. No automation of L-I-G thermometers

is contemplated, although automation of the Calibration Report is

underway. New documentation is planned that will guide State calibration

laboratories in establishing iji situ temperature calibration facilities.

Contact Person at NBS

Robert Soulen

Temperature and Pressure Division

301- 921-3315

86
THERMOCOUPLES AND THERMOCOUPLE MATERIALS (7.2)

Description of Services

Calibration services for all commonly used types of thermocouples

are provided by NBS from -196 to +2100 °C depending upon the wire or thermocouple type. The thermocouples are calibrated by one or a combination of three general methods, depending on the thermocouple type, the

temperature range, and the accuracy required. All three methods provide

traceability to the IPTS-68. In the first method, thermocouples are calibrated by comparison with a standard thermocouple maintained at NBS.

In the second method, thermocouples are calibrated by comparison with a standard platinum resistance thermometer. In the third method, thermocouples are calibrated at three defining temperatures on the IPTS - the

freezing points of Zn, Ag, and Au, as well as at 630.74 °C. Below 0 °C

the thermocouple calibration is carried out in a cryostat, while above

0 °C stirred liquid baths, metal freezing-point cells, and electric

tube- type furnaces are employed for the calibrations. Vacuum or inert

gas furnaces are also available for testing thermocouples. An automatic

data acquisition system has been developed to record the test data

during calibrations performed by the comparison method (the first method

described above). The calibration data are processed on a laboratory

computer, and calibration tables giving values of the thermocouple emf

at one degree intervals are provided for Types B, S, R, and T thermocouples.

THERMOCOUPLE TYPE RANGE

(°C)

UNCERTAINTY

S 0 to 1450 °C ±0.2 °C at freezing points

±0.3 °C (0 to 1100 °C)

±2 °C at 1450 °C

S & R 0 to 1450 °C ±0.5 °C (0 to 1100 °C)

±2 °C at 1450 °C

B 0 to 1750 °C ±0.5 °C (600 to 1100 °C)

±2 °C at 1450 °C

±3 °C at 1750 °C

E -196 to 538 °C

0 to 1000 °C

±0.1 to ±0.2 °C

±1 °C

J -196 to 538 °C

0 to 760 °C

±0.1 to ±0.2 °C

±1 °C

K -196 to 538 °C

0 to 1100 °C

±0.1 to ±0.2 °C

±1 °C

T

-169 to 300 °C

0 to 400 °C

±0.1 to ±0.2 °C

±1 °C

87
Documentation

Thermocouple Reference Tables Based on the IPTS-68, R. L. Powell, W. J. Hall, C. H. Hyink, Jr., L. L. Sparks, G. W. Burns, M. G. Scroger, and

H. H. Plumb, Natl. Bur. Stand. (U.S.), Monogr. 125, 410 pages (1974).

American National Standard, Temperature Measurement Thermocouples,

ANSI-MC96. 1-1982 (Instrument Society of America, Research Triangle Park,

1982).

ASTM Standard E230-77, Temperature-Electromotive Force (EMF) Tables for

Thermocouples, 1983 Annual Book of ASTM Standards, 14.01, 271 (American

Society for Testing and Materials, Philadelphia, 1983).

Accurate Thermocouple Thermometry, L. A. Guildner and G. W. Burns,

High Temperatures - High Pressures, 11, 173 (1979).

Methods of Testing Thermocouples and Thermocouple Materials, W. F. Roeser and S. T. Lonbarger, Natl. Bur. Stand (U.S.), Circular 590, 13

pages (1958).

ASTM Standard E220-80, Standard Method for Calibration of Thermocouples

by Comparison Techniques, 1983 Annual Book of ASTM Standards 14.01, 255

(American Society for Testing and Materials, Philadelphia, 1983).

International Electrotechnical Commission Standard, Thermocouples, Part

1: Reference Tables, IEC Publication 584-1 (Bureau Central de la

Commission Electrotechnique Internationale, Geneva, 1977).

Manual on the Use of Thermocouples in Temperature Measurement, ASTM STP

470B, (American Society for Testing and Materials, Philadelphia, 1981).

Training Programs

Twice a year a 5-day Precision Thermometry Seminar is offered in

which one day is devoted to thermocouples. Lectures and "hands on"

laboratory simulations of calibration are included.

Future Directions

NBS will continue to provide routine calibration services for

various types of thermocouples. We will continue to update and expand

the present calibration services to meet the needs of our customers. We

note that special, non-routine requests for special thermocouple tests,

such as emf stability testing of thermocouples and thermocouple devices,

have grown during the past two years. We intend to modify existing

equipment when practical and develop new techniques as needed in order

to satisfy as many future requests of this nature as possible. New

documentation is planned which will provide temperature-emf reference

tables for Ni-18% Mo/Ni-0.8% Co thermocouples and a description of a calibration method for expendable, immersion thermocouple devices.

88
Contact Person at NBS

Robert Soulen

Temperature and Pressure Division

301- 921-3315

89
STANDARD PLATINUM RESISTANCE THERMOMETERS (7.3)

Description of Services

NBS provides calibration services for standard platinum resistance

thermometers (SPRTs) from 13.81 to 903 K. Both long-stem and capsuletype SPRTs are calibrated providing direct access to the IPTS-68.

Measurement Assurance Programs are provided at two different levels. At

the highest level of accuracy, the MAP consists of sending three

calibrated SPRTs to the participant's laboratory where they are measured

and then returned to the NBS for recalibration. The results are compared and a report to the participant is issued. Where necessary,

suggestions for improvements in measurement or documentation are made.

The measurements at most of the laboratories agree with NBS to within ±5

mK. In the lower level of accuracy MAP, NBS is conducting an assessment

of industrial laboratories at the 0.1 to 0.01 K level through the

exchange of SPRTs.

The reproducibility of the calibration measurements of SPRTs is

better than ±0.1 mK and the accuracy of overall calibration is ±1 mK.

The triple point of water cells used for calibration of SPRTs are reproducible to 50 pK or better while the zinc and tin freezing point

cells agree to within ±0.1 mK. The precision of comparison calibration

of long-stem type SPRT in terms of the reference standard SPRTs at the

oxygen boiling point (-183 °C) is better than ±0.1 mK. The stability of

the reference SPRTs in this temperature range is also about ±0.1 mK.

The NBS temperature scale in the range 13 to 90 K is based on stable

reference standards SPRTs of the capsule type and has a precision of

about ±0.1 mK down to about 20 K. Below 20 K, the precision degrades to

about ±0.3 K as the SPRTs become less sensitive.

Documentation

Platinum Resistance Thermometry, J. L. Riddle, G. T. Furukawa, and

H. H. Plumb, Natl. Bur. Stand. (U.S.), Monogr. 126, (Apr. 1973).

Reproducibility of Some Triple Point of Water Cells, G. T. Furukawa and

W. R. Bigge, Temperature, Its Measurement and Control in Science

and Industry, Vol. 5 (American Institute of Physics, New York, NY,

1982), 291-297.

Investigation of Freezing Temperatures of National Bureau of Standards

Tin Standards, G. T. Furukawa, J. L. Riddle and W. R. Bigge, Vol. 4 of

Temperature (Instrument Society of America, Pittsburgh, PA,

1972), Part 1, 247-263.

Comparison of Freezing Temperature of National Bureau of Standards

SRM-740 Zinc Standards, G. T. Furukawa and J. L. Riddle, Comite

Consul tatif de Thermometrie, May 9-11, 1978, Sfevres, France.

The International Practical Temperature Scale of 1968 in the Region

13.81 K to 90.188 K as Maintained at the National Bureau of Standards,

G. T. Furukawa, J. R. Riddle, and W. R. Bigge, J. Res. Natl. Bur. Stand.

(U.S.), 77A , 309-332 (May-June 1973).

90
The International Practical Temperature Scale of 1968 in the Region

90.188 K to 903.89 K as Maintained at the National Bureau of Standards,

G. T. Furukawa, J. L. Riddle, and W. R. Bigge, J. Res. Natl. Bur. Stand.

(U.S.), 80A, 477-504 (May- June 1976).

Standard Reference Materials: Application of Some Metal SRM's as Thermometric Fixed Points, G. T. Furukawa, J. L. Riddle, W. R. Bigge and

E. R. Pfeiffer, Natl. Bur. Stand. (U.S.), Spec. Publ. 260-77 (Aug.

1982).

A Measurement Assurance Program - Thermometer Calibration, G. T. Furukawa and W. R. Bigge, in Testing Laboratory Performance, Evaluation

and Accreditation, Natl. Bur. Stand. (U.S.), Spec. Publ. 591, 137-145

(Aug. 1980).

Training Programs

Two days of the twice-annual Precision Thermometry Seminar are given to platinum resistance calibration. Instruction is provided on

all aspects of this form of thermometry. Laboratory simulation of

calibrations is also given.

Future Directions

Plans include the automation of the calibration service and

inclusion of some check standards (additional fixed points) in the

calibration procedure. Fixed points under examination include Krypton

triple point (116 K), Xenon triple point (161 K) , Mercury triple point

(234 K), Indium freezing point (430 K) , and Cadmium freezing point

(594 K).

Access to a second temperature scale, the EPT - 76 is now provided

by calibration of resistance thermometers from 0.5 to 30 K. The

traceability to the scale is ~ 1 mK over this range. The calibration

service is fully automated and serves as a model for future automation

of the IPTS-68 calibration. An NBS Special Publication describing the

NBS EPT-76 and calibration procedure is expected in FY84.

Contact Person at NBS

Robert Soulen

Temperature and Pressure Division

301-921-3315

91
RADIATION THERMOMETRY (7.4)

Description of Services

These calibration services provide access to the International

Practical Temperature Scale of 1968 (IPTS-68) as realized by NBS for the

temperature range 800 °C to 4200 °C. High precision monochrometric

visual and automatic optical pyrometers are calibrated in the

temperature range of 800 °C to 4200 °C. Uncertainties in routine

testing vary from ±3° at 1064 °C, to ±8° at 2800 °C, to ±30° at 4200 °C.

Ribbon filament lamps are calibrated using the NBS photoelectric

pyrometer, and reports of brightness temperature at 655 nm versus direct

current are issued. Uncertainties in routine testing vary from ±1.5° at

1064 °C to ±3° at 2300 °C. In FY-83, 15 tests ($20K) were performed.

