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CO Q NBS TECHNICAL NOTE 1110

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U.S. DEPARTMENT OF COMMERCE /National Bureau of Standards
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards' was established by an act of Congress on March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology

and facilitate their effective application for public benefit. To this end, the Bureau conducts

research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau's technical work is per- formed by the National Measurement Laboratory, the National Engineering Laboratory, and

the Institute for Computer Sciences and Technology.

THE NATIONAL MEASUREMENT LABORATORY provides the national system of

physical and chemical and materials measurement: coordinates the system with measurement

systems of other nations and furnishes essential services leading to accurate and uniform

physical and chemical measurement throughout the Nation's scientific community, industry,

and commerce; conducts materials research leading to improved methods of measurement,

standards, and data on the properties of materials needed by industry, commerce, educational

institutions, and Government: provides advisory and research services to other Government

agencies: develops, produces, and distributes Standard Reference Materials; and provides

calibration services. The Laboratory consists of the following centers:

Absolute Physical Quantities2 — Radiation Research — Thermodynamics and

Molecular Science — Analytical Chemistry — Materials Science. THE NATIONAL ENGINEERING LABORATORY provides technology and technical ser- vices to the public and private sectors to address national needs and to solve national problems: conducts research in engineering and applied science in support of these efforts; builds and maintains competence in the necessary disciplines required to carry out this research and technical service; develops engineering data and measurement capabilities;

provides engineering measurement traceability services; develops test methods and proposes

engineering standards and code changes; develops and proposes new engineering practices;

and develops and improves mechanisms to transfer results of its research to the ultimate user. The Laboratory consists of the following centers:

Applied Mathematics — Electronics and Electrical Engineering2 — Mechanical

Engineering and Process Technology2 — Building Technology — Fire Research —

Consumer Product Technology — Field Methods.

THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts

research and provides scientific and technical services to aid Federal agencies in the selection, acquisition, application, and use of computer technology to improve effectiveness and

economy in Government operations in accordance with Public Law 89-306 (40 U.S.C. 759), relevant Executive Orders, and other directives: carries out this mission by managing the Federal Information Processing Standards Program, developing Federal ADP standards

guidelines, and managing Federal participation in ADP voluntary standardization activities: provides scientific and technological advisory services and assistance to Federal agencies; and

provides the technical foundation for computer-related policies of the Federal Government.

The Institute consists of the following centers:

Programming Science and Technology — Computer Systems Engineering.

: Headquarters and Laboratories at Gaithersburg. MD, unless otherwise noted: mailing address Washington. DC 20234.

: Some divisions within the center are located at Boulder, CO 80303.
NBS Interagency Transducer Project

1951-1979 - An Overview

Paul S. Lederer

National Engineering Laboratory

National Bureau of Standards

Washington, DC 20234

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U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Luther H. Hodges, Jr., Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Issued August 1979
National Bureau of Standards Technical Note 1110

Nat. Bur. Stand. (U.S.), Tech. Note 1110, 45 pages (Aug. 1979) CODEN: NBTNAE

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1979

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

Stock No. 003-003- Price $ (Add 25 percent additional for other than U.S. mailing)
CONTENTS

Introduction 1

Background 1

History 2

Objectives 3

Work Areas 4

Needs and Feedback 4

Relations with Transducer Committee, Telemetry Working

Group, IRIG 5

Participation in Voluntary Standardization Activities 6

Information Dissemination 6

Accomplishments 7

1. Earth's Field Static Calibrator for Accel erometers 7 2. Earth's Field Dynamic Calibrator for Accel erometers 7

3. Dual Centrifuge 8

4. Torsional Vibration Calibrator 8

5. Shock Tube 9

6. Pneumatic Step Function Calibrator 9

7. Liquid Medium Step Function Calibrator 10

8. Transient Recorder and Frequency Analysis Scheme. . . . ... . 10

9. Thermal Gradient Testing Method 11 10. "Life Cycling" Technique for Pressure Transducers 11

11. Computation of Useful Frequency Range of

Piezoelectric Accel erometers 12

12. Effects of High-Temperature Storage on Strain Gage

Pressure Transducers 12

13. Hydraulic Sinusoidal Pressure Calibrator 13

14. Thermal Transient Tests Using Laser 13

15. Thermal Transient Test for Piezoelectric Accel erometers .... 13

16. Vibratory Phenomena in Liquid-Filled Cylinder 13

17. Flashbulb Thermal Transient Test Method 14

18. Dynamic Pressure Calibration Source 14

19. Dynamic Pressure Calibrations at High Static Pressures 14

20. Thermal Transient Protection for Pressure Transducers 15

Applications of Project Results 15

Publications 17

Acknowledgment 20

figures 21

i i i

NBS Interagency Transducer Project

1951-1979 -- An Overview

Paul S. Lederer

Abstract

Between 1951 and 1979, the National Bureau of Standards was engaged in c continuing project to study the performance of sensory transducers,

primarily those used in telemetry. This project has been supported

by agencies of the Defense Department and NASA. This report provides

a brief description of the background and history of the project, of

its objectives, of some of the techniques and specialized facilities

developed and used, and of some of the publications that have been

issued from the project.

Key Words: Transducer, telemetry, Interagency Transducer Project,

dynamic calibration, evaluation, performance characteristics.

Introduction

As a result of the 1978-79 reorganization of the National Bureau of

Standards, the NBS Interagency Transducer Project was terminated. In

view of the substantial impact which this project has had on the

transducer community, it seems proper to summarize its background

and history, briefly describe its accomplishments, and list its

publ ications.

