NBSIR 76-1038

NBS InterAgency Transducer

Project

Progress Report No. 3

p. S. Lederer and J. S. Hilten

Electronic Technology Division

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

April 1976

Progress Report Covering Period January 1, 1975 to June 30, 1975

Prepared for

Naval Air Systems Command,

U. S. Navy, and Transducer Committee,

Telemetry Group,

Range Commanders Council

NBSIR 76-1038

NBS INTERAGENCY TRANSDUCER

PROJECT

PROGRESS REPORT NO. 3

p. S. Lederer and J. S. Hilten

Electronic Technology Division

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

April 15, 1976

Progress Report Covering Period January 1 , 1 975 to June 30, 1 975

This is a progress report. The work is incomplete and is continuing.

Results and conclusions are not necessarily those that will be included

in a final report. Performance test data were obtained from one or two

samples of several transducer types, and do not necessarily represent

the characteristics of all transducers of a given type.

Prepared for

Naval Air Systems Comnnand,

U. S. Navy, and Transducer Committee,

Telemetry Group,

Range Commanders Council

U.S. DEPARTMENT OF COMMERCE, Elliot L. Richard9on. Seentmry

James A. Baker, III, Under Secntary

Dr. Betey Ancker-Johnson. Assistant Saerataiy for Sciance and Taehnoiogy

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Acting Director

ABSTRACT

Concluding efforts related to the development of a test

method for evaluating the effects of short-duration, thermal

radiant-energy transients on pressure-transducer response

are described. The method consists of monitoring pressuretransducer output (zero shift with the transducer at atmospheric pressure) as the transducer is exposed to radiation

resulting from the ignition of a photographic flashbulb or

from the discharge of an electronic flash. Thermal energy

pulses as great as 0,1 J/cm^, with durations of about 6 ms,

have been generated using an electronic flash; pulses of up

to 2.2 J/cm^, with durations of about 37 ms , have been generated using No. 22 flashbulbs. Flood-flash FF-33 lamps

were also investigated, but their use is not recommended.

In tests with No. 22 bulbs, 25 commercial pressure transducers have shown zero shifts ranging from 0.k% to about

kOO% of the full-scale output. Transducer-related tasks

being performed for other agencies are also described briefly, and other recent NBS publications of interest to the

transducer community are identified.

Key words: Calibration; dynamic; electronic flash; photoflash bulb; pressure; pressure measurement;

pressure transducer; pressure transducer response; response; thermal transient; transducer; zero shift.

NBS InterAgency Transducer Project

Progress Report No. 3, for the Period

From January 1 to June 30, 1975

to the

Naval Air Systems Command,

U. S. Navy and Transducer Committee,

Telemetry Group,

Range Commanders Council

NBS Cost Center 4253^3^

Prepared by

Paul S. Lederer

and

John S . Hi 1 ten

ABSTRACT

Concluding efforts related to the development of a test method

for evaluating the effects of short-duration, thermal radiant-energy

transients on pressure-transducer response are described. The method

consists of monitoring pressure- t ransducer output (zero shift with

the transducer at atmospheric pressure) as the transducer is exposed

to radiation resulting from the ignition of a photographic flashbulb

or from the discharge of an electronic flash. Thermal energy pulses

as great as 0.1 J/cm^, with durations of about 6 ms , have been generated using an electronic flash; pulses of up to 2.2 J/cm^, with durations of about 37 ms , have been generated using No. 22 flashbulbs.

Flood-flash FF-33 lamps were also investigated, but their use is not

recommended. In tests with No. 22 bulbs, 25 commercial pressure transducers have shown zero shifts ranging from 0.^^ to about kOO% of the

ful 1-scale output.

Transducer-related tasks being performed for other agencies are

also described briefly, and other recent NBS publications of interest

to the transducer community are identified.

Key words: Calibration; dynamic; electronic flash; photoflash bulb;

pressure; pressure measurement; pressure transducer;

pressure transducer response; response; thermal transient;

transducer; zero shift.

1. INTRODUCTION

A brief background for the NBS InterAgency Transducer Project,

its recent history, and current objectives were given in a previous
-2-

progress report []]*. The current task assigned to the Project by

the Transducer Commi ttee^'f" calls for the development of a test method

for evaluating the effects of short-duration, thermal radiant-energy

transients on pressure-transducer response. The method is intended

to serve as an initial screening test.