* The radiation thermometry portion of IPTS-68 is defined in terms of

a fixed temperature for the freezing point of gold (1064.43 °C) and the

Planck equation for the radiation of a blackbody source. In practice,

temperature scales are realized by constructing 1) a gold point blackbody

and 2) a variable temperature blackbody and then measuring spectral

radiance ratio at a red wavelength (approximately 650 nm) in terms of

the Planck equation. Gold point blackbodies are reproducible at ±0.02°,

but the temperature assignment of the freezing point of gold is un- certain by about ±0.5°. The spectral radiance ratio measurements can be

performed with an uncertainty of 0.2-.3%. Higher accuracies than

available in the routine tests described above can be provided as spectral tests subject to the IPTS uncertainties noted. Calibrations at

wavelengths other than 650 nm can be provided in the wavelength range

250 nm to 2500 nm subject to an additional uncertainty due to the

quality of the variable temperature blackbody. Absorbing glass filters

used for range changing in optical pyrometers can also be calibrated as special tests.

Documentati on

The publications listed below describe the theory and methods of

optical pyrometry as well as the instrumentation and procedures NBS uses

to provide routine calibrations.

The International Practical Temperature Scale of 1968, Amended Edition

of 1975, Metrol ogia, 12, 7-17 (1976).

High-Accuracy Spectral Radiance Calibration of Tungsten-Strip Lamps, H. J. Kostkowski, D. E. Erminy, and A. T. Hattenburg, Advances in

Geophysics, 14, 111-127 (1970).

Theory and Methods of Optical Pyrometry, H. J. Kostkowski and R. D. Lee,

Natl. Bur. Stand. (U.S.), Monogr. 41 (Mar. 1962).

The NBS Photoelectric Pyrometer and Its Use in Realizing the International Practical Temperature Scale above 1063 °C, R. D. Lee,

Metrol ogia, 2, No. 4, 150-162 (Oct. 1966).

92
Vacuum Tungsten Strip Lamps with Improved Stability as Radiance Temperature, T. J. Quinn and R. D. Lee, 5th Symposium on Temperature, 1971,

Instrument Soc. Am. 395-411.

Training Programs

At the present time, no training programs are offered by NBS.

Future Directions

Two research projects are currently being pursued in pyrometry. A

new, state-of-the-art, photoelectric pyrometer is being constructed. It

will incorporate a multi -wavelength capability, redundant components

(filters and lamps) for statistical control, on-line computer control

and data reduction, built-in linearity checks for IPTS realizations and

as a goal, will reduce uncertainties by about a factor of 10. The

second project involves the recently invented optical fiber thermometer.

This device bridges the ranges covered by contact thermometers (thermocouples and platinum resistance thermometers) and optical pyrometers.

Preliminary experiments indicate that the optical fiber thermometer

offers precisions of a few hundredths of a degree and thus it holds out

the promise of substantially improved temperature measurements in the

range 500 °C to 2000 °C. As the results of the pyrometry research

program are incorporated in the routine calibration services,

appropriate documentation will be prepared.

Contact Person at NBS

Donald McSparron

Radiometric Physics Division

301-921-3613

93
RADIOMETRIC STANDARDS (7.5)

Description of Services

These calibration services, provide basic radiometric and

spectroradiometric standards for the national measurement system.

Tungsten, ribbon filament lamps (30A/T24/13) are provided as lamp

standards of spectral radiance. The lamps are calibrated at 33 wave- lengths from 225 to 2400 nm, with a target area 0.6 mm wide by 0.8 mm

high. Radiance temperature range from 2675 K at 225 nm to 2495 K at 650

nm to 1650 K at 2400 nm, with corresponding uncertainties ranging from

3% to 1% to .5%. Lamp standards of spectral irradiance are provided in

two forms. Tungsten filament, 1000-watt quartz halogen type FEL lamps are calibrated at 26 wavelengths in the range 250 to 1600 nm. At the

working distance of 50 cm, the lamps produce 0.2 W/cm3 at 250 nm, 220

W/cm3 at 900 nm and 115 W/cm3 at 1600 nm, corresponding uncertainties

range from 2.5% to 1%. Deuterium lamp standards of spectral irradiance

are also provided calibrated at 16 wavelengths from 200 to 350 nm. At

the working distance of 50 cm, the spectral irradiance produced by the

lamp ranges from about 0.5/cm3 at 200 nm to 0.2 W/cm3 at 250 to 0.06

W/cm3 at 350 nm. The deuterium lamps are intended primarily for the

spectral region 200 to 250 nm. The approximate uncertainty relative to

SI units is 6% at 200 nm and 3% at 250 nm. The approximate uncertainty

in relative spectral distribution is 3%. It is strongly recommended

that the deuterium standards be compared to an FEL tungsten standard over the range 250 to 300 nm each time the deuterium lamp is lighted to

take advantage of the accuracy of the relative spectral distribution.

Absolute spectral responsivity calibrations can be obtained by

leasing one of the NBS Detector Response Transfer and Intercomparison

Packages (DRTIPs). This is a wel 1 -characterized radiometer that

utilizes a silicon photodiode as the detector element. Its calibration

is reported in units of A/W at a number of wavelengths in the 250-1064

nm range. A precision aperture is provided for calibrations in units of

A cm2 /W. The duration of the lease is enough to allow for the transfer

of the calibration to a laboratory's own in-house standards, and for the

performance of specific diagnostic tests to check their capability in

spectral response transfer measurements.

Spectroradiometric source calibrations are performed on the

Facility for Automatic Spectral Calibrations (FASCAL). This fully

automated instrument has the capability of performing spectral radiance

measurements from 200 to 2500 nm, radiance temperature from 1050 K to

2800 K, and adjustable spectral bandpass down to 0.1 nm. Spectral

irradiance measurement capability from 200 to 1600 nm at flux levels

down to 0.1 W/cm3 is also available in this instrument. For both

spectral radiance and spectral irradiance measurements a wide variety of sources and measurement geometries are possible. Special tests

utilizing the capabilities of FASCAL are occasionally performed

depending on the availability of the equipment and associated personnel.

At present the DRTIP calibration is based on electrical substitution radiometry using cw laser lines and several atomic emission lines

94
as the monochromatic radiation sources for the characterization measurements. The absolute spectral response is reported at the 10 nm intervals from 250 to 960 nm, and at two discrete wavelengths outside

this range (1014 and 1064 nm). At present the estimated uncertainty

ranges from 1 to 6%, depending on the wavelength and the particular

radiometers. The radiometers cover a range of detector current from 103

to 10 6 A (full scale). This corresponds to a radiant power range of

about 10 2 to 10 s W. The lowest resolvable power depends on the resolution of the voltmeter used to read the radiometers output (10 = full

scale).

Due to the recent development of a simple and accurate technique

(the silicon photodiode self-calibration procedure) one can measure

directly the photon to electron conversion efficiency of a silicon

photodiode. Greater accuracy is possible, but not offered as a routine

service. This is because the user can easily repeat the selfcalibration procedure in their own laboratory within an uncertainty of

±0.2% (400 to 700 pm) without the necessity of an NBS standard.

Facilities to perform radiometric calibrations in the infrared, 1

to 15 micrometers, are also available. Three facilities are available

and their capabilities are summarized below. Infrared radiometry is

very demanding and usually involves a substantial R&D component. Therefore such work is performed as special tests and is often very expensive

($10K to $20K)

Faci 1 ity 1 2 3

Source Ambient

to 77 K, 10-4

torr

20 K, lO"8 torr Ambient (dry

chamber) to

77 K, 10-4 torr

Radi ometer

envi ronment

Ambient 20 K, 10-8 torr Ambient (dry

chamber)

Detector Thermopile or

PbS (77 K)

Absolute Commerci al

I.R. radiometer

Spectral

range

1 to 15

mi crometers

Total 3 to 10

mi crometers

Spectral

detai

Conti nuous

(0.1 to 1 micrometer resolution)

None

(total flux)

Di screte

(narrow band

f i 1 ters)

Max. physical

size of source lxlxl m 10x10x10 cm 20x20x20 cm

Sensitivity 0. 01 degrees

at 600 K

10~9 watts 0.02 degrees

at 300 K

Source

temperature

350 to 1300 K 150 to 600 K 225 to 450 K

95
Max. source aperture

About 25 mm 1 mm about 25 mm

Measurement

technique

Comparison to

reference

blackbodies

Absolute radiant

power measurement

Comparison to

reference

Goniometry Yes No Yes

Approximate

radiometric

quantity

Spectral radiance

(W m

-2 sr_1 nm**2

) (W sr-1 ) measured

Axial radiant

intensity

Spectral radiance

(W nr*1 sr

-1 nm-1 )

Documentation

In addition to the documentation listed below, ad hoc write-ups are available from the Radiometric Physics Division of NBS describing the

calibration procedure and uncertainty from 1) lamp standards of spectral

radiance, 2) type FEL lamp standards of spectral irradiance, and 3)

deuterium lamp standards of spectral irradiance.

High-Accuracy Spectral Radiance Calibration of Tungsten-Strip Lamps, H. J. Kostkowski, D. E. Erminy, and A. T. Hattenburg, Advances in

Geophysics, 14, 111-127 (1970).

The International Practical Temperature Scale of 1968, Metrologia, 5,

35-44 (1969).

Corrections in Optical Pyrometry and Photometry for the Refractive Index

of Air, W. R. Blevin, Metrologia, 8, 146-147 (1972).

The 1973 NBS Scale of Spectral Irradiance, R. D. Saunders and J. B. Shumaker, Natl. Bur. Stand. (U.S.), Tech. Note 594-13 (U.S. Government

Printing Office, Washington, DC, 1977).

Spectral Irradiance Standard for the Ultraviolet: The Deuterium Lamp,

R. D. Saunders, W. R. Ott , and J. M. Bridges, Appl . Opt., 17, 593-600

(1978).

The NBS Detector Response Transfer and Intercomparison Package: The

Instrumentation, M. A. Lind, E. F. Zalewski, and J. B. Fowler, Natl.

Bur. Stand. (U.S.), Tech. Note 950 (U.S. Government Printing Office,

Washington, DC, 1977).

Proc. of the Electro-Opt. and Laser Conf. , M. A. Lind, (Industrial and

Scientific Conference Management, Chicago, IL, 1976), p. 55.