Background

In missile, rocket, and aircraft flight test instrumentation, the

weakest link in the telemetering system is often the sensory

transducer, either because of its limiting performance or because

of limited knowledge concerning its performance. This situation

results in part from the fact that in the design of transducers,

adequate information has not been available to manufacturers as to the

performance needed by users, and in part from the fact that adequate

information on the performance of transducers has not been available to

guide the selection of transducers by missile, rocket, and aircraft

instrumentation designers. To supplement the often meager information

supplied by manufacturers, as well as to check the manufacturer's

claims on performance, users frequently have been forced to devise

and carry out laboratory tests of their own. Techniques and equipment

for such tests, particularly for determining performance under dynamic

conditions, have often not been available. Such methods as have been

available have not been standardized adequately and have often produced

different results when used in different laboratories.

1
History

Recognition of these problems led in 1951 to the establishment of a "Transducer Project" at the National Bureau of Standards under the

sponsorship of the Bureau of Aeronautics, U.S. Navy. The objectives

were threefold: to obtain additional performance data on sensing

instruments for use with telemetering systems in guided missiles,

to establish a standard report form for evaluation tests, and to

evaluate and recommend standard testing procedures for these

instruments.

This work was undertaken by NBS because the development of new and

improved measurement techniques, both as applied to the measurement

of transducer performance and to the development of improved

transducers, falls within NBS' central continuing mission of providing

national leadership in tie development and use of accurate and

uniform techniques of physical measurement. At the same time, the

ongoing program of NBS on measurement, calibration, and instrument

development, particularly of such quantities as force, strain,

temperature, mass, acceleration, pressure, etc., provides knowledge,

experience, and facilities complementary to the telemetering transducer

project. This expertise has contributed directly to the development

of some of the techniques used and developed by this project.

The first performance test report resulting from this project was issued in March 1952. Beginning in 1953, the Ballistic Research

Laboratories, Aberdeen Proving Ground, U.S. Army joined the Bureau

of Aeronautics in providing project support. In 1955, White Sands

Proving Ground took over from the Ballistic Research Laboratories

its share of project support. It became a Tri-Service project

in 1956, when the Wright Air Development Center, U.S. Air Force

added its support. This arrangement continued until 1963, when

the National Aeronautics and Space Administration joined as a sponsor.

Shortly after that, however, the Army (White Sands Proving Ground)

discontinued its support. NASA supported the work for four years, and

Air Force funding continued until 1968. Navy funding was continuous

from 1952 through 1976 (except for 1973 and 1974). Member ranges

of the Range Commanders Council also put up shares of support for

the work between 1974 and 1978, as did the National Bureau of

Standards from 1974 to 1979. It should be noted that all of the

funding referred to so far was for "generic" work, i.e., broad based,

fundamental studies leading to better understanding of transducer

performance and the development of transducer calibration and

evaluation methods.

To make up funding deficiencies without losing project staff with

valuable expertise, specific tasks were accepted from other government

agencies starting in 1968. In all cases, these were mission-oriented

tasks relating to transducer calibration and evaluation and thus

fitting within the major objectives of the project. The major
reorganization of the National Bureau of Standards in 1978 and

resulting reprogramming of certain activities led to the decision

to terminate the NBS Interagency Transducer Project at the end of

Fiscal Year 1979.

The project itself, which was started in the Office of Basic

Instrumentation of the National Bureau of Standards, was transferred

to the Mechanical Instruments Section in 1954, and to the

Engineering Electronics Section in 1964. In 1965, the project came

home again to the Basic Instrumentation Section. The Section became

the Instrumentation Applications Section in 1970, Components and

Applications Section in 1973 and, finally, Sensory Transducer

Section in 1977.

The staff of the project varied from two to eight professionals

during its existence, averaging four during most of its existence.

About 115 publications originated from the work of the project

(not counting voluntary standards which staff members helped write),

with a total professional effort of roughly 120 man years.

Funding received during the project duration was approximately the

following (records are not complete) in order of size: U.S. Navy

$ 1093 k, Mission-Related Tasks $ 719 k, U.S. Air Force $ 656 k,

NBS $ 535 k, U.S. Army $ 371 k, NASA $ 120 k, for a grand total

of $ 3494 k or about $ 3.5 million during the 28-year duration of

the project.

Objectives

The original objectives of the project as stated in the history were somewhat modified circa 1959, thus: to obtain performance data on selected telemetering transducers, and to develop and evaluate testing

procedures for transducers. The modifications resulted from the

realization that resources of staff and facilities were, and would

remain inadequate, for performance testing of all types of transducers,

and that optimum benefits would accrue to sponsors from tests only

on certain transducers to be selected on the basis of potentially

superior performance or potential weakness; verification of either

characteristic being of great practical importance to users. Recognition of inadequacy or non-existence of testing procedures

in some areas led to efforts to develop adequate procedures.

Since 1959 there have been some further slight modifications and

the final objectives of the Interagency Transducer Project may be

stated as:

"Investigation of the performance characteristics of electromechanical telemetering transducers required for making

meaningful measurements of physical quantities."
"Development of techniques and apparatus for the determination

of these characteristics."

"Effective dissemination of the knowledge obtained."

Work Areas

To achieve these objectives, project work was conducted in six areas.

The first area encompassed the precise measurement of changing physical

quantities. This necessitated the development of techniques and

apparatus for evaluating the dynamic measurement capabilities of

transducers in areas where such techniques did not exist or were inadequate.

The second area was concerned with the effects on transducers of the

environments in which they are used or stored. The environment in which

a transducer operates while performing measurements may have a detrimental

effect on the quality of the measurements. Rapidly changing environments

may pose particularly severe problems. This required the development of

techniques and apparatus for simulating environments and evaluating their

effects on the measurement capabilities of transducers.