Specific requirements set by the Transducer Committee and the

Naval Air Systems Command include: the method should be inexpensive

to implement and simple to operate; the equipment should be readily

replicable; and the method should be capable of applying thermal

transients with durations of 1 ms and longer with controlled heatflux inputs to the test transducers.

Work continued on the test method developed during earlier reporting periods [1,2]. The method consists of monitoring pressuretransducer output (zero shift with the transducer at atmospheric

pressure) as the transducer is exposed to radiation resulting from

the ignition of a photographic flashbulb or from the discharge of an

electronic flash.

The sponsors further intend that the method be used for evaluating

the effectiveness of various schemes that have been proposed to reduce

the effect of thermal radiant-energy transients on pressure-transducer

response. Experimental work for this new task will begin following the

completion of experimental development of the method. Preliminary work,

including a survey of protective schemes now in use, is discussed in

section k.

2. EXPERIMENTAL DEVELOPMENT

Experimental work carried out during this reporting period consisted of investigations of the effect of various parameters on the

method and evaluation of the flood-flash FF-33 lamps as a potential

source for the method.

The investigations include studies of such effects as: (l) the

supply-voltage variation on electronic-flash output, (2) the aperture

size on energy-meter reading, (3) the angle of incidence on transducer

response, (^) the presence of reflectors on transducer response, (5)

the energy loss in the glass window, (6) the increased air pressure

from heating, and (7) the exposure of the transducer to full-scale

pressure.

2.1 Effect of Supply-Voltage Variation on Electronic-Flash Output

Evaluation of the electronic-flash system as a source for the

method included investigation of the dependence of flash-system performance on supply voltage when the unit was operated from either the

a-c line or from a battery supply.

"Figures in brackets indicate literature references, section 7.

**Transducer Committee, Telemetry Group, Range Commanders Council.
-3-

To measure the effect of a-c line voltage variations on electronicflash energy output, a variable transformer was inserted Into the line

ahead of the internal flash power supply, and the radiant-energy output

was measured at selected a-c supply voltages ranging from 110 V to 120 V

in 1-M steps. The a-c supply voltage was set with the variable transformer and measured on a digital multimeter. The flash energy output

was measured with the energy meter and the photodlode; the corresponding

zero shift of transducer Z was also measured. Table 1 shows that the

radiant energy available at an a-c supply voltage of 110 V is about 10%

less than that at 120 V. The percentage change in radiant energy is on

the order of double the percentage change in supply voltage causing it.

This observation corroborates the recommendation that some type of voltage regulation be used in the supply line to the flash system to ensure

consistent flash performance.

The effect of battery-voltage variations on electronic-flash energy

output was measured by monitoring the voltage drop across the battery

supply and the radiant-energy output of the flash system during a series of 15 consecutive shots. The voltage decreased from ^19 V to

397 V during the series. The resultant energy output as measured with

the energy meter decreased linearly by approximately 11%, as shown in

table 1. The percentage change in radiant energy Is again on the order

of double the percentage change in voltage. The Interval between

flashes was two minutes or longer to allow the flash unit to recharge.

Nevertheless, the battery voltage dropped gradually during the test,

Indicating that the flash-system performance would be more consistent

if the system were operated from a regulated a-c line. It should be

noted that the batteries used in these tests had been used for several

hundred shots previously. New batteries would probably produce more

repeatable flash energies.

2.2 Effect of Various-Sized Apertures on Energy-Meter Readings

Geometrical relationships between the energy-meter sensor, the

source, and the paths followed by radiant energy from source to sensor

vary considerably for the various source-sensor distances and sources

used in the method. Extensions of the method have been proposed using

narrow-angle, high-energy sources. For these reasons, the response of

the energy meter was investigated with various-sized apertures placed

at the front end of the sensor collimating tube. Apertures with diameters of 0.38, 0.53, 0.75, 1.06, 1.50, 2.12, and 3-00 cm were used.

These diameters were chosen so that each aperture has twice the area

of the next smaller aperture. Three tests with each aperture were run

with a No. 5 flashbulb as source 7 cm from the energy-meter sensor.

The results as shown In table 2 indicate that the energy approximately

doubles with doubling of the area until a diameter approximately equal

to that of the energy-meter sensor (1.15 cm)" is reached. For the

apertures with diameters of 1.50, 2.12, and 3-00 cm, the energy increases by less than a factor of two with each doubling of aperture

area, with the relative Increase becoming progressively smaller as the

aperture size becomes larger.