Fundamental Principles of Absolute Radiometry and the Philosophy of this

NBS Program (1968 to 1971), J. Geist, Natl. Bur. Stand. (U.S.), Tech.

Note 594-1 (U.S. Government Printing Office, Washington, DC, 1972).

96
Spectral Radiometry: A New Approach Based on Electro-Optics, J. Geist,

M. A. Lind, A. R. Schaefer, and E. F. Zalewski, Natl. Bur. Stand.

(U.S.), Tech. Note 954 (U. S. Government Printing Office, Washington,

DC, 1977).

Silicon Photodiode Absolute Spectral Response Self-Calibration, E. F. Zalewski and J. Geist, Appl. Opt., 19, 1214 (1980).

Spectral Response Self-Calibration and Interpolation of Silicon

Photodiodes, J. Geist, E. F. Zalewski, and A. R. Schaefer, Appl. Opt.

20, 3795 (1980).

Silicon Photodiode Absolute Spectral Response - Self-Calibration Using a Filtered Tungsten Source, C. G. Hughes, III, Appl. Opt., 21, 2129

(1982).

Silicon Photodiode Device with 100% External Quantum Efficiency, E. F. Zalewski and C. R. Duda, Appl. Opt., 22, 2867 (1983).

Training Program

At the present time, no training programs are offered by NBS.

Future Directions

A program is now well underway to increase the efficiency of

realization of the NBS scales of spectral radiance and spectral irradiance.

It is envisioned that the techniques used to increase the efficiency of

scale realizations will also allow extension of the spectral irradiance

scale to 2500 nm.

In the area of detector spectral response, research on the physics

of junction photodiodes is directed at extending the present selfcalibration procedure into the UV and IR spectral regions. Collaborative

efforts with scientists in Australia and at the University of Maryland

have led to improved measurements of the quantum yield of silicon in the

UV and a better understanding of the physics in this region. In the IR, a collaborative effort with the Purdue University Department of

Electrical Engineering holds promise of producing, in the very near

future, high quality germanium photodiodes capable of being

self-calibrated out to about 1.4 pm.

In the longer wave infrared, a number of research proposals have

been prepared to extend the wavelength range, increase the sensitivity

of the NBS apparatus, and investigate the sources of systematic error. These proposals have been submitted to other government agencies.

Progress is dependent on obtaining such outside support.

Two additional documents are in preparation, one will describe the

realization of the NBS scale of spectral radiance and the other will

describe the equipment and capabilities of FASCAL.

97
Contact Person at NBS

Donald McSparron

Radiometric Physics Division

301- 921-3613

98
NEAR AND VACUUM ULTRAVIOLET RADIOMETRIC STANDARDS (7.6)

Description of Services

NBS maintains a collection of secondary standard sources such as argon maxi-arcs, argon mini-arcs, and deuterium arc lamps in the near

and vacuum ultraviolet radiometric standards program to provide calibrations for user supplied services. The calibrations of these sources are traceable to a hydrogen arc whose radiance is calculable and which NBS

maintains as a primary standard. The collection also includes tungsten

strip lamps and tungsten halogen lamps whose calibrations are done by

another group at NBS and are based on a blackbody rather than our hydrogen arc. Customer supplied sources are calibrated in both radiance

and irradiance by comparing them with our secondary standards.

Argon arcs are used to calibrate other sources in the wavelength

range 115 nm to 330 nm for radiance and 140 nm to 330 nm for irradiance.

The lower wavelength limit is determined in radiance by the cutoff of

the magnesium fluoride windows used in the arcs and in irradiance by the

decrease in signal produced by the addition of a diffuser. Deuterium

arc lamps are used in the range 165 nm to 200 nm, with the low wavelength

cutoff due to the onset of blended molecular lines and the high wavelength

limit the starting point of the range of another calibration group at

NBS. The tungsten lamps are used at 250 nm and above, since their

signals are too weak at shorter wavelengths. It should be noted that

the wavelength range of the NBS arcs partially overlap the range of

tungsten lamps, thus providing an independent check on calibrations.

Documentati on

VUV Spectral Irradiance Calibrations: Method and Applications, Optics

Letters, 5, 225 (1980).

Spectral Irradiance Standard for the Ultraviolet: The Deuterium Lamp,

Appl . Opt., 17, 593 (1978).

Spectral Radiance Calibrations Between 165-300 nm: An Interlaboratory

Comparison, Appl. Opt., 16, 1788 (1977).

VUV Radiometry. 3: The Argon Mini-Arc as a New Secondary Standard of

Spectral Radiance, Appl. Opt., 16, 367 (1977).

NBS UV Radiometric Standards, Natl. Bur. Stand. (U.S.), Spec. Publ. 456,

107 (1976).

Training Programs

No formal training programs are available. However, occasiona'ly

users come to NBS with sources for calibration, but are unfamiliar with

their sources. NBS has arranged for the user to spend time in the NBS

laboratory to become familiar with their sources.

99
Future Directions

NBS will continue to investigate and develop new types of radiometric

sources as well as providing calibrations for sources to be used in

space experiments. Work on early models of portable low-powered (15w)

re-excited dimer lamps has shown that these lamps make good standards of

irradiance but are deficient as standards of radiance. Further work has

shown that changes in the lamp design can also produce a satisfactory

radiance standard. Lamps of advanced design incorporating NBS recommendations have been produced, and NBS calibrated one of them for use on the

FOS (faint object spectrograph) space shuttle experiment.

Another radiometric source NBS has been investigating and will

continue is an irradiance source of highly pure Lyman-a radiation which

does not utilize a monochromator. A preliminary report on this source was presented at the October 1982 annual meeting of the Optical Society

of America and a detailed manuscript is being prepared for publication.

NBS is presently involved in selecting and calibrating a deuterium

lamp to be flown on the SUSIM (solar ultraviolet spectral irradiance

monitor) space shuttle experiment as an in-flight calibration source.

Investigations are underway on a new source to provide radiometric

calibrations in the 20 nm-200 nm range. This source is a pulsed plasma

created by a focused laser beam striking a heavy metal target. A target

chamber is in operation, and initial measurements have been made with a grazing incidence spectrograph.

Contact Person at NBS

Wol fgang Wiese

Atomic and Plasma Radiation Division

301-921-2071

i

100
PHOTOMETRIC STANDARDS (7.7)

Description of Services

Calibration services in this area provide access to the photometric

scales realized and maintained at NBS. Lamp standards of luminous

intensity, luminous flux, and color temperature as described below are issued on a routine basis.

(a) Luminous intensity standards.

100-W (90-140 cd), 500-W (approximately 700 cd) and 1000-W

(approximately 1400 cd) tungsten filament lamps with C-13B

filaments in inside-frosted bulbs and medium bipost bases are supplied by NBS calibrated at either a set current or a specified color temperature in the range 2700-3000 K. Approximate uncertainties are 2 percent relative to the SI

unit of luminous intensity and 1.5 percent relative to NBS

standards.

(b) Luminous flux standards (geometrically total).

25-W vacuum tungsten lamps and 60- , 100- , 200- , and 500-W gas

filled tungsten lamps submitted by customers are calibrated.

Lamps must be base-up burning and rated at 120 V. Approximate

uncertainties are 2.5 percent relative to SI units and 1.5

percent relative to NBS standards.

Luminous flux standards for miniature lamps producing 6-400 lm are calibrated with uncertainties of 3 percent.

(c) Color temperature standards.

Airway beacon 500 W medium bipost lamps are calibrated for

color temperature in the range 2000-3000 K with an uncertainty

of 10 degrees.

Documentati on

Photometric Calibration Procedures, V. I. Burns and D. A. McSparron,

Natl. Bur. Stand. (U.S.), Tech. Note 594-3 (U.S. Government Printing

Office, Washington, DC, Nov. 1972).

Training Programs

At the present time, no training programs are offered by NBS.

Future Directions

In October 1979, an international redefinition of the photometric

unit system was adopted. The new definition replaced the previous

platinum point blackbody definition with a defined coupling constant to

the radiometric watt. This allows a variety of technically competitive

approaches to the realization of photometric scales. At present the NBS

101
photometric scales are based on the NBS scale of spectral irradiance.

Present photometric research centers on utilizing silicon selfcalibration techniques and filter radiometry realize photometric scales.

Future work will include an investigation of the possibility of replacing

some of the present lamp standards with photopically corrected silicon

cells and the radiometric characterization of new, spectral ly-rich

lamps.

Contact Person at NBS:

Donald McSparron

Radiometric Physics Division

301- 921-3613

102
SPECTROPHOTOMETRIC STANDARDS (7.8)

Description of Services

NBS provides standards of spectral transmittance for checking the

photometric scale of spectrophotometers. These are either 30 mm polished glass disks or 51 mm polished glass squares, 2 to 3 mm thick,

designated as cobalt blue, copper green, carbon yellow, and selenium

orange (disks will be supplied unless otherwise specified). Information

provided to user includes: (1) values of transmittance at 25 °C at

certain wavelengths from 390 to 750 nm, (2) the estimated uncertainty of

each value, and (3) the effect of temperature change on transmittance at

each wavelength. Holmium oxide glass standards are available for

checking the ultraviolet and visible wavelength calibrations of recording

spectrophotometers having a bandpass less than 2 nm. These are made of

polished Corning 3130 glass, 51 x 51 mm, 2.5 mm thick. A table of

wavelengths of minimum transmittance is provided in the report to the

user.

Measurements of spectral transmittance can be made for the wavelength

region 0.19 to 2.5 pm. Measurements of absolute spectral reflectance

factors, and spectral specular reflectance, can be made for the wavelength

region 0.25 to 2.5 pm. However, arrangements for these measurements on submitted specimens must be made before shipment of specimens. The

decision to perform the measurements and the instruments to be used will

rest with NBS and refusal may be made after inspection of the specimens.

Specimens not accepted for measurement will be returned. Accuracy and

precision estimates will be given, dependent upon the optical characteristics

of the submitted specimens.

Calibrated standards of didymium glass, for checking the wavelength

scale of spectrophotometers from 400 to 750 nm, are available as SRMs

2009, 2010, 2013, and 2014.

Calibrated standards for diffuse spectra reflectance are available

as SRMs 2015-16 (400-750 nm) and SRMs 2019-22 (250-2500 nm).

Calibrated standards for specular reflectance are available as SRMs

2003a (first surface mirror, 250-2500 nm) and SRMs 2023-25 (second

surface mirror, 250-2500 nm).