The third area dealt with "durability" of transducers and sensors in

service. This is of particular importance in industrial service, where

sensors are expected to perform properly over extended periods of time.

Equipment and procedures for "life testing" of transducers and sensors

were developed.

The fourth area dealt with the study and investigation of principles

and materials which may lead to improved evaluation techniques and

apparatus

.

The fifth area included participation in efforts of professional societies

and other organizations to develop standards and recommended practices

for transducers and sensors.

Finally, sixth, transducers, especially those with novel operating

principles or employing newly developed materials, may exhibit unexpected

shortcomings and, therefore, require thorough evaluation to establish

their performance characteristics reliably. Such evaluations also provide

a means for establishing the validity of existing evaluation procedures

and equipment, including those developed as part of the work in the areas listed above. This was also to help to identify areas in which additional

work is required.

Needs and Feedback

Selection of the tasks to be undertaken to fulfill the objectives of

the project was based on the needs of the sponsoring agencies and the

capabilities of the project staff. Needs were established by consultation

4
with representatives of the sponsors and their contractors. Information

as to needs in areas of measurement and calibration was also obtained

by participation in professional society meetings, visits to sponsoring

agencies and their laboratories, personal contacts with transducer

users, careful perusal of current scientific literature, and, in particular,

through the agency of the Transducer Committee of the IRIG Telemetry

Working Group.

Relations With Transducer Committee, Telemetry Working Group, IRIG

Information gathered on the needs of transducer users in areas within

the purview of the project had never been as comprehensive as desired.

Accordingly, at the eleventh meeting of the Inter-Range Telemetry Working

Group (April 1958), and at the request of the National Bureau of Standards

and the Bureau of Aeronautics, a Committee on Transducers was established

by the Telemetry Working Group. The purpose of this committee was to

provide more effective feedback and guidance to the NBS Transducer Project

by IRTWG, as well as to provide IRTWG with information of significant

developments in the field of telemetry transducers. Close liaison between

the NBS project and IRTWG was desirable to assure maximum usefulness to

the sponsors and to telemetry users generally.

In 1959, the Transducer Committee recommended that a symposium be held,

to be attended by representatives of member ranges, engineering societies

and other agencies having a direct interest in transducer developments.

The objectives of this symposium were to be: to publicize the goals of

the Transducer Committee; to determine the usefulness of standardization

of evaluation, calibration and specification procedures; to communicate

with related transducer programs directed by other non-(TWG)-Agencies;

and, to determine the extent of any coordinated efforts directed toward

improving transducer performance to keep pace with advanced telemetry

development.

The first Telemetry Transducer Symposium was held in February 1960

and it was the consensus of attendees that several areas of effort needed

immediate attention. These were (1) standard telemetry transducer

terminology, (2) recommended calibration procedures, and (3) establishment

of a clearinghouse for transducer calibration and evaluation reports.

Subsequent Transducer Workshops were held in July 1961, June 1962, and

June 1964. Participants have commented favorably on subjects covered

and on the value of the free exchange of information possible in the

informal atmosphere that prevailed at the meetings. A fifth Transducer

Workshop held in October 1967 at the new laboratories of the National

Bureau of Standards incorporated a panel session with audience participation

This format was kept during subsequent workshops which were held in

October 1969, April 1972, April 1975, and April 1977. A manufacturers

panel was added and formal proceedings were published after the workshops.

Attendance has averaged about 100 participants. A tenth Workshop is

planned for June 1979.
Participation in Voluntary Standardization Activities

In 1960, in response to transducer needs expressed by the aerospace

industry, the Instrument Society of America established a committee

to identify specific instrumentation areas requiring standardization.

The committee, the Survey Committee on Transducers for Aero-Space

Testing (SCOTFAST), conducted a survey among transducer users throughout the country and identified some specific needs in the

field of transducers. Among them were improved and uniform transducer

nomenclature and specification terminology, and standardization of

performance characteristic specifications, test methods, and

electrical requirements for certain classes of transducers used in

aerospace testing.

As a result of the survey, five subcommittees were established, each

to deal with one class of transducers, and a sixth subcommittee to

concern itself with nomenclature and specification terminology.

A tentative recommended practice "Nomenclature and Specification

Terminology for Aero-Space Test Transducers with Electrical Output"

(RP 37.1) was issued by ISA in April 1963.

One of the staff members of the NBS Transducer Project was asked

to join the SCOTFAST Committee shortly after its formation and was appointed chairman of the subcommittee dealing with strain gage

pressure transducers. Based on the experience gained with this class

of transducers in the NBS Interagency Transducer Project and with the

assistance of other subcommittee members, a tentative recommended

practice was written. This document, "Guide for Specifications and

Tests for Strain Gage Pressure Transducers for Aero-Space Testing,"

was released as ISA-RP 37.3 in April 1964.

Subsequently, additional standards documents dealing with transducers

were written by the various subcommittees and, ultimately, turned into

ANSI standards.

Project staff members participated in voluntary standards committees

of other organizations such as ASME, ANSI, ASTM, and SAE. At the end

of 1977, 42 voluntary transducer standards were identified, 16 of those

(38% of the total) had been written (wholly or partially) or critically

reviewed and/or revised by staff members of the NBS Interagency

Transducer Project.

Information Dissemination

A variety of means was used to attempt to meet the third project

objective: the effective dissemination of information.