"The sensor diameter is also comparable to the diameter of the diaphragm

of the largest transducer tested.
2.3 Effect of Angle of Incidence on Transducer Response

The response of transducer Z to thermal radiant-energy transients

impinging on the diaphragm in directions 30, 60, and 90° from the

normal to the diaphragm was investigated.

It was necessary to remove the transducer mounting plug from the

fixture housing to perform these tests, as the housing would otherwise

shield the transducer from radiation entering the fixture at more than

a few degrees from the normal. A simple mounting pedestal was fabricated

on which the plug and transducer could be rotated about a vertical axis

through the center of the transducer diaphragm surface.

The tests were conducted with the center of the transducer diaphragm

7 cm from the center plane of the No. 5 flashbulb source. Five runs were

made at normal incidence and three runs each at 30, 60, and 90° from the

normal. The results are given in table 2.

At 30° from the normal, the zero shift of test transducer Z was

83% of the zero shift at normal incidence. At 60° from the normal, the

zero shift was of that at normal incidence, and at 90°, it was k%.

These figures correspond closely with the projected area of the transducer diaphragm as seen by the beam of radiation at each angle. The

areas would be S7% of the normal area at 30°, 501 at 60°, and 0 at 90°.

Comparison of the data of table 3 with data given in tables k or

5 shows that the zero shift of transducer Z resulting from ignition of

a No. 5 flashbulb at a source-transducer distance of 7 cm is approximately 20% smaller when the transducer is mounted on the pedestal

described above than when it is mounted in the fixture used in the

method. A probable explanation is that internal reflections in the

mounting fixture increase the total amount of energy incident on

the diaphragm.

2.k Effect of Reflectors on Transducer Response

A brief investigation to determine the gain in energy level that

could be achieved with the use of reflectors behind the energy source

showed that by using reflectors designed for photographic purposes, an

increase of about ]8% was achieved with the No. 5 and No. 22 flashbulbs,

and about 3^0% with the electronic flash at 150 J, at a transducersource distance of 7 cm, as shown by the data in table 3.

Energy levels impinging upon transducer Z with and without the

reflectors behind the sources were compared by measuring the resultant

zero shift of the transducer. In the tests with No. 5 and No. 22

flashbulbs mounted vertically as sources, a reflector from a photoflash

gun was positioned behind the bulbs. This reflector has a mirror finish,

a diameter of 14.2 cm, and a depth of 3-4 cm. With the reflector in

place, the distance from the center of the bulb to the reflector surface

is approximately 3-7 cm.
-5-

The reflector supplied with the electronic flash unit was used

with the electronic flash. This reflector has a satin finish, a diameter of 13.5 cm, and a depth of 6.8 cm. In use, the flashtube base

passes through the center of the reflector, and the center of the tube

is approximately 2.6 cm from the reflector surface.

The use of a reflector, while increasing the level of energy

available, renders energy monitoring difficult, since an energy sensor

detector cannot be located in the normal position on the optical bench.

Therefore, the use of a reflector as part of the method is not recommended unless the greater amount of energy available for a given test

is an overriding consideration.

2.5 Effect on Method of Energy Lost in Glass Window

The transducer mounting fixture was designed to permit the transducer to be subjected to pressures above or below atmospheric pressure

during exposure to thermal radiant energy entering the fixture through

a glass window. The significance of the effect of this glass window on

transducer response was investigated by measuring the zero shift of

transducer Z with and without the window in place. No. 5 flashbulbs,

7 cm from the transducer, were used in these tests. Table 5 shows that

for the ten shots without the window, the average transducer zero shift

was 93.7 mV, and the average energy-meter reading 586.4 mJ * cm~^

,

corresponding to a radiation sensitivity of 0.160 V • cm^ • J"^. With

the window in place in the transducer fixture, the average zero shift

was 89.8 mV and the average energy-meter reading 568.3 mJ • cm"^

,

corresponding to a radiation sensitivity of O.I58 V • cm^ • J~^.

Adjusting the data for the differences in energy levels shows that the

zero shift with the window is only 1.11 less than that without for

transducer Z. Unless a given transducer diaphragm material were especially sensitive to the effects of radiation of wavelengths absorbed

by the window, this result may be taken to indicate that the presence

of the window will, in general, have no significant effect on the results of the method.