Documentation

Permanence of Glass Standards of Spectral Transmittance, K. S. Gibson

and M. A. Belknap, J. Res. Natl. Bur. Stand. (U.S.), (Research Paper

RP2093) , 44, 463 (May 1950).

New Reference Spectrophotometer, K. D. Mielenz, K. L. Eckerle, R. P. Madden, and J. Reader, Appl . Opt., 12, No. 7, 1630 (July 1973).

Establishing a Scale of Directional-Hemispherical Reflectance Factor 1: The Van den Akker Method, W. H. Venable, Jr. , J. J. Hsia, and V. R. Weidner, J. Res. Natl. Bur. Stand. (U.S.), 82, No. 1, 29 (July-Aug.

1977).

103
NBS 45°/Normal Ref lectometer for Absolute Reflectance Factors, J. J. Hsia and V. R. Weidner, Metrologia, 17, 97-102 (1981).

NBS Specular Reflectometer-Spectrophotometer, V. R. Weidner and J. J. Hsia, Appl . Opt., 19, 1268 (Apr. 1980).

New Reference Retroreflectometer, K. L. Eckerle, J. J. Hsia, V. R. Weidner, and W. H. Venable, Jr., Appl. Opt., 19(8), 1253 (1980).

Proposed Standards for the NBS Retroreflection MAP, K. L. Eckerle and J

J. Hsia, Color Res. and Appl., 7(3), 235 (1982).

Photometry and Colorimetry of Retroreflection: State-of-Measurement

Accuracy Report, K. L. Eckerle, Natl. Bur. Stand. (U.S.), Tech. Note

1125, 44 pages, (July 1980).

Extension of a Reference Spectrophotometer into the Near Infrared, K. L Eckerle, V. R. Weidner, J. J. Hsia, and Z. W. Chao, Natl. Bur. Stand.

(U.S.), Tech. Note 1175, 29 pages (Apr. 1983).

Measurement Assurance Program Transmittance Standards for Spectrophotometric Linearity Testing: Preparation and Calibration, K. L. Eckerle,

V. R. Weidner, J. J. Hsia, and K. Kafadar, J. Res. Natl. Bur.

Stand. (U.S.), 88(1), 25-36 (1983).

Second-Surface Mirror Standards of Spectral Specular Reflectance (SRMs

2023, 2024, 2025), J. C. Richmond, J. J. Hsia, V. R. Weidner, and D. B. Wilmering, Natl. Bur. Stand. (U.S.), Spec. Publ. 260-79, 31 pages (Oct.

1982).

White Opal Glass Diffuse Spectral Reflectance Standards for the Visible

Spectrum (SRMs 2015 and 2016), V. R. Weidner, Natl. Bur. Stand. (U.S.),

Spec. Publ. 260-82, 21 pages (1983).

Inverse-Fourth Apparatus for Photometric Calibrations, D. A. Swyt and J

G. LaRock, Rev. Sci. Instrum., 49(8), 1083 (Aug. 1978).

Training Programs

At the present time, no training programs are offered by NBS.

Future Directions

Studies and pilot runs on the Measurement Assurance Program (MAP)

transport standards for retroreflection, transmission, and diffuse

reflection have been completed. Plans are underway to establish MAP

services.

104
A long wavelength infrared spectrophotometry project has been

started to establish IR measurement capabilities from 2.5 to 25 pm on transmittance, diffuse reflectance and specular reflectance.

A new effort in fluorescence was initiated to establish measurement

capability and issue standards in this area.

Research efforts to develop high optical density standards (up to

optical density of 5.8) and to base calibration of master standards on the Inverse Fourth Apparatus (see above reference) is continuing.

Contact Person at NBS

Jack J. Hsia

Radiometric Physics Division

301-921-2791

105
PRESSURE AND VACUUM MEASUREMENTS (7.9)

Description of Services

The NBS provides measurement services for the calibration of piston

gages and transducers operating with gas in the range of 1.4 kPa to 4.2

MPa and with oil in the range of 700 kPa to 700 MPa. Calibrations are done by the cross-floating technique using NBS piston gages.

Type of Instrument

Gas-operated PG

Oil -operated PG

Oil -operated PG

Oil-operated PG

Range

1.4 kPa to 4 MPa

700 kPa to 280 MPa

40 to 400 MPa

70 to 700 MPa

Uncertai nty

±50 ppm

±60 ppm

±100 ppm

±200 ppm

Service for the calibration of pressure and vacuum gages, includes

capacitance-diaphragm gages, ball gages, and ionization gages ranging

from 100 pPa to 0.1 MPa. Spinning rotor gages will also be accepted for

special tests in this same range. In the range 1 Pa to 0.1 MPa the NBS

Ultrasonic Interferometer Manometer is the standard against which other

gages are calibrated. Its stability is 10-2 Pa plus 2 ppm of the

reading, and its inaccuracy is presently limited to 100 ppm by the

uncertainty in the speed of sound in the mercury used in the manometer.

In the range of 100 pPa to 10-2 Pa an NBS facility using a known flow

rate through a calculated conductance defines the pressure with an inaccuracy of 1%.

Documentation

Reduction of Data for Piston Gage Measurement, Natl. Bur. Stand (U.S.),

Monogr. 65 (1963).

Piston Gages, P. L. M. Heydemann and B. E. Welch, Chapter 4 in

Experimental Thermodynamics, Vol . II. Experimental Thermodynamics of

Non-Reacting Fluids, B. Le Neindre and B. Vodar, Eds., Part 3, 147-202

(Butterworth and Co. , London, England, 1975).

An Intercomparison of Pressure Standards Between LNE and NBS, R. G. Driver, J. C. Houck and B. E. Welch, J. Res. Natl. Bur. Stand. (U.S),

86, No. 3 (May- June 1981).

Absolute High Pressure Measurements, V. E. Bean, High Pressure Science

and Technology, B. Vodar and Ph. Mardeau, editors (Pergamon Press,

Oxford, England, 1980), p. 231.

An Intercomparison of Pressure Standards Between IMGC and NBS, J. C. Houck, G. F. Molinar, and R. Maghenzani , J. Res. Natl. Bur. Stand.

(U.S.), 88, 253 (1983).

106
Ultrasonic Interferometer Manometers: 10~5 Torr Resolution, P. L. M. Heydemann, C. Tilford, and W. Angel, Proceedings of 22nd International

Instrumentation Symposium, San Diego, CA, May 25-27, 1976.

Ultrasonic Manometers for Low and Medium Vacua Under Development at NBS,

P. L. M. Heydemann, C. R. Tilford and R. W. Hyland, J. Vac. Sci.

Technol . , 14, 597 (Jan. -Feb. 1977).

Nitrogen Sensitivities of a Sample of Commercial Hot Cathods Ionization

Gage Tubes, C. H. Tilford, J. Vac. Sci. Technol., 18, 994 (1981).

Sensitivity of Commercial Ion Gage Tubes, C. R. Tilford, Proceedings of

the 9th Symposium on Engineering Problems of Fusion Research (Institute

of Electrical and Electronics Engineers, Inc., New York, 1981), pp.

1924-1927. (Symposium held in Chicago, IL, 10/26-29/81.)

Performance Characteristics of a Broad Range Ionization Gage Tube, C. R. Tilford, K. E. McCulloh and H. S. Woong, J. Vac. Sci. Technol., 20, 1140

(1982).

Reliability of High Vacuum Measurements, C. R. Tilford, J. Vac. Sci.

Technol., Al(2), 152-162 (Apr. -June 1983).

Calibration of Molecular Drag Vacuum Gages, K. E. McCulloh, J. Vac. Sci.

Technol. Al(2) (Apr. -June 1983).

Training Programs

Twice per year NBS offers a 2-day Precision Pressure Seminar on the

operation and calibration of piston gages. An initial training course

on spinning rotor gages and ion gage calibration will be held in the

spring of 1984. As the calibration experience with these gages expands

and their limits and potential are better understood, the extent of such

courses will be expanded.

Future Directions

NBS is agressively assessing the accuracy of all piston gage

calibrations with the view of reducing the inaccuracy and documenting

it. This will take 3 years to complete the whole range. In FY 85 we expect to reduce the uncertainty in the gas-operated piston gage

calibration service in the range below 4 MPa and to complete the

documentation of such. In subseguent years we expect to reduce the

uncertainty at higher pressures by the development and careful

characterization of new primary pressure standards. Included in this

program is the extension of the range of the gas calibration service at

25 MPa.

There is presently a gap in the calibration service between 10- 2 to

1 Pa which will ultimately be closed by an oil interference manometer

and a modified flow apparatus. An effort is currently underway to

decrease the low pressure limit with a goal of reaching at least 10-

Pa. Leak calibration facilities are also being developed that will

107
range between 10-5 and 10-9 Pa m

3 /sec or lower. New documentation is

planned that will describe the results obtained in calibrating a conventional thi ode- ionization gage, a high vacuum standard, and the

update of the ultrasonic interference monometer.

Contact Person at NBS

Robert Soulen

Temperature and Pressure Division

301-921-3315

108
NEUTRON SOURCES AND DOSIMETRY STANDARDIZATION (8.1)

Description of Services

The NBS provides calibration services for natural standard neutron

sources and neutron measuring devices, i.e., dosimeters and activation

foi Is.

Neutron sources in the range from 5.0 x 10 5 to 5.0 x 109

neutrons/second may be calibrated to an accuracy of about ±1.2% (one

sigma) depending upon the amount and knowledge of construction of their

encapsulations. Emission rates (neutrons/second) of neutron sources of

unknown source strength are determined by the manganous Sulfate Bath

Method. The neutron sources are calibrated by comparing their strengths

to that of the NBS primary standard source, a Ra-Be photoneutron source known as NBS-1. The comparison of the source strengths is made by

activating a manganese sulfate bath solution and continuously counting

the induced, saturated manganese-56 radioactivity with a scintillation

counter. The present emission rate of NBS-1, which is absolutely

determined, is 1.246E+06 neutrons/second with an assigned uncertainty of

±0.9% (one sigma).

A wide variety of neutron radiation detection instrumentation

exists for the protection of personnel. NBS maintains a relatively wide

variety of neutron fields for both research and calibration in the area

of personnel dosimetry.