Project publications were distributed to a mailing list of about 140

instrumentation people in government laboratories and industrial plants

throughout the country. In addition, all NBS Technical Notes were also

sold through the Government Printing Office, which by May 1978, had sold

a total of 8316 copies of 17 Technical Notes.
Project staff actively participated in the transducer workshops,

visited laboratories and plants, presented talks at technical society

meetings, and were consulted extensively through visits and telephone

calls.

As indicated earlier, project staff participated actively in voluntary

standardization efforts. A listing of committee affiliations follows:

Instrument Society of America

American National Standards

Institute

Standards and Practices Board

SP 37 "Measurement Transducers"

SP 37.3 "Strain Gage Pressure

Transducers"

SP 37.5 "Strain Gage Accel erometers 1

NIC 88 "Calibration of Instruments"

MC 88 Subcommittee on Pressure

American Society of Mechanical

Engineers

American Society of Testing

and Material

s

Society of Automotive

Engineers

"Pressure Technology"

El 0.07 "Reactor Instrumentation"

'Transducers" Subcommittee

Accompl ishments

During the course of the project, a number of techniques and devices

have been developed for the calibration and evaluation of transducers.

Brief descriptions follow:

1

.

Earth's Field Static Calibrator for Accel erometers [9]

This device as shown in Figure 1 consists of a precision machinist's

dividing head mounted on a surface plate and a precision level. A

carefully machined bracket attached to the dividing head serves as a mounting surface for the accelerometer. Calibration is accomplished

by rotating the bracket in the earth's gravitational field. From a precise

knowledge of the angle between the sensitive axis of the accelerometer

and the vertical, the value of the component of gravity acting on the

seismic mass can be computed. The system is simple, relatively

inexpensive and has an estimated limit of error of ±0.004 gn

.

2. Earth's Field Dynamic Calibrator For Accel erometers [19]

This device was developed to calibrate accel erometers at frequencies

from about 30 Hz down to about 0.5 Hz by rotating the transducer at

uniform velocity in the earth's gravitational field, the magnitude of which is

Figures in brackets refer to the publications listed in the Section

"Publications".
well known. The electrical connections to the accelerometer are made

through slip rings. An improved version of this device has been

completed with improved bearing supports and more constant rotational

speed and is shown in Figure 2. These changes were made to improve

accuracy of calibration. This and the previous device have the

limitation that the exciting force cannot exceed ±1 gn and the further

limitation that the accelerometer under test must have negligible

response to transverse excitation.

Three high-natural-frequency servo accelerometers were calibrated

from 2 Hz to 24 Hz. The agreement between the sinusoidal excitation

responses and the static response was within ±0.1% from 10 Hz to 20 Hz,

±0.2% from 22 Hz to 24 Hz, and ±0.5% from 2 Hz to 8 Hz (the deviations

from perfect agreement are attributed largely to accuracy limitations

of the voltmeter used).

The carefully confirmed discrepancies between experimentally determined

values of natural frequencies and damping ratios for linear and

rotational dynamic calibrations of low-natural -frequency accelerometers

indicate that the rotational technique should be avoided or used only

with great caution for accelerometers of that type.

3. Dual Centrifuge [4]

The dual centrifuge was developed to generate large amplitudes of

acceleration in the frequency range from 0.5 Hz to about 30 Hz. As

shown in Figure 3, it consists essentially of a small turntable mounted

on a large one, each turning in a horizontal plane. The accelerometer

is mounted on the small table with its sensitive axis in a horizontal

plane. When the turntables are rotating with constant angular velocities,

the seismic mass in the accelerometer responds to a sinusoidally varying

component of the centrifugal force field generated by the rotation of

the large table. A system of pulleys and timing belts is arranged so that the small turntable has zero absolute angular velocity in inertial

space at all times (its motion is like that of the connecting rods for

the drivewheels of a steam locomotive). The equation of motion of the

seismic mass of the accelerometer is the same as for sinusoidal linear

motion. Due to the character of the motion, the accelerometer is also

subjected to transverse acceleration during each cycle and the output

will reflect this in its departure from the ideal. The magnitude of

the generated acceleration can be varied by locating the small turntable

at various distances from the center of the large one.

The dual centrifuge can generate accelerations of ±1 gn at 1 Hz,

increasing to ±100 gn at from 10 Hz to about 25 Hz.

4. Torsional Vibration Calibrator

This device, shown in Figure 4, was built as a generator of sinusoidal

angular motion for the calibration of angular motion sensing instruments,

such as angular accelerometers and rate gyros. Based on a similar device

used by a transducer manufacturer, it is essentially an electrically

driven torsion pendulum with its shaft vertical and two tangential

8
springs supplying the restoring torque. The calibrator is useful over

a frequency range from 0.57 Hz to 30 Hz, generating angular accelerations

up to 40 rad/s^ over most of the frequency range, depending on the

inertia of the instrument under test.

5. Shock Tube [5, 10]

Since it is extremely difficult to generate sinusoidal pressures of

known amplitude in gases, the dynamic characteristics of a pressure

transducer are generally obtained from its transient response. To

provide excitation for observation of transient response, a shock tube

has been developed that generates a pressure step function with a risetime

of less than 10~8 seconds. The shock tube, shown in Figure 5, is 20 ft. long

and is divided into two chambers, 12 ft. long and 8 ft. long, by a cellulose

acetate diaphragm. The 12 ft. section is filled with helium and the

8 ft. section with dry air, the ratio of respective absolute pressures

in these sections is set to be 2.7 to 1 over the entire range of operation

of the shock tube. The pressure of the helium is set to a value

approximately equal to the desired pressure amplitude of the step

function. Upon rupture of the diaphragm, helium pushing into the air

chamber generates a Shockwave in the air which travels the length of

the 8 ft. section, and is then reflected from the rigid end wall at

an increased pressure. The amplitude of the step function pressure to

which a pickup in the end wall is exposed can be estimated by means of

ideal gas theory from the velocity of the Shockwave, and the temperature

and pressure of the air before the diaphragm is burst. The range of

step pressures that can be generated by this shock tube is 6 psi to

1000 psi and the duration of the pressure at these values is about

4.5 milliseconds.