2.6 Effect on Method of Increased Air Pressure from Heating

The possibility existed that the air in the closed volume of the

mounting fixture would itself be heated by energy from the source to

a significant degree. This heating would result in an instantaneous

change in air pressure which in turn would be sensed by the test

transducer. To investigate the significance of this effect, three

tests were run with transducers M and Z with the fixture at a vacuum

pressure of 3.4 Pa absolute (25 ym Hg absolute). The results were

compared with results from tests under the same conditions of distance

and source, but with the fixture at atmospheric ambient pressure. The

data are given in table 6. No significant difference between the results of the two sets of tests is seen. The conclusion may be drawn

that any "pressurizing" effect resulting from the heating of air in

the mounting fixture can be ignored for the purpose of the method.
2.7 Effect on Transducer of Exposure to Full-Scale Pressure

A series of 9 tests was run to investigate how transducer response

to a thermal transient was affected when the transducer was exposed to

pressure above ambient atmospheric in the mounting fixture. The pressure

chosen was the full-scale pressure for the two transducers used (M and Z)

,

3k5 kPa.

Transducer Z is a semiconductor strain-gage type and was chosen for

this investigation because its zero shift at atmospheric ambient was well

characterized and positive in direction. Transducer M is a semiconductor

strain-gage type with a metal diaphragm and was also known to have a positive zero shift. Three tests were made with each transducer at atmospheric ambient and at 3^5 kPa, with the tests at 3^5 kPa first. Tests

were run with the transducer diaphragm 7 cm from the center plane of the

No. 5 flashbulb source. The data are given in table 6.

As might be expected, the results show that the shift in the response measured when the transducer is exposed to full-scale pressure

is larger than the zero shift. The differences, however, are small.

For transducer M, the shift at 3^5 kPa is approximately 38% of the fullscale output (38% FS) , and the zero shift measured immediately following

the test at full-scale pressure is approximately 3^% FS. The corresponding figures for transducer Z are ]3% FS and ]G% FS, respectively. These

results suggest that for the intended screening purposes, ambient atmospheric pressure may be specified for the method with no significant loss

in screening capability compared to tests run at pressures higher than

ambient. Special circumstances, such as application of the method to

transducers known to have a strongly enhanced, non-linear pressure response over some part of their rated range, may require ad hoc treatment .

2.8 Evaluation of Flood-Flash FF-33 Lamps

Measurements of (l) the variation in intensity with distance from

flood-flash FF-33 lamps as source and (2) the repeatability of the method

with this source were delayed until this reporting period because the

FF-33 lamps were not previously available. These long-duration flashlamps (2.3 s compared to approximately 0.03 s for No. 5 and No. 22 flashbulbs) were designed for use in automobile crash photography and, according to the manufacturer, the amplitude-time waveform of the radiation

output is roughly triangular in shape. However, oscilloscope traces of

photodiode output for these lamps were found to be characterized by a number of high-amplitude spikes, as well as longer duration fluctuations

of considerable amplitude (on the order of the 25% of the maximum).

These phenomena are presumed to result from erratic burning of the FF-33

lamps and were seen in all photodiode traces for these lamps.

Investigation of available energy as a function of FF-33 sourcetransducer distance was carried out in a similar fashion to that described in previous reports for the short-duration sources, with the

following exceptions: (1) A power meter, calibrated in watts, was
-7-

substituted for the energy meter, because the energy meter is not

capable of reading energy pulses with a duration greater than 50 ms.

The maximum output of the power meter was read visually on a panel

meter "on the fly." That is, the operator was required to estimate

the maximum upward excursion of the (relatively slowly moving) meter

pointer. Output from the power meter was also displayed on an oscilloscope. (2) Tests were run in 1-cm increments from 8 cm to 15 cm; the

size of the FF-33 bulbs prevented tests at source-sensor distances less

than 8 cm, and the low energy level (as determined by transducer response) suggested 15 cm as a good termination point as was the case for

measurements with the electronic flash at 150 J. The data are given in

table 7.

Repeatability tests with the flood-flash FF-33 bulbs as the method

source were carried out at a source-sensor and source- transducer distance

of 12 cm and consisted of 10 consecutive shots. Transducer Z was the

test transducer. The effects of the long duration (about 2 s) of the

FF-33 flash, of the use of a power meter instead of an energy meter, and

especially of the observed erratic burning complicate the reporting of

results. Peal<-power levels as determined from the analog output of the

power meter, displayed and photographed on an oscilloscope, show variations of up to ]2% below and ]8% above the ten-shot average; the data

are given in table 8. Peak-power levels determined by reading the maximum excursion of the panel meter show variations of similar magnitude.