A thermal neutron beam is available at the thermal column of the

NBS Research Reactor (NBSR) which can provide dose equivalent rates up

to approximately 1 rem/hour over a 30 cm diameter circle.

Three monoenergeti c epithermal neutron beams are available at the

NBSR to determine neutron response as a function of energy:

These epithermal neutron beams give primarily neutron doses with the

gamma contributions being approximately 2 to 4%.

The neutron spectrum for a deuterium moderated Cf-252 is also

available for calibration of personnel dosimetry instruments and the

spectrum is very similar to that found inside containment of nuclear

reactors. Available rates are 1.1 x 10 5 n/cm2 *s) or equivalently 3.0

rem/hour. Additionally, a pure Df 252 fission neutron spectrum is

available with rates of 1.3 x 10 4 n/cm2 *s) or equivalently 1.6 rem/hour.

Materials dosimetry, such as that accomplished for surveillance of

fast neutron fluence seen by the pressure vessel in an operating nuclear

power plan, depends upon correct assay of the amount of isotopic

radioactivity induced in radiometric dosimeters, such as foils or wires.

NBS maintains Standard Fission Neutron Fields to supply calibration

2 KeV beam

24 KeV beam

144 KeV beam

Dose Equiv. = 4 mrem/hour

Dose Equiv. = 8 mrem/hour

Dose Equiv. = 70 mrem/hour

109
irradiations and Certified Fluence Standards. The NBS Cf-252 Fission

Neutron Source (typical maximum fluence 1.0 x 10 13 neutrons/cm2 in 24

hours) and the U-235 Cavity Fission Neutron Source (typical maximum

fluence 2.0 x 10 15 neutrons/cm2 in 24 hours) provide standard neutron

field spectra. Known fluences are based upon known source strengths for

the californium sources.

Documentation

Neutron Source Calibrations at NBS for Calibration Checks of Neutron

Radiation Instruments, V. Spiegel, Proc. of Symposium on Measurements

for the Safe Use of Radiation, Natl. Bur. Stand (U.S.), Spec. Publ. 456,

87 (Nov. 1976).

The Effective Half-Life of Californium-252, V. Spiegel, Jr., Nuclear

Science and Engineering, 53, 326 (1974).

Calibration of Thermal Neutron Absorption in Cylindrical and Spherical

Neutron Sources, V. Spiegel, Jr. and W. M. Murphey, Metrologia, 7, 34

(Jan. 1971).

Review of Measurements of Absolute Neutron Emission Rates and Spectra

from Neutron Sources, R. S. Caswell, Neutron Sources and Applications , Proc. ANS Natl. Topical Meeting, April 19-21, 1971, Augusta, GA.

C0NF-71042, Vol . I, 1-53 (1971).

The Correction Factor for Fast Neutron Reactions on Sulphur and Oxygen

in the Manganous-Sulfate-Bath Calibration of Neutron Sources, W. M. Murphey, Nucl. Instrum. Methods, 37, 13-21 (1965).

Recent Developments in Neutron Source Standardization, R. S. Caswell, R. H. Noyce, S. B. Garfinkel and E. R. Mosburg, Jr. , Neutron Dosimetry II , 547, IAEA, Vienna (1963).

Absolute Calibration of the National Bureau of Standards Photoneutron

Source: III. Absorption in a Heavy Water Solution of Manganous Sulfate,

R. H. Noyce, E. R. Mosburg, Jr., S. B. Garfinkel, and R. S. Caswell, J. Nucl. Eng., 17, No. 7, 313 -319 (1963).

Absolute Calibration of the National Bureau of Standards Photoneutron

Standard: II. Absorption in Manganese Sulfate, J. A. DeJuren and J. Chin, J. Res. Natl. Bur. Stand. (U.S.), 55, 311 (Dec. 1955).

Absolute Calibration of the National Bureau of Standards Photoneutron

Standard: I. , J. A. DeJuren, D. W. Padgett, and L. F. Curtiss, J. Res.

Natl. Bur. Stand. (U.S.), 55, 63 (Aug. 1955).

Reproducibility of Photo-Neutron Standards, L. F. Curtiss and A. Carson,

Phys. Rev., 76, 1412 (1949).

User's Manual --Neutron Calibration Fields at NBS, J. E. Hoy and R. B. Schwartz, Dec. 8, 1976. Revised by R. B. Schwartz (Jan. 1979).

110
Calibration and Use of Filtered Beams, R. B. Schwartz, Proc. International Specialists Symp. on Neutron Standards and Applications,

Gaithersburg, MD, Mar. 28-31, 1977, Natl. Bur. Stand. (U.S.), Spec.

Publ . 493, 250 (Oct. 1977).

The Design and Construction of a D2 0-Moderated 252 Cf Source for

Calibrating Neutron Personnel Dosimeters Used at Nuclear Power

Reactors, R. B. Schwartz and C. M. Eisenhauer, NUREG/CR-1204 (Jan.

1980).

Measurement of Neutrons Reflected from the Surfaces of a Calibration

Room, C. M. Eisenhauer, R. B. Schwartz, and T. Johnson, Health Physics,

42, 489-495 (1982).

Fission Cross-Section Measurements in Reactor Physics and Dosimetry

Benchmarks, J. A. Grundl and D. M. Gilliam, ANS Trans., 44, 533 (June

1983).

Integral Reaction Rate Measurements in 252 Cf and 235 U Fission Spectra,

G. P. Lamaze, E. D. McGarry, Proc. Conf. on Nuclear Data for Science and

Technology, Antwerp, Belgium (Sept. 1982).

Requirements for Reference Reactor Pressure Vessel Surveillance

Dosimetry to Benchmark Neutron Fields, E. D. McGarry, Proc. IAEA

Advisory Group Meeting on Nuclear Data for Radiation Damage Assessment

and Reactor Safety Aspects (Oct. 1981).

Measurement of the Average Activation Cross Section for the Reaction

63 Cu(n, a) 60 Co in the Spontaneous Fission Neutron Field of Californium-252,

C. Winkler, V. Spiegel, C. M. Eisenhauer, D. L. Smith, Nucl. Sci. &

Eng., 78, 415 (Aug. 1981).

National Standards for Neutron Measurements, J. Grundl, Traceability for

Ionizing Radiation Measurement Symposium, NBS (May 1980).

235 U Cavity Fission Neutron Field Calibration via the 252 Cf Spontaneous

Fission Neutron Field, V. Spiegel, C. M. Eisenhauer, D. M. Gilliam, J. A. Grundl, E. D. McGarry, I. G. Schroder, W. E. Slater, and R. S. Schwartz, IAEA Consultant's Mtg. on Neutron Source Properties, Debrecen,

Hungary (Mar. 1980).

Detailed Error Analysis of Average Fission Cross-Section Measurements in

NBS Standard Neutron Fields, J. J. Wagschal , R. E. Maerker (ORNL), and

D. M. Gilliam (NBS), Trans. Am. Nucl. Soc. , 33, 823 (Nov. 1979).

Dosimetry Results for BIG TEN and Related Benchmarks, D. M. Gilliam, J. A. Grundl, and C. E. Hansen, Third ASTM-EURATOM Symposium on Reactor

Dosimetry, Ispra, Italy (Oct. 1979).

Benchmark Referencing of Neutron Dosimetry Measurements, C. M. Eisenhauer,

J. A. Grundl, D. M. Gilliam, E. D. McGarry, and V. Speigel, Third

ASTM-EURATOM Symposium on Reactor Dosimetry, Ispra, Italy (Oct. 1979).

Ill
Covariance of Fission-Integral Measurements at the NBS 252 Cf and ISNF

Facilities and at the ORNL-PCA Facility, J. J. Wagschal , R. E. Maerker,

and D. M. Gilliam, Third ASTM-EURATOM Symposium on Reactor Dosimetry,

Ispra, Italy (Oct. 1979).

Neutronic Analysis of the NBS Intermediate-Energy Standard Neutron Field

(ISNF), P. D. Soran, R. J. Labauve, and D. C. George (LASL) and C. M. Eisenhauer (NBS), Trans. Am. Nucl. Soc. , 32 (June 1979).

Compendium of Benchmark and Test Region Neutron Fields for Pressure

Vessel Irradiation Surveillance; Standard Neutron Spectra-Part I: 252 Cf

Spontaneous Fission and Part II: 235 U Thermal-Neutron-Induced Fission,

Light-Water-Reactor, Pressure-Vessel -Survei 11 ance Dosimetry Progress

Report. U.S. Nuclear Regulatory Commission Document NUREG/CR-0551,

July-Sept. 1978 (Dec. 1978).

Reaction Rate Measurements and Integral Cross Sections Using the NBS

252 Cf Fission Neutron Indoor Irradiation Facility, V. Spiegel, C. M. Eisenhauer, and J. A. Grundl (NBS), and G. C. Martin, Jr. (GE). Second

ASTM-EURATOM Symposium on Reactor Dosimetry, Palo Alto, CA (Oct. 1977).

NUREG/CP0004 , Vol . 2, 959-967 (1978).

Utilization of Standard and Reference Neutron Fields at NBS, C. M. Eisenhauer, D. M. Gilliam, J. A. Grundl, and V. Spiegel. Second

ASTM-EURATOM Symposium on Reactor Dosimetry, Palo Alto, CA (Oct. 1977).

NUREG/CP0004, Vol. 3, 1177-1191 (1978).

A Californium-252 Fission Spectrum Irradiation Facility for Neutron

Reaction Rate Measurements, J. A. Grundl, V. Spiegel, C. M. Eisenhauer,

H. T. Fleaton, II, and D. M. Gilliam (NBS), and J. Bigelow (ORNL), Nucl.

Tech. , 32, 315 (Mar. 1977).

Fission Reaction Rate Standards and Applications, J. Grundl and C. Eisenhauer, International Symposium on Neutron Standards and

Applications, Gaithersburg, MD, Mar. 28-31, 1977, Natl. Bur. Stand.

(U.S.), Spec. Publ . 493, 156 (Oct. 1977).

Integral Measurements Results in Standard Fields, D. M. Gilliam,

International Symposium on Neutron Standards and Applications,

Gaithersburg, MD, Mar. 28-31, 1977, Natl. Bur. Stand. (U.S.), Spec.

Publ. 493 (Oct. 1977).