6. Pneumatic Step Function Calibrator [1]

The step function generated by the shock tube is not accurately known

because computation of the amplitude of the step is based on ideal gas

theory. A device, shown in Figure 6, that generates a known step function

of gas pressure (for use where the extremely rapid excitation obtainable

with the shock tube is not necessary) has been developed. The amplitude

of the step generated by this device can be measured statically.

The risetime of the generated pressure is about 0.9 milliseconds (much

longer than that of the shock tube) and the initial oscillation superimposed on the step decreases to less than 2% of the step amplitude

within 15 milliseconds. The range of pressures of this pneumatic

calibrator is 2 psi to 100 psi. The heart of the calibrator is a pneumatically operated quick opening valve which applies air pressure

from a large storage tank to the transducer under test. The tank pressure

is set to the desired value by a pressure regulator and measured by a precision dial pressure gage. Since the volume of the storage tank is more than 100 times that of the combined internal volumes of the quick

opening valve and the fixture holding the transducer, gas flow and

temperature change are held to a minimum. The pressure in the storage
tank after the step is applied to the transducer, as indicated on the

dial gage, is then the same as the amplitude of the pressure step

within about ±1%. This calibrator is most useful for the inspection

of transducers for dynamic errors at low frequency such as those due

to hysteresis.

7. Liquid Medium Step Function Calibrator [7]

A liquid medium step function calibrator (based on a design by

Dr. Daniel Johnson of NBS) has been procured. The calibrator, Figure 7,

consists of a conical valve with a long stem in a large pressure vessel.

The transducer to be tested is mounted to face a small cavity in front

of the conical valve. Application of pressure to a piston at the end of the

long stem of the conical valve causes the latter to close. Pressure

of the desired amplitude is built up in the large pressure vessel.

The transducer cavity is brought to zero psig by a bleeder valve which

is thereafter kept closed. A fast release of the pressure on the valve

step piston relieves compressive stress in the valve stem and the conical

valve begins to open. As the pressure in the transducer cavity builds

up, opening of the valve accelerates, so that a pressure step of short

risetime is applied to the transducer. As in the pneumatic step

function calibrator, the ratio of the volume of the large pressure vessel

to that of the transducer cavity is wery large. In this case, also,

static measurement of the amplitude of the pressure step within about

±0.2% is possible using a precision dial gage. By selection of cavity

size, oil viscosity and the diameter of the valve stem, a nearly optimum

step function of pressure with a risetime of less than 3 milliseconds

can be obtained at most pressures from 500 psi to 3000 psi.

This device also is most useful for the inspection of transducers for

dynamic errors at low frequency such as those caused by hysteresis.

8. Transient Recorder and Frequency Analysis Scheme [10]

If pressure transducers were linear single degree of freedom systems,

simple calculations from their responses to step pressures would yield

the frequency response characteristics. Most pressure transducers are multiple degree of freedom systems and some are nonlinear. The analysis of

such systems, even when they are perfectly linear, is not simple. A simple

scheme was devised for the wave analysis of the step function pressure

response. This scheme involves the recording of the step pressure

response of the transducer on a magnetic recorder and subsequent

repetitive playback of this transient into an electronic frequency

analyzer. In this manner the resonant frequencies of multiple degree

of freedom systems may be identified. A recorder was procured, meeting

these requirements, with an oxide-coated drum rotating at 3000 rpm.

The system has a flat response from about 1.5 kHz to 80 kHz and is

capable of recording transients with durations of 1 to 6 milliseconds

and amplitudes from about 1 mV to 10 V. A multiple head arrangement

makes possible recording and storing of four transients. Playback

occurs at a rate of 60 transients per second.

10
The frequency analyzer, a commercial item, covers the frequency range

from below 1 kHz to 300 kHz and throughout most of the range is capable

of identifying frequencies of equal amplitudes less than 1 kHz apart

as well as frequencies with amplitude ratios of 100:1, but at least

one octave apart. The recorder and the frequency analyzer are shown

in Figure 8.

To test the operation of the system, the recorder analyzer was used to

analyze the transient response of electrical analogs of multiple degree

of freedom systems. All the resonances were found and their amplitudes

determined.

9. Thermal Gradient Testing Method [8, 17]

A technique was developed to assess the effects of thermal shock applied

to the sensing elements of pressure transducers. Zero shifts observed

were found to be related to the thermal gradient developed across the

body of the transducer when its sensing end was suddenly dipped into a pool of molten Wood's metal. This relatively simple and repeatable

technique makes it possible to compare the thermal transient responses

of flush diaphragm transducers. This test set-up is shown in Figure 9.

Thirteen different flush mounted pressure transducers of seven manufacturers were tested by creating a thermal gradient in them

and recording the resultant zero shifts. A typical recording shows

these general characteristics: (1) a yery rapid change in output

reaching a peak in a second or less, (2) a more gradual shift which

reaches a peak in a time which may range from a few seconds to more than a minute, and (3) a shift in reading which remains as long as the

gradient is maintained. Examples were found in which each of these

were positive or negative. The magnitude in a few cases was small,

in many was a large fraction of the transducer's range, and in one case

well in excess of the full scale range.