Peak transducer zero shifts, as determined from a photographed oscilloscope display, show variations of up to 2k% below and up to 21^ above the

ten-shot average. Comparison of transducer Z zero shift with the powermeter output from one shot to another shows little or no correlation between the two quantities. An explanation may be that the energy output

from the FF-33 bulbs varies greatly in azimuth, as is suggested by the

erratic burning. As was the case to a much lesser extent with the shortduration sources, the transducer under test and the sensing meter would

"see" different power levels for the same test run. As described earlier,

the photodiode response to FF-33 bulbs was characterized by the presence

of spikes and other fluctuations, and average levels could not be determined with any reasonable precision. Photodiode measurements were therefore not useful in repeatability tests with FF-33 bulbs.

Following these tests no further work was carried out with FF-33

bulbs as the method source. This type is not recommended for this

application because it exhibits erratic burning and apparent large

variations in output from one bulb to another, and because it has lower

output and larger size relative to other sources available.

3. RESULTS OF TESTING TRANSDUCERS USING THE METHOD

The work carried out to date has been primarily concerned with

the development of the method. In the course of this work, the zero

shift of transducer Z as determined by the method has been well characterized. It is of interest to investigate by the method the zero shifts

of other models of the same type as transducer Z and of other transducer

types and to compare these results.
Accordingly, 25 transducers, including Z as a control, were selected

and tested by the method with a distance of 7 cm" between the transducer

diaphragm and the center plane of the No. 22 flashbulb source. All measurements were made with the transducer exposed to ambient atmospheric

pressure. Each transducer was tested three times, and an average zero

shift computed. These average zero shifts were expressed as a percentage

of the transducer full-scale output and are given in table 9, along with

a brief indication of transducer type, range, pressure equivalent to

the zero shift, and percent full-scale radiation sensitivity. The average zero shifts ranged from about 0.k% of full-scale output for transducer

S to k3Q% of full-scale output for transducer N. The semiconductor straingage transducers as a class exhibited the greatest vulnerability of any

transducer type to the thermal radiant-energy transients produced in the

method.

PRELIMINARY WORK FOR NEW TASK

Planning was initiated for a new task with experimental work scheduled

to begin in FY 1976. The task is to evaluate the effectiveness of schemes

in use or proposed to reduce the effects produced by thermal radiant-energy

transients and other thermal inputs on pressure transducer response. The

intent is to use the test method discussed in the other sections of this

report for evaluating protection from thermal radiant-energy transients

and to modify this method as required for generating other thermal inputs

to the test transducer and protection scheme. The task assignment lists

these considerations: "(a) protection from radiated and/or convected

transients of various amplitudes and durations; (b) effects of any protection scheme on transducer performance such as increased acceleration

sensitivity, degradation in dynamic performance, etc.; (c) ability of the

protection scheme to survive the adverse environments associated with the

real physical processes generating these transients." Goals of the work

include development, for users, of guidelines and protective schemes for

the use of existing pressure transducers in applications in which thermal

inputs are present and, for manufacturers, recommendations relating to

pressure transducer design and construction.

As a starting point, information concerning types of pressure

transducers used, pressure ranges, nature of thermal inputs, nature of

applications, protection schemes, nature of any initial screening tests,

and the like was sought from a sampling of transducer users at test

ranges and other agencies. The responses indicated such a wide variety

of applications, transducers, and measurement conditions that it was not

possible to select representative pressure ranges and test conditions.

With the concurrence of NAVAIR and the Transducer Committee, it was proposed that work would begin (l) using the test method with No. 22 flashbulbs as source, (2) with flush-diaphragm transducers having full-scale

ranges of 0.35 and 6.9 MPa and either strain-gage or piezoelectric sensing

"This distance is convenient for the No. 22 flashbulb. The energy levels

available at the transducer diaphragm are considerable (approximately

1.7 J • cm"^) and there is good access to flashbulb and mounting fixture.
elements, and (3) with thermal protection either provided by diaphragm

coatings applied in-house or based on path geometry. Based on the results

of these investigations, further work covering a broader range of conditions may be proposed.