Neutron Transport Calculations for the Intermediate-Energy Standard

Neutron Field (ISNF), C. M. Eisenhauer and J. A. Grundl,

International Symposium on Neutron Standards and Applications,

Gaithersburg, MD, Mar. 28-31, 1977, Natl. Bur. Stand. (U.S.), Spec.

Publ. 493 (Oct. 1977).

Benchmark Neutron Fields for Reactor Dosimetry, J. A. Grundl and C. M. Eisenhauer, IAEA Consultants' Meeting on Integral Cross Section

Measurements in Standard Neutron Fields for Reactor Neutron Dosimetry,

Vienna (Nov. 1975-6).

112
Training Programs

None.

Future Directions

In the area of neutron source strength, measurement efforts will

focus on two major areas:

(1) Improve Accuracy: Work on factors which dominate present

accuracy limits. These are the uncertainty of 0.9% on the absolute

calibration of NBS-1 and uncertainties involved with comparing the

strength of sources whose emission rates differ by the factor of 5000.

(2) Facilities Upgrade : Improve performance of electronic and

mechanical equipment. Emphasis is on improved Health Physics procedures

to include new shielding and remote handling necessitated by increased

requests for calibrations of sources in the higher ranges and automation

of data acquisition and analysis.

In the area of neutron dosimetry calibrations and standards, plans

are being made to:

(1) Develop and distribute selected isotopic dosimetry reactions

as SRM certified fluence standards.

(2) Irradiate user's dosimetry foils to produce either certified

fluence or certified-fission standards.

(3) Perform high accuracy (± 1% to ± 3%) integral cross section

measurements of select dosimetry reactions in one or all of the NBS

standard fields.

(4) Perform spectrometer calibrations in Cf-252 fields.

In the area of neutron source measurements, the most substantive

documentation is over 15 years old and should be critically reviewed in

light of more recent and precise measurements. For example, the

consistency of NBS-1 absolute source strength with Cf-252 v measurements

could be studied or a reanalysis made of the uncertainty in the NBS-1

source strength. Plans are underway to prepare NBS reports on manganous

sulfate bath facility and equipment for neutron source comparisons and

on NBS-1 absolute source strength. Planned documentation in the

personnel dosimetry area include "Procedures for Calibrating Neutron

Personnel Dosimeters" and "Experimental Verification of the Neutron

Spectrum for the NBS D 2 Moderated 252 Cf Sources." In the area of

dosimetry calibrations and standards, a review paper on the state of

development of thermal and fission neutron standard fields at NBS is

planned.

113
Contact Person at NBS

Emmert McGarry

Nuclear Radiation Division

301- 921-2421

114
RADIOACTIVITY CALIBRATIONS (8.2)

Description of Calibration Services

Radioactivity calibration services are available from NBS as one part of a total program effort to disseminate accurate radionuclide

activity and emission rate calibrations. In general, it is more efficient to produce a batch of standards - sometimes Standard Reference

Materials (SRMs) - and encourage/recommend the measurement community to

utilize them as part of a calibration program rather than measure

individual samples submitted for calibration.

Radioactivity calibration services for some fifty radionuclides are available, including alpha-particle solid sources, beta-particle solutions

and gamma- ray solutions. In addition, some sources may be calibrated

under special arrangements on an "at cost" basis. In order to offer

such a broad range of services, NBS must place stringent limitations on the physical and chemical form and activity range of sources which can

be accepted. To ensure that these specifications are understood it is

essential that there be good communication between the technical

personnel at the user facility and those at NBS. A list of contacts at

NBS for five different types of calibrations are provided at the end of

this section. When planning to have a source calibrated, the user should discuss the following points with the contact at NBS:

o Type of calibration and units used for reporting results

Often, more than one type of calibration is available for a given source. Units to be used in reporting the result and some estimate of the total uncertainty in the calibration

should also be discussed.

o Source preparation, packaging, and shipment

Two general requirements apply to all sources submitted for

calibration: (1) All shipments must conform to applicable NRC

and DOT regulations for packaging and transport, and (2)

source description, including approximate activity, must be

provided in advance. The NBS Health Physics Section must

approve in advance all proposed calibrations, and sources may

be refused if the necessary information is not available.

o Reports of calibration

A typical NBS Report of Calibration is sent on completion of a radioactivity calibration service. If the user has particular

requirements for documentation of the calibration, these

should be discussed with the contact at NBS before the services

are performed.

Alpha-particle sources may be calibrated using the NBS 2 nu proportional counter 0.8 not defined-sol id-angle counter. The former

calibration is in terms of alpha-particle-emission rate into 2 n

115
steradians, while the1 latter is in terms of total activity. Thin

alpha-particle sources less than 10 cm in diameter and with activities

from 40 pCi to 300 nCi can be calibrated as to emission rate into the

forward hemisphere with an uncertainty of about 1.5 percent. Similar sources less than 1.6 cm diameter with activities between 5 nCi and 300

nCi can be calibrated for activity with an uncertainty of about 1.0

percent.

Solutions of eight radionuclides emitting only beta particles, with

activity concentrations of from 0.5 to 50 pCi/ml, can be measured with

an uncertainty 1.5 to 3.0 percent. However, the infrequent demand for

this service suggests that it be removed from the scheduled service.

Solutions of 26 radionuclides with half-lives greater than 15 days

and 13 with half-lives less than 15 days can be measured in properly

filled NBS ampoules with the calibrated NBS "4 7t" gamma-ray ionization

chambers. Uncertainties vary from 0.8 to 3.4 percent; activity limits are between 10 and 1500 pCi , depending on the radionuclide.

Sources which do not meet the specifications for the NBS scheduled

calibrations may be calibrated on an "at cost" basis. In such instances

a complete description of the source and the nature of the calibration

must first be provided in writing to NBS. Such services are usually

expensive because custom preparations and calibrations require additional

labor for experimental design and measurements, and these expenses must

be recovered. Often, it is more economical to have a commercial laboratory

prepare a source which meets the specifications for a scheduled

calibration, and have the source forwarded to NBS.

Calibration and measurement services can be provided for appropriate

gaseous samples of tritium and carbon-14 as well as a number of gamma-rayemitting noble-gas radionuclides. The preferred sample containers for

the assay of gamma-ray emitters are 5 cm3 ampoule or a flame-sealed 32.5 cm3 sphere. It is desirable to have the material cryogenical ly transferred

into the sphere, followed by flame sealing. If this is not possible, a "flow-through" container can be used. The activity level and the

composition and pressure of the carrier gases are important considerations

which should be discussed with the technical contact at NBS. Gamma-ray

point sources (less than 1 cm diameter) and solution sources containing

gamma-ray-emitting radionuclides may be assayed with calibrated Ge(Li)

spectrometers.

Documentati on

An Experimental Study of the Backscatteri ng of 5.3 MeV-Alpha Particles

from Platinum and Monel Metal, D. H. Walker, Int. J. Appl . Radiat.

Isotopes, 16, 183 (1965).

Backscatteri ng of Alpha Particles from Thick Metal Backings as a Function of Atomic Weight, J. M. R. Hutchinson, C. R. Naas, D. H. Walker, and W. B. Mann, Int. J. Appl. Radiat. Isotopes, 19, 517 (1968).

NCRP Report 58, A Handbook of Radioactivity Measurements Procedures,

Section 3.7-Alpha Particle Counting, W. B. Mann (ed.), National Council

on Radiation Protection and Measurements, Washington, DC (1978).

116
Study of the Scattering Correction for Thick Uranium-Oxide and Other

a-Particle Sources-I: Theoretical, L. L. Lucas and J. M. R. Hutchinson,

Int. J. Appl. Radiat. Isotopes, 27, 35 (1976).

Study of the Scattering Correction for Thick Uranium-Oxide and Other

a-Particle Sources-II: Experimental, J. M. R. Hutchinson, L. L. Lucas,

and P. A. Mullen, Int. J. Appl. Radiat. Isotopes, 27, 43 (1976).

Radioactivity Standards of the Noble Gases, W. B. Mann, F. J. Schima,

and M. P. Unterweger, Proceedings of Noble Gases Symposium, Las Vegas

(1978), p. 144, R. E. Stanley and A. A. Moghissi (eds.), ERDA TIC

C0NF730915.

Calibration of Ge(Li) Gamma-Ray Spectrometers for the Measurement of

Radioactive Noble Gases, B. M. Coursey, J. M. R. Hutchinson, and M. P. Unterweger, Int. J. Appl. Radiat. Isotopes, 28, 551 (1977).

Germanium Detector Efficiency Calibrations with NBS Standards, A. T. Hirshfeld, D. D. Hoppes, and F. J. Schima, p. 90 in Proc. ERDA X- and

Gamma-Ray Symp. , Ann Arbor, MI (1976).

Training Programs

There are currently no formalized training programs for radioactivity

calibrations. However, the agencies who control the use of radionuclides

in the U.S. have encouraged many suppliers of commercial standards and

radiopharmaceuticals to utilize NBS calibration services as well as participate in unscheduled measurement tests. The regulatory agencies

themselves are involved in measurement checks through interagency

agreements with NBS. The calibration services and unscheduled tests

provide one mechanism for traceability exercises which have evolved over

the past decade for radioactivity measurements. With minimal NBS or other laboratory expense, a continuing check of the quality of measure- ments for a variety of radionuclides is possible.

Future Directions

"A Handbook of Radioactivity Measurements Procedures" is now being

revised for republication as Report No. 58 of the National Council on Radiation Protection and Measurements. Valuable suggestions and data

for all types of radioactivity measurements will be included. Special

seminars on topics such as low-level-radioactivity or nuclear medicine

measurements are being planned with the cooperation of national or international organizations. With the encouragement of the regulatory

agencies, specific traceability requirements for commercial

radioactivity standards are being developed.

117
Contact Persons at NBS

Service NBS Contact

General information D. D. Hoppes

Nuclear Radiation

301-921-2668

Division

Alpha-particle solid sources P. A. Mullen 301-921-2383

Beta-parti cl e-emi tti ng radi o- nuclides in solutionB. M. Coursey 301-921-2383

Gamma- ray-emi tti ng radionucl ides

in solution by "47i"y ionization

chamber

J. M. Calhoun 301-921-2383

Calibration of gaseous radionuclides F. J. Schima

M. P. Unterweger

301-921-2396

Calibration of gamma- ray- emitting A. T. Hirshfeld 301-921-2652

radionuclides by gamma- ray spectrometry

118
X-RAY AND GAMMA-RAY MEASURING INSTRUMENTS (8.3)

Description of Services

The NBS provides calibration services for x-ray and gamma-ray

measuring instruments, passive dosimeters and x-ray penetrameters.