10. "Life Cycling" Technique for Pressure Transducers [12, 22]

Apparatus was assembled to study the effects of the repeated application

of pressure stimuli on the performance characteristics of pressure

transducers. The equipment consisted essentially of a quick-operating

solenoid three-way valve which was energized by a cam-operated switch.

A timing motor drove the cam, which energized the valve 3000 times per

hour. A pressure stimulus of selected amplitude was thereby applied

to the transducer and then relieved, 3000 times per hour. The equipment,

shown in Figure 10, ran continuously, a totalizing counter keeping track

of the number of elapsed cycles. At prescribed intervals, cycling was interrupted and the transducer was statically calibrated to establish

its performance characteristics. Each transducer under test was subjected to one million pressure cycles in order to assess any

deterioration in its performance characteristics.

Subsequently, another durability investigation was conducted on a group

of eighteen bonded-wire strain gage pressure transducers with ranges

of to 15 psig (0 to 103 kPa) and to 100 psig (0 to 689 kPa)

11
using an improved version of a previously developed technique as shown

in Figure 11. Some of the transducers were subjected to 40 x 10"

pressure cycles at a 5-Hz rate at laboratory ambient conditions, others

were cycled at a temperature of 150 °F (65.6 °C). The largest change

in sensitivity observedwas 0.22% for a 100-psig transducer subjected

to 40 x 10° pressure cycles at 150 °F. The largest change in zero pressure output observed was 0.91% FS for the same transducer. None

of the transducers failed completely as a result of cycling at or below

full scale pressure.

11

Computation of Useful Frequency Range of Piezoelectric

Accel erometers [16]~

A study was conducted into a method for computing the useful frequency

range of piezoelectric accel erometers and a paper published. This paper

analyzes two lumped-parameter models for computing the usable frequency

range of piezoelectric accel erometers. The analyses indicate why

application of an electrical excitation to the piezoelectric element

of a mounted pickup does not, in general, give the same result as application of a mechanical acceleration to the structure on which the

pickup is mounted. Tabular results of the computations for various

sets of parameters indicate those cases for which the electrical drive

will give resonant frequency values within 2% of those for the pickup

mounted on a vibrating structure. For these parameter sets, the

electrical drive can be used as a reliable substitute.

12. Effects of High-Temperature Storage on Strain Gage Pressure

Transducers [18]"

An experimental investigation was conducted into the effects of extended

high-temperature storage on the performance characteristics of several

strain gage pressure transducers. Using the equipment shown in Figure 12,

the results of this 5-week test program indicate that changes in the

sensitivity and zero characteristics of electromechanical pressure

transducers can occur as a result of storage at temperature above

ambient laboratory conditions. In some cases these performance changes

are permanent. High-temperature soaking of some transducers before

putting them into service at elevated temperature may reduce performance

changes during their operation since some transducers were observed to

have their most drastic changes during the early portion of this

temperature-storage test.

To assure reliable performance of pressure transducers operated at

elevated temperatures for extended periods of time, the effects of the

environment on the particular transducer must be investigated, since zero shifts up to 4.5% FS were observed in this program in which the pressure

transducers were subjected to the elevated temperatures for only 5 weeks.

Some applications of transducers require that the transducer operate

reliably in elevated temperature environments for much longer periods.

12
13. Hydraulic Sinusoidal Pressure Calibrator [20]

Figure 13 shows a simple, accurate device for the sinusoidal calibration

of pressure transducers. Calibration is achieved by vibrating a liquidfilled tube on an electrodynamic vibration exciter; the

pressure transducer mounted at the base of the tube senses the

si nusoi dally varying pressure in the tube. The frequency range is 15 Hz

to 2000 Hz with a maximum obtainable amplitude of 19.5 psi (134 kPa)

peak to peak. The transducer can easily be calibrated statically in

the same device, thus permitting precise correlation between static

and dynamic calibrations. Agreement between static and dynamic

calibrations to within 0.1% has been achieved.

14. Thermal Transient Tests Using Laser [21]

A simple and repeatable testing technique was developed which makes it

practical to obtain information on the zero shift and change in

sensitivity of a pressure transducer while it is subjected to a thermal

transient generated by a mechanically chopped cw laser beam. The test

setup is shown in Figures 14 and 15. Several commercial, flush

diaphragm, pressure transducers with ranges up to 50 psi (345 kPa) were tested and showed zero shifts and changes in sensitivity of the

order of 20% FS due to thermal transients with power densities up to

10 W/cm2 . The transducer under test can be pressure cycled while it

is irradiated. In this way, zero shifts and sensitivity changes may be

directly displayed in a procedure which requires a testing time of only

about one minute.

15. Thermal Transient Test for Piezoelectric Accel erometers [23, 27]

A simple, inexpensive method was developed for determining the effects

of thermal transients on the zero output and sensitivity of piezoelectric

accel erometers. Thermal transient stimuli are generated by an incandescent lamp and can be made to heat the top or side of the test

accel erometer. The test setup is shown in Figure 16. Fourteen

commercial accel erometers were tested using this technique. Zero shifts

with magnitudes as high as 640 gn were observed. Zero shifts of up to

2% of full scale resulted from 1-s duration transients, and up to 7% of

full scale from 15-s transients. These results were obtained at a radiation power density of 1.8 W/cm2 . No changes of accelerometer sensitivity

exceeding experimental uncertainties were noted as a result of the thermal

transients used.

16. Vibratory Phenomena in Li quid- Filled Cylinder [28]

A theoretical study was conducted in support of a dynamic pressure

calibration technique involving liquid media. By making appropriate

physical approximations and idealizations, a theoretical explanation was found for a vibratory phenomenon observed in calibrating pressure

transducers inside thin liquid-filled cylinders. The theoretical

explanation required proving the equivalence of two initial -boundary

problems which define the vibratory phenomenon. A short, general and

complete proof of this equivalence is given.