5. OTHER AGENCY WORK

Two tasks are nearly completed for other Government agencies

outside the NBS InterAgency Transducer Project. Since the objectives

of those tasks fall within the area of the NBS InterAgency Project,

brief reports on these tasks are presented:

5.1 Development of a Dynamic Pressure Cal i bration Method

(For NASA Langley Research Center)

A draft of the final report has been written, with authors, title,

and abstract as follows:

Vezzetti, C. F., Hilten, J. S., Mayo-Wells, J. F. , and Lederer,

P. S. , A New Dynamic Pressure Source for the Calibration of Pressure

Transducers (to be published as NBS Tech Note)

A dynamic pressure source is described for producing

sinusoidal ly varying pressures of up to 3^ kPa zero-to-peak,

over the frequency range of approximately 50 Hz to 2 kHz.

The source is intended for the dynamic calibration of pressure transducers and consists of a liquid-filled cylindrical

vessel, 11-cm in height, mounted upright on the armature of

a vibration exciter which is driven by an amplified sinusoidal ly varying voltage. The transducer to be calibrated is

mounted near the base of the thick-walled aluminum tube

forming the vessel so that the pressure-sensitive element

is in contact with the liquid in the tube. A section of

the tube is filled with small steel balls to damp the motion of the 10-St dimethyl siloxane working fluid in order

to extend the useful frequency range to higher frequencies

than would be provided by an undamped system.

The dynamic response of six transducers provided by the

sponsor was evaluated using the pressure source; the results

of these calibrations are given.

5.2 Pogo Pressure-Measuring System for Space Shuttle

(for NASA Marshall Space Flight Center)

The windmill calibrator was assembled in late December

197^. When tested, the device did not operate properly because of excessive friction in the air bearings. This condition was traced to improper machining of the bearing journals and faulty installation of the bearings. Furthermore,

the bearing manufacturer's specification of the proper shaft

diameter was found to be incorrect. The journal assembly

and shaft were therefore remachined. These operations were

completed in early March 1975, and the calibrator was reassembled. As soon as the air supply was turned on, the
-10-

rotating structure vibrated severely. After examination,

the air bearings themselves were found to be poorly machined,

and questions were raised about the basic design. As a result,

the calibrator was redesigned to accept previously used air

bearings of smaller diameter. The redesign also required a new shaft. This new version of the calibrator was put into

operation in early June 1975 and appeared to function well.

A number of pogo pressure transducers were successfully

calibrated using the windmill apparatus and the liquid-filled

tube on the vibration exciter.

Two organizations within Rockwell Corporation, the

prime contractor for the space shuttle, have indicated that

they plan to copy the windmill calibrator and to use it in

the dynamic calibration of pressure transducers for pogo

and similar applications.

6. TRANSDUCER-RELATED NBS PUBLICATIONS

Abstracts are presented below of work completed in other parts

of the National Bureau of Standards which is applicable to transducers

6.1 Pontius, P. E., Notes on the Fundamentals of Measurement

and Measurements as a Production Process, September 197^ > NBSIR 7^-5?5

The concept of a measurement process as a production

process is relatively new, having evolved in the last ten

years. There have been significant contributions from many

sources which have served to refine the initial ideas. The

generalized concept of a measurement process is discussed

together with techniques and examples for verifying the

validity of the result. While some of the techniques may

not be appropriate for certain highly specialized measurement processes, it is felt that the concepts are applicable

to practically all measurement processes. For certain types

of general measurement processes, which must operate in a variety of environments, and which must accommodate a variety

of materials and properties, the techniques have been invaluable in understanding the manner in which measurement processes operate in a "real" world.

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

in Calibration, September 197^, NBSIR 7^-587

This paper presents a discussion of the techniques of

statistics that arise in the analysis of data from the

comparative experiments used in the calibration of objects

relative to a reference group of standards. In calibration

one usually measures differences between nominally equal

objects and uses the values assigned to the standards as the

linear restraint to bring the system up to full rank. The

use of the method of least squares in this situation is

discussed with examples taken from the calibration work

of the National Bureau of Standards.
-11-

This summary of statistical techniques is intended for

metrologists and was presented at the NBS seminar on HighEfficiency Methods for Dimensional Calibrations given 10-11

June 197^.

6.3 Schoonover, R. M. , and Ku, H. H. , Calibration of Platinum

Resistance Thermometers Using an I ntercompar i son Scheme , December 197^, NBSIR 7^-586

In this report we describe a procedure for the calibration

of capsule type platinum resistance thermometers, PRT(s), using

one or more standard platinum resistance thermometers, SPRT(s),

in the temperature range of 0-35°C. These PRT(s) were designed

to be used in density work through hydrostatic weighing where

SPRT(s) cannot be used because of space and other limitations,

but the procedure is thought to be generally useful in other

applications as well.