X-ray calibration and irradiation is provided in 32 beam qualities,

varying from 10 kV to 300 kV constant generating potential, with halfvalue layers from 0.03 mm A1 to 23 mm A1 « 6 mm Cu. Gamma-ray calibration and irradiation is provided using cobalt-60 and cesium- 137 beams.

Calibration and irradiation can be provided at exposure rates appropriate

to either radiation-protection or radiation- therapy applications.

X-ray measuring instruments are calibrated in terms of exposure in an x-ray beam at a point where the exposure rate has been determined by

means of a standard free-air ionization chamber. In order to provide

instrument calibrations over a wider range of x-ray energies, many

combinations of generating potential and filtration are available.

Gamma-ray measuring instruments are calibrated in terms of exposure

or absorbed dose at points in the collimated cobalt-60 and cesium-137

gamma- ray beams that have been standardized by means of graphite cavity

chambers or a graphite calorimeter. Exposure rates and absorbed dose

rates at the time of calibration are computed from the original beam

standardization data and appropriate decay corrections.

Irradiation of passive dosimeters, for readout by the customer, are generally in terms of exposure; for passive dosimeters suitable for insertion in a phantom, irradiation in terms of absorbed dose can be provided by in-phantom irradiation using cobalt- 60 gamma rays.

X-ray penetrameters, of the Ardran-Crookes type, can be calibrated

using constant x-ray generating potentials up to 250 kV. These penetrameters are used for measurement of the generating potential of

diagnostic x-ray units.

Documentation

Exposure Spectra from the NBS Vertical -Beam 60 Co Gamma-Ray Source, M. Ehrlich and C. G. Soares, Natl. Bur. Stand. (U.S.), NBSIR 76-1117

(1976).

Spectrometry of a 60 Co Gamma-Ray Beam Used for Instrument Calibration,

M. Ehrlich, S. M. Seltzer, M. J. Bielefeld, and J. I. Trombka,

Metrologia, 12, 169 (1976).

The Graphite Calorimeter as a Standard of Absorbed Dose for Cobalt-60

Gamma Radiation, J. S. Pruitt, S. R. Domen, and R. Loevinger, J. Res.

Natl. Bur. Stand. (U.S.), 86, No. 5, 495-502 (1981).

The Photon-Fluence Scaling Theorem for Compton-Scattered Radiation, J. S. Pruitt and R. Loevinger, Medical Physics, 9, No. 2 (Mar. -Apr. 1982).

119
Uncertainty in the Delivery of Absorbed Dose, R. Loevinger and T. P. Loftus, Ionizing Radiation Metrology, International Course at Varenna,

Italy, 1974, E. Casnati , ed. , G-6, 459-473. Editrice Compositori,

Bologna, 1977.

Medical Dosimetry Standards Program of the National Bureau of Standards,

R. Loevinger. Proceedings of a Symposium on National and International

Standardization in Radiation Dosimetry, Atlanta, GA, Dec. 5-9, 1977

(International Atomic Energy Agency, Vienna, 1978). (This article

provides references for either publications on NBS exposure and absorbeddose standards.

Training Programs

None.

Future Directions

Efforts will focus on providing calibration and irradiation

services in terms of water absorbed dose for gamma-ray beams of

cobalt-60 and cesium-137.

Contact Person at NBS

Robert Loevinger

Radiation Physics Division

301-921-2364

120
GAMMA-RAY AND BETA-PARTICLE SOURCES (8.4)

Description of Services

Calibration services are provided for gamma- ray and beta-particle

sources submitted to NBS subject to specified conditions. A summary of

those conditions are listed below:

(a) Financial responsibility: Except for negligence by NBS

personnel, NBS assumes no responsibility for loss or damage to the

sources while in its possession.

(b) Period of measurement: Inquiry should be made as to

scheduling and turnaround time before the source is submitted.

(c) Preparation: Sources submitted for calibration must be sealed

so that there can be no escape of any radioactive material, including

any gaseous decay products. The sources, shielding, and packaging must

be free of contamination. Contaminated or leaking sources cannot be

measured and may cause considerable loss of time and damage to laboratory

facilities. Sources must have been sealed for a sufficient time to be

substantially in radioactive equilibrium with their decay products when

these contribute to the emitted radiation.

(d) Packaging for shipment: Packages must be in compliance with

the regulations of the Department of Transportation as detailed in CFR

Title 49 and the regulations of the Nuclear Regulatory Commission as detailed in CFR, Title 10, Part 71. Copies of the Codes are available

at the Government Printing Office, Washington, DC 20402.

All shipments to NBS of gamma-ray and beta-particle sources must be

in reusable containers. A drawing showing the source container and a description of the method of source removal must be provided before the

shipment is received at NBS.

(e) Possession of licensed materials: In submitting a source for

calibration, it is necessary for the submitter to certify that he is

duly authorized to possess the source under license by the applicable

authority. In the case of individuals residing in a State that has

entered into agreement with the Nuclear Regulatory Commission, State

regulations are applicable to all sources including radium. In the case

of other individuals, NRC regulations are applicable (radium is not

licensed by the NRC). This certification may be by letter, by a suitable statement on the purchase order covering the calibration fee, or by a clear copy of the submitter's Possession License for the source.

Gamma-ray sources of cobalt-60, cesium-137, iridium-192, and

iodine-125 are calibrated in terms of exposure rate at 1 m. Radium is

calibrated in terms of mass of equivalent radium content measured

relative to the National Radium Standard through comparison of the gamma

radiation from the specimen and the standard. Calibration in terms of

absorbed dose rate is provided for suitable encapsulated beta-particle

sources; the dose rate to a low-atomic-number material (plastic) is

determined by measurement with an extrapolation chamber.

121
Documentation

Medical Dosimetry Standards Program of the National Bureau of Standards,

R. Loevinger. Proceedings of a Symposium on National and International

Standardization in Radiation Dosimetry, Atlanta, GA, Dec. 5-9, 1977

(International Atomic Energy Agency, Vienna, 1978). (This article

provides references for earlier publications on NBS exposure and

absorbed-dose standards.)

Standardization of Iridium-192 Gamma-Ray Sources in Terms of Exposure,

T. P. Loftus , J. Res. Natl. Bur. Stand. (U.S.), 85, No. 1, 19-25 (1980).

Training Programs

None.

Future Directions

Plans are to maintain state-of-the-art measurement capability to

provide calibration services for gamma-ray and beta-particle sources.

Contact Person at NBS

Robert Loevinger

Radiation Physics Division

301-921-2364

122
DOSIMETRY OF HIGH-ENERGY ELECTRON BEAMS (8.5)

Description of Services

NBS provides dosimeters twice a year to users requesting assistance

with absorbed-dose measurements in high-energy electron beams. The

dosimeters consist of ferrous sulfate (Fricke) solution in radiationresistant silica-glass spectrophotometer cells. The user irradiates all

but one of the three furnished dosimeters to an absorbed dose between 50

and 80 Gy (5000 and 8000 rad) at electron energies between 5 and 50 MeV.

After irradiation, the dosimeters are returned to NBS for spectrophotometric evaluation of the ferric-ion concentration in terms of absorbed

dose in the phantom.

As a special service and by special arrangements, NBS provides

calibration services for ionization chambers. An ionization chamber and

electrometer combination, with the electrometer marked in terms of

exposure or absorbed dose, is calibrated by providing a dimensionless

correction factor for the electrometer scale. An ionization chamber

submitted without an electrometer is calibrated in terms of exposure or absorbed dose per unit charge. Ionization chambers are tested, prior to

calibration, for leakage, radiation- induced leakage, stabilization time,

short-term stability, recombination loss, connection to the atmosphere,

and guard-electrode insulation (if applicable). Chambers found un- suitable for calibration are returned with a statement of the reason for

rejecti on.

Documentation

Uniformity of High-Energy Electron-Beam Calibrations, M. Ehrlich and P. J. Lamperti , Phys. Med. Biol. 14, 305-314 (1969).

Training Programs

None.

Future Directions

It is expected that additional facilities will be available to

provide calibrations in electron and photon beams at energies up to 30

MeV.

Contact Person at NBS

Robert Loevinger

Radiation Physics Division

301-921-2364

123
DOSIMETRY FOR HIGH-DOSE APPLICATIONS (8.6)

Description of Services

NBS provides a variety of dosimeter calibration services to industrial

radiation users of intense radiation fields, in particular, large

gamma- ray sources and electron accelerators up to approximately 4 MeV.

The services include the administering of known absorbed doses of

ionized photons to customer-supplied dosimeters, supplying calibrated

secondary-standard transfer dosimeters to customers for irradiation and

subsequent readout and dose interpretation, and special measurement

services such as the determination of temperature dependence, dose-rate

dependency or reproducibility of dosimeter response, and measurement of

detailed dose distributions in specific irradiation geometries and in

selected absorbing materials. These dose distribution measurements can include dose profiles in heterogenous absorbers and at surfaces and

interfaces of different substances. Such information is important in

research leading to the commissioning of a radiation process, and in

measurement assurance that provides quality control of a given radiation

treatment.

Irradiation tests are available for customer-supplied dosimeters

(such as solid radiochromic or liquid chemical types) or test samples

that are sent to NBS, where they are packaged in appropriate material of

thickness sufficient to approximate conditions of electron equilibrium.

They are then irradiated in the NBS standard 60 Co calibration facility

to specific agreed-upon absorbed dose values in the nominal "high-dose"

range of 10- 106 grays (103 -108 rads). The dosimeters may either be read

and evaluated by NBS or sent back to the customer for their analysis and

evaluation. Each dosimeter should not exceed dimensions of 1 cm x 2 cm x 5 cm.

NBS can provide sets of calibrated radiochromic dosimeters packaged

in appropriate equilibrium material (such as polystyrene or aluminum).

The sealed packaged dosimeters are sent to the customer for irradiation

to nominal agreed-upon absorbed dose levels in a prescribed geometrical

arrangement. The unopened packaged dosimeters are then returned to NBS

to be read and evaluated. The absorbed dose range that is suitable for use with the radiochromic dosimeters is 1 to 600 kGy (0.1 to 60 Mrad) in

water, silicon, aluminum, graphite, or certain plastics.