13
17. Flashbulb Thermal Transient Test Method [33]

A test method for evaluating the effects of short-duration, thermal

radiant-energy transients on pressure-transducer response is 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. The original

setup is shown in Figure 17, and an improved version in Figure 18.

The method is intended to serve as an initial screening test. 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 2

, with durations of about 37 ms , have been generated using No. 22

flashbulbs. In tests with No. 22 bulbs, 25 commercial pressure

transducers have shown zero shifts ranging from 0.4% to about 400%

of the full-scale output.

18. Dynamic Pressure Calibration Source [35]

A dynamic pressure source is described for producing sinusoidally

varying pressures of up to 34 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

sinusoidally varying voltage. Figure 19 shows the test setup. 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-Stoke dimethyl

siloxane working fluid in order to extend the useful frequency range

to higher frequencies than would be provided by an undamped system.

19. Dynamic Pressure Calibrations at High Static Pressures [37]

Two dynamic pressure sources were developed for the calibration of "pogo"

pressure transducers used to measure oscillatory pressures generated

in the propulsion system of the space shuttle. Rotation of a mercuryfilled tube in a vertical plane at frequencies below 5 Hz generates

sinusoidal pressures up to 48 kPa, peak-to-peak; vibrating the same mercury-filled tube sinusoidally in the vertical plane extends the

frequency response from 5 Hz to 100 Hz at pressures up to 140 kPa,

peak-to-peak. The sinusoidal pressure fluctuations can be generated

by both methods in the presence of high (static) pressures (bias) up

to 55 MPa. The sources are shown in Figures 20 and 21.

Calibration procedures are given in detail for the use of both sources.

The dynamic performance of selected transducers was evaluated using

these procedures; the results of these calibrations are presented.

Calibrations made with the two sources near 5 Hz agree to within 3% of

each other.

14
20. Thermal Transient Protection for Pressure Transducers [41 , 33]

An experimental investigation was conducted to evaluate protective

diaphragm coatings as a means to reduce the effects produced by thermal

radiant-energy transients on pressure-transducer response.

A series of tests was carried out to investigate the effects of a variety of protective coatings on the amount and rate of thermal energy

transmission through thin metal disks (used to simulate transducer

diaphragms) as revealed by measurements of the disk back-side temperature.

The temperature histories of both bare and protected disks were measured

with thermocouples during and after exposure of the disks to thermal

radiant-energy transients (of approximately 2 J/cm2 at the disk)

generated by No. 22 photographic flashbulbs. Protective coatings

investigated include various tapes, greases, and room-temperaturevulcanizing rubbers (RTVs).

Based on the results from these tests, the effectiveness of nine selected

coatings in reducing thermally-induced zero shifts of four types of

pressure transducers was investigated. In these tests, a pair of

transducers -- one protected and the other unprotected, but otherwise

nominally identical -- were exposed to a thermal radiant-energy transient

as described above. The resulting zero shift was measured and taken as an index of coating effectiveness.

The effect of the mass of the coatings on transducer dynamic response

was investigated by means of a shock tube in which a protected and

unprotected pair were simultaneously exposed to a pressure step of

approximately 280 kPa (40 psi). Also, the effect of selected coatings

on transducer acceleration sensitivity was investigated by monitoring

the outputs of pairs of transducers mounted on a vibration exciter.

Test results indicate the validity of the simulated diaphragm test as

a predictor of protection effectiveness. Results from both disk and

transducer tests show that some coating combinations appear to be an order of magnitude more effective than others in delaying and reducing

zero shift. Coatings of multi -layer black tape, red RTV silicone

rubber, and "heat sink" compound appear most effective.

Silicone grease is found least effective, while single-layer black

tape appears to produce results ranging from s/ery limited protection to

actual degradation of response, based on the limited sampling carried

out in this investigation.

Applications of Project Results

At the time of this report, the following users of transducer test methods

originating from the NBS Interagency Transducer Project have been reported

Earth's Field Dynamic Calibrator Naval Air Test Center

for Accel erometers Navy Metrology Engineering Center

Sandia Laboratories

Bendix Corporation

15
Dual Centrifuge for Accel erometers

Shock Tube for Pressure Transducer

Evaluation

Available Commercially from

Gen i sco Schaevitz Engineering

Naval Proving Ground

NASA Marshall Space Flight Center

Naval Ship Research & Development

Center

Pneumatic Step Function Pressure

Calibrator

Thermal Transient Tester for

Pressure Transducers

Dynamic Pressure Calibrator

Dynamic Pressure Calibrator at

High Static Pressures

Naval Air Test Center

NASA Langley Research Center

Sandia Laboratories

Air Force Armament Development

and Test Center

General Motors Research Laboratory

Wright Air Development Center

Sandia Laboratories

Naval Weapons Center

Lawrence Livermore Laboratory

Air Force Armament Development

and Test Center

NASA Langley Research Center

NASA Marshall Space Flight Center

Servonic Division, Gulton

Rockwell Corporation

16
Publications

The following formal publications have resulted from NBS Interagency

Project activities since 1962.

1. Lederer, P. S., Step Function Pressure Calibrator, U.S. Patent

#3,034,332 (May 15, 1962).

2. Lederer, P. S., General Characteristics of Linear Strain Gage

Accel erometers Used in Telemetry, NBS Tech. Note 150 (June 1962)

[out of print].

3. Smith, R. 0. and Hilten, J. S., Low Frequency Calibration of

Spring-Mass Accel erometers, 3rd Transducer Workshop, Telemetry

Working Group, National Bureau of Standards, Gaithersburg, Md.