The schedule of i ntercompa r i sons was designed to eliminate

possible trends in temperature variations of the constant temperature bath setup. Results of calibration can be expressed either

in terms of the two constants alpha (a) and delta (6), or in a table relating R(t)/R(0) to tgg within the range of calibrations.

The uncertainty of the values of tgg calibrated by this

procedure is believed to be within 2 millidegrees Celsius,

not including the uncertainty of the SPRT that is used as

standard.

7. REFERENCES

[1] Lederer, P. S, , and Hilten, J. S. , NBS InterAgency Transducer

Project - Progress Report Covering Period July 1, 197^ to

September 30, 197^, NBSIR 75-65^ (February 1975).

[2] Lederer, P. A., Hilten, J. S., and Vezzetti, C. F. , NBS InterAgency Transducer Project - Progress Report Covering Period

October 1, 197^ to December 31, 197^, NBSIR 75-732 (June 1975).

USCOMM-NBS-DC

TABLE 1

EFFECT OF SUPPLY-VOLTAGE VARIATION ON PERFORMANCE

OF THE ELECTRONIC FLASH*

Tests with Line Power Supply Tests with "attery Power Supply

Supply

Voltage

(a-c V)

110

112

114

116

118

Run

12

3

av

12

3

av

Energy Meter

Reading

(mJ'cm"^)

81.9

80.4

83.9

82.1

91.1

84.7

92.9

89.6

12

3

av

2

3

av

12

3

av

92.6

90.0

95.3

92.6

98.8

92.7

96.5

96.0

97.0

94.2

102.4

97.9

Supply

Voltage

(d-c V)

Energy Metf.r

Keadinq

(mJ*cm'^)

419 73.7

414 71.9

411 70.7

409 70.0

408 69.4

406 68.5

67.6

'MJo 0/ .C.

402 66.8

401 66.3

400 66.2

399 65.9

398 65.6

398 65.4

397 64.7

120

2

3

100.5

104.8

103.5

av 102.9

*The electronic flash was operated at a setting of 150 J; the energy meter was

7.5 cm from the center of the flashtube.
TABLE 2

ENERGY-METER READINGS AS A FUNCTION OF CIRCULAR APERTURE SIZE

Averaged

Aperture Diameter Aperture Area Energy-Meter Reading

cm cm^ mJ'Cm

0.38 0.113 46.9

0.53 0.221 104

0.75 0.442 180

1.06 0.882 306

1.50 1.77 486

2.12 3.53 536

3.00 7.07 697

*A11 measurements were taken with the energy-meter sensor 7 cm from

the center plane of the No. 5 flashbulb source.
TABLE 3

TRANSDUCER Z ZERO SHIFT IN RESPONSE TO

THERMAL RADIANT-ENERGY TRANSIENTS

INCIDENT AT SELECTED ANGLES

Angle of

Incidence

(rad) [deg] Run

Zero

Shift*

(mV)

0 1 72

0 2 81

0 3 69

0 4 69

0 5 74

av 73.0

Ratio of

Zero Shift at Test Angle tc

Zero Shift at Normal Incidence

1.00

1 .00

1.00

1 .00

1 .00

1.00

F [30] 1 59 0.81

F [30] 2 68 0.93

^ [30] 3 67 0.92

av 64.7 0.89

T [60] 1 40 0.55

T [60] 2 37 0.51

T [60] 3 _46 0.63

av 41.0 0.56

TT

[90] 1 2.5 0.03

T [90] 2 2.5 0.03

^ [90] 3 4.5 0.06

av 3.2 0.04

*A11 measurements were taken with constant electrical excitation supplied to

transducer and at ambient atmospheric pressure.
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GLASS WINDOW ENERGY TRANSMISSION LOSS

AS SEEN IN TRANSDUCER Z ZERO SHIFT

- , Transducer Zero Shift* Energy Meter Reading

(mV) (mJ*cm"2)