Spectrophotometric analysis of irradiated dosimeters may be done at

several specific ultraviolet or visible optical wavelengths or as a spectral scan over an appropriate wavelength region of interest.

Documentation

A National Standardization Programme for High-Dose Measurements, W. L. McLaughlin, Technical Report No. 205, 17-32, IAEA, Vienna (1981).

Dosimetry for Industrial Radiation Processing, W. L. McLaughlin, J. C. Humphreys, and A. Miller, Natl. Bur. Stand. (U.S.), Spec. Publ. 609

(1981).

124
Dye Film Dosimetry for Radiation Processing, J. C. Humphreys and W. L. McLaughlin, IEEE Trans. Nucl. Sci., NS-28, No. 2, 1797-1801 (Apr. 1981).

The Measurement of Absorbed Dose and Dose Gradients, W. L. McLaughlin,

Radiat. Phys. Chem. , 15, 9-38 (1980).

Dosimetry Standards for Industrial Radiation Processing, W. L. McLaughlin, National and International Standardization of Radiation

Dosimetry, 1, IAEA, Vienna (1978).

Training Programs

None.

Future Directions

Work is going on to develop better dosimetry capabilities for

high-dose electron beams and for fast-pulse radiation sources. These

efforts include real-time readout multifoil calorimeter systems and new radiochromic dosimeters usable over a wide dose range.

Contact Person at NBS

William L. McLaughlin

Radiation Physics Division

301-921-2201

125

NBS MEASUREMENT SEMINARS

The primary objective of the NBS conducted seminars is to provide

advice and assistance on measurements and calibrations so that laboratories

outside NBS can make measurements consistent with national standards as maintained by NBS. Participation is open to a limited number of persons

from measurement and standards laboratories who meet appropriate prerequisites relating to education, work experience, and current professional

activity.

Each seminar lasts from one to five days and its meetings are devoted to lectures, group discussions, and laboratory demonstrations.

A course may be cancelled if registration is insufficient. However, in

the past, requests for enrollment have nearly always exceeded the

numbers that could be accommodated. Laboratory directors who wish to

have members of their staff attend any of these courses are therefore

urged to send, as soon as possible, a letter of application to the

individual named in the course descriptions below. Applications should

also be accompanied by a check, billing authorization, or purchase order

for the stated fee.

Acceptance of qualified applicants, on the basis of first come,

first served, other things being equal, will be made by letter not later

than 4 weeks prior to the scheduled date of the course. Detailed

information on schedules and housing will be available at that time.

Those accepted will be expected to study the assigned reading material

before coming to the course and should be prepared to discuss their own experiences with related problems.

o Quality Assurance of Chemical Measurements Seminar

Descri pti on : This two-day seminar is concerned with techniques to

improve the precision and accuracy of analytical measurements such as those needed in the compositional analysis of materials, process control,

and regulatory enforcement. It is designed for supervisors of analytical

laboratories, experienced analytical chemists, and those responsible for

the development and/or supervision of laboratory quality control programs.

Topics discussed will include: general aspects of quality assurance;

the role of Standard Reference Materials in quality assurance; statistical

considerations used in the evaluation of data quality; and good laboratory

practices for precise and accurate chemical measurements. In addition,

each participant may elect to attend three two-hour clinics on good

measurement practices, selected from the following areas: atomic absorption spectrometry; gas analysis; gas chromatography; gas chromatographymass spectrometry; general analytical chemistry; ICP spectroscopy; ion

chromatography; isotope dilution mass spectrometry; liquid chromatography;

polarography- voltammetry; neutron activation analysis; spectrophotometry;

statistical concepts; UV-IR organic spectroscopy; standard reference

materials; and quality assurance program development. Applicants should

indicate the three clinics of their choice when applying.

127
Arrangements : Attendance will be limited to 30. Fee : $300.

Dates : To be announced. For further information contact : Dr. John K. Taylor, Center for Analytical Chemistry, A309 Chemistry Building, NBS,

Washington, DC 20234. Telephone : 301-921-3497.

o Precision Thermometry Seminar

Description: The seminar will consist of integrated instruction in

platinum resistance thermometry, 1

i quid- in-glass thermometry, thermocouple

thermometry, and thermistor thermometry to be given over a five day

period. Material to be covered includes the International Practical

Temperature Scale of 1968; its use in the laboratory; thermometers and

instrumentation, including automatic data acquisition; the treatment of

calibration data; and innovations in thermometry. Time will be split

between lecture sessions and hands-on measurements in the laboratory.

The seminar is especially intended for calibration laboratory personnel

and others who wish to undertake precision temperature measurements.

Applicants should possess undergraduate training in physics or engineering

and should have some laboratory experience in metrology.

Arrangements : Attendance will be limited to 25. Fee : $300.

Dates: October 15-19, 1984. For further information contact : Nancye

E. McBryde or Robert J. Soulen, Temperature and Pressure Measurements

and Standards Division, NBS, Washington, DC 20234. Telephone : 301-921-3315.

o Frequency Measurements and Calibrations Seminar

Description : This seminar is intended for engineers and standards

lab technicians involved in frequency calibrations. The course will be

taught at a practical level to satisfy those new to the field as well as more experienced users. Methods taught will use commercial ly-avai lable

equipment. Topics to be covered:

Crystal Oscillator Calibration

Applications of Frequency Counters

How to Choose a Frequency Calibration Source

Care and Use of Frequency Sources

Using L0RAN-C and WWBV for Frequency Calibrations

Time and Frequency Measurement Assurance Services at NBS

Organization of Time and Frequency in the U.S.

NBS, USN0, and Other Publications

NOTE: Although all of the above subjects will be covered, emphasis will

be on making practical frequency calibrations and measurements.

Fee : To be announced. Dates : To be announced. For further

information contact: Mike Lombardi, Time and Frequency Division, NBS,

Boulder, CO 80303. Telephone : 303-497-3212.

128
0 Calibration and Use of Piston Gages Seminar

Description : The seminars are held to help industrial and other

users attain the highest possible accuracy in pressure measurements with

piston gages. The seminar is directed at engineers and senior

technicians. The two-day seminar presents information on the theory of

piston gages, elastic distortion, design and types, calibration of

controlled clearance piston gages, calibration by cross-float, error

analysis, computer programs, demonstration of cross-float, hydrostatic

weighing and transducer calibrations. The seminar closes with a tour of

the laboratory, and a discussion of research and development work in the

field of pressure measurements.

Arrangements : Attendance will be limited to 10-15. Fee : $150.

Dates : May 17-18, 1984 and November 15-16, 1984. For further

information contact : Bernard E. Welch or Nancye E. McBryde, Temperature

and Pressure Measurements and Standards Division, NBS, Washington, DC

20234. Telephone : 301-921-2121 or 3316.

o Frequency Standards and Clocks Seminar

Description : This seminar is intended for program managers,

planners, and systems engineers. Topics to be covered:

A History of Time Scales

National and International Structure of Time and Frequency

Concepts, Definitions, and Measures of Short-Term Frequency Stability

Techniques for Measuring Short-Term Frequency Stability and Noise in

Osci 1 1 ators

Review of Performance of Commercial Frequency Standards

Limitations of Present-Day Atomic Frequency Standards

Possible Advances in Future Clocks and Frequency Standards

The Process of Timekeeping (Clocks Modeling)

Time Coordination: Methods for Comparison of Time Scales

Propagation Effects on Radio Transmissions

Optical Techniques and Propagation Effects

Fee : $370. Date : August 1984 (Tentative). For further

information contact : Mike Lombardi, Time and Frequency Division, NBS,

Boulder, CO 80303. Telephone : 303-497-3212.

o Electrical Measurements Assurance Programs Seminar

Description : This five-day intensive seminar on measurement

quality assurance provides in-depth training for those involved in dc

and low frequency electrical measurements. Participants will receive

instruction on how to establish and maintain rigorous quality control

programs in their own laboratories to ensure the accuracy of electrical

measurements. The primary emphasis will be on quality control for dc

voltage metrology; the techniques used are readily applicable to otherelectrical measurement areas.

129
Each class day will consist of lectures, to be followed by ample

time for questions and answers and discussion of real measurement

problems. Reference materials will be provided. This seminar is

designed for technical personnel working in electrical measurements and

it is not recommended for entry-level people unless they have a background in electrical engineering or physics. Some college level

math is desirable, but attendees should, as a minimum, have a thorough

knowledge of high school algebra.

The first morning session will be devoted to a discussion of "why

have a measurement assurance program (MAP)," covering the costs and

benefits of such a program, the implications for traceability, the

impact on the operation of a calibration or standards lab, etc. Lab

managers and/or supervisors of attendees are invited to join the group

for this session. (Each attendee may invite one additional person to

attend the Monday morning session at no additional cost.)

Arrangements : Plans are in progress for seminars in Minneapolis,

Seattle, and Orlando. Attendance will be limited to 40. Fee : To be

announced. Dates : To be announced. For further information contact: Dr. Arthur 0. McCoubrey, Center for Basic Standards, Physics Building,

Room B160, Washington, DC 20234. Telephone : 301-921-3301.

130
NBS-114A [REV. 2-80

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See i nstructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 84-2875

2. Performing Organ. Report No. 3. Publication Date

May 1984

4. TITLE AND SUBTITLE

NBS Physical Measurement Services Status Report

5. AUTHOR(S)

Editors: Lottie T. McClendon and R. Keith Kirby

S. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State, ZIP)

10.

SUPPLEMENTARY NOTES

_ Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most sign i fi cant information. If document includes a si gn i fi cant bibliography or literature survey, mention it here)

This report describes the current status of NBS 1 s physical measurement services.

It describes each of these services under five sections: Description;

Documentation; Training Available; Future Directions; Contact Person at NBS.

The services are keyed to the numerical classification of NBS Special Publication

No. 250. This document will also serve as a source for the complete revision

of NBS SP 250 in the near future.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate - < < . '•••

calibrations NBS services } services 5 status report

13. AVAILABILITY 14. NO. OF

PRINTED PAGES

i Unlimited

jX~j For Official Distribution. Do Not Release to NTIS

1

1 Order From Superintendent of Documents, U.S. Government Printing Office, r. ash mgton , D.C. “ 20402. IS. Price

Order From National Technical Information Service (NTIS), Springfield, VA. 2216'

Otwnyt- C