Run with window without window

1 78 665

2 95 660

3 94 579

4 104 561

5 94 551

6 94 592

7 91 519

8 96 569

9

' 91 581

10 100 587

av 93.7 av 586.4

sample SD 6.8 sample SD 45.3

84 600

90 576

95 557

97 560

98 549

90 589

80 580

82 524

88 582

94 -A - 566

av 89.8 av 568.3

sample SD 6.3 sample SD 22.0

*A11 measurements were taken with constant electrical excitation supplied to the

transducer and at ambient atmospheric pressure; the transducer diaphragm was 7 cm

from the center plane of the No. 5 flashbulb source.
TABLE 6

SHIFT IN TRANSDUCER OUTPUT FROM INCIDENT THERMAL RADIANT-ENERGY TRANSIENTS

WITH TRANSDUCER MEASURING ELEVATED, AMBIENT, AND VACUUM PRESSURE,

FOR SELECTED TRANSDUCERS

Test Fixture

Pressure Transducer

Z

Output Shift* (mV)

Transducer

M

345 kPa

[50 psi]

av

97

95

96

96 av

28

30

28

29

Ambient

Atmospheric

av

82

78

80

80 av

25

26

25

25

Vacuum

(3.4 Pa absolute)

[25 urn Hg absolute]

78

92

85

22

26

25

av 85 av 24

*A11 measurements were taken with the transducer diaphragm 7 cm from the

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TABLE 7

TRANSDUCER Z ZERO SHIFT IN RESPONSE TO THERMAL RADIANT-ENERGY

TRANSIENTS FROM FF-33 FLASHBULB SOURCE

AS A FUNCTION OF SOURCE-TRANSDUCER DISTANCE

Distance from Energy Transducer Z Power-Meter

Source to Transducer Zero Shift Reading

Diaphragm (% of full scale)

(cm) (W)** Corrected*

to 1 cm^

(W)

8 23.2 30.3 10.7

9 20.0 27.9 9.8

10 15.2 18.6 6.5

11 14.4 18.3 6.4

12 9.7 12.2 4.3

13 8.5 8.4 3.0

14 8.2 8.0 2.8

15 6.9 6.8 2.4

* All measurements were taken with constant electrical excitation supplied to

the transducer and at ambient atmospheric pressure.

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are also shown for 1 cm^, the area of the energy-meter sensor.
TABLE 8

TRANSDUCER Z ZERO SHIFT IN RESPONSE TO

THERMAL RADIANT-ENERGY TRANSIENTS FROM FF-33 FLASHBULB SOURCE

Run

12

3

4

5

6

7

8

9

10

Transducer Zero Shift

as Percentage of

10-Run Average*

96.6

96.6

92.5

103.8

107.9

103.8

102.8

76.1

121.3

98.7

Power Meter Output

as Percentage of

10-Run Average

87.9

101.1

102.7

93.7

105.2

95.3

93.7

98.6

103.5

118.3

*A11 measurements were taken with constant electrical excitation supplied to the

transducer and at ambient atmospheric pressure.

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NBS-114A (REV. 7-73)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR RHPORT NO.

NBSIR 76-1038

2. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

NBS InterAgency Transducer Project

Progress Report No. 3

5. Publication Date

April 1976

6. Performing Organization Code j

7. AUTHOR(S)

Paul S. Lederer and John S. Hilten

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Naval Air Systems Command Transducer Committee TG/RCC

Washington, DC 20361 c/o Div. 9486

Sandia Laboratories

Albuquerque, NM 87115

13. Type of Report & Period

Covered | nter im

1/1/75 to 6/30/75

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less (actual summary almost sigpificant information. If document includes a significant

bibliography or literature survey, mention it here.)

Concluding efforts related to the development of a test method for evaluating the

effects of short-duration, thermal radiant-energy transients on pressure-transducer

response are described. The method consists of monitoring pressure-transducer

output (zero shift with the transducer at atmospheric pressure) as the transducer

is exposed to radiation resulting from the ignition of a photographic flashbulb or

from the discharge of an electronic flash. Thermal energy pulses as great as 0.1

J/cm , with durations of about 6 ms , have been generated using an electronic flash;

pulses of up to 2.2 J/cm^, with durations of about 37 ms , have been generated using

No. 22 flashbulbs. Flood-flash FF-33 lamps were also investigated; their

use is not recommended. In tests with No. 22 bulbs, 25 commercial pressure

transducers have shown zero shifts ranging from 0.4^ to about 400^ of the

ful l-sca1e output.

Transducer-related tasks being performed for other agencies are also described

briefly, and other recent NBS publications of interest to the transducer

community are identified.

I ;

i

f

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons) - . , . , . , , Calibration; dynamic; electronic flash; photoflash bulb;

pressure; pressure measurement; pressure transducer; pressure transducer response;

response; thermal transient; transducer; zero shift.

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