(June 1962).

4. Smith, R. 0, Willis, E. A., and Hilten, J. S., A Dual Centrifuge

for Generating Low-Frequency Sinusoidal Accelerations, J. Res.

Nat. Bur. Stand. (U.S.), 66C , No. 4, 357-362 (1962).

5. Schweppe, J. L., et al . , Methods for the Dynamic Calibration of

Pressure Transducers, NBS Mono. 67 (December 1964) [out of print].

6. Lederer, P. S., Some Aspects of Transducer Calibration Techniques,

4th Transducer Workshop, Telemetry Working Group, Wright Air

Development Center, Ohio (June 1964).

7. Smith, R. 0., A Liquid Medium Step Function Pressure Calibrator,

J. of Basic Eng. 3 Trans. ASME 86D, No. 4, 723 (December 1964).

8. Horn, L., The Response of Flush Diaphragm Pressure Transducers to

Thermal Gradients, 20th Annual ISA Conference, Los Angeles, Calif.,

Paper 13.3-4-65 (October 1965).

9. Lederer, P. S. and Hilten, J. S. Earth's Field Static Calibrator

for Accel erometers, NBS Tech. Note 269 (February 1966).

10. Lederer, P. S., Methods for Performance-Testing of Electromechanical

Pressure Transducers, NBS Tech. Note 411 (February 1967) [NTIS: TN 411]

11. Lederer, P. S., Performance-Testing Pressure Transducers, Instruments &

Control Systems 40, No. 9, 93 (September 1967).

12. Lederer, P. S., "Life Cycling" Tests on Several Strain Gage Pressure

Transducers, NBS Tech. Note 434 (October 1967) [NTIS: TN 434].

13. Hilten, J. S., The National Bureau of Standards Interagency Project -- A Progress Report, 5th Transducer Workshop, Telemetry Working Group,

National Bureau of Standards, Gaithersburg, Md. (October 1967).

17
14. Lederer, P. S., NBS Interagency Transducer Project, NBS Tech. Note 469

(October 1968).

15. Lederer, P. S., Pressure -- Introduction and State-of-the-Art,

Book, ISA Transducer Compendium, Second Edition, Part 1, Ed.

G. F. Harvey, pp. 5-8 (Plenum Publishing Corp., New York, N.Y., 1969).

16. Newman, N., Considerations in Computing the Useful Frequency Range

of Piezoelectric Accel erometers, NBS Tech. Note 487 (July 1969)

[NTIS: TN 487].

17. Horn, L., Thermal Gradient Effects on Thirteen Flush Mounted Pressure

Transducers, NBS Tech. Note 490 (August 1969) [NTIS: TN 490].

18. Williams, R., The Effects of Extended High-Temperature Storage on the

Performance Characteristics of Several Strain Gage Pressure Transducers,

NBS Tech. Note 497 (October 1969) [NTIS: AD 695821].

19. Hilten, J. S., Accelerometer Calibration with the Earth's Field Dynamic

Calibrator, NBS Tech. Note 517 (March 1970) [NTIS: PB 190072].

20. Hilten, J. S., Lederer, P. S., and Sethian, J. D., A Simple Hydraulic

Sinusoidal Pressure Calibrator, NBS Tech. Note 720 (April 1972)

[GP0: SN003-003-00989-0, $0.65].

21. Lederer, P. S. and Hilten, J. S., A Laser Technique for Investigating

the Effects of Thermal Transients on Pressure Transducer Performance

Characteristics, NBS Tech. Note 723 (May 1972) [NTIS: C0M-72-50535].

22. Lederer, P. S. and Hilten, J. S., Durability Investigation of a Group

of Strain Gage Pressure Transducers, NASA CR 120953 NBS Report 10975

(December 1972).

23. Lederer, P. S., Experimental Study of the Effects of Thermal Transients

on the Performance Characteristics of the Piezoelectric Accel erometers -- Progress Report September 15, 1972 to April 15, 1973, NBSIR 73-230

(July 15, 1973) [out of print].

24. Lederer, P. S., Development of a Dynamic Pressure Calibration Technique -- Progress Report June 15, 1973 to September 15, 1973, NBSIR 73-290

(October 15, 1973) [NTIS: COM-74-10974]

25. Hilten, J. S. and Lederer, P. S., Space Shuttle Pogo Pressure Measuring

System -- Progress Report January 15, 1973 to September 15, 1973,

NBSIR 74-562 (July 15, 1974).

26. Lederer, P. S., Transducers in the Real World, Joint Measurement

Conference, National Bureau of Standards, Gaithersburg, Md. (November 1974)

27. Vezzetti, C. F. and Lederer, P. S., An Experimental Technique for the

Evaluation of Thermal Transient Effects on Piezoelectric Accel erometers,

NBS Tech. Note 855 (January 1975) [GP0: SN003-003-01371-4, $1.05].

18
28. Kraft, Richard, Note on a Vibratory Phenomenon Arising in Transducer

Calibration, NBS Tech. Note 856 (February 1975) [GPO: SN003-003-01 371-4,

$0.65]. (A theoretical analysis referring to work reported in Items 35

and 37).

29. Lederer, P. S. and Hilten, J. S., NBS Interagency Transducer Project -- Progress Report July 1, 1974 to September 30, 1974, NBSIR 75-654

(February 20, 1975) [NTIS: C0M-75-1 0367]

.

30. Lederer, P. S., NBS Interagency Transducer Project -- Report on Activities, 8th Transducer Workshop, Telemetry Group, Dayton, Ohio

(April 1975).

31. Vezzetti, C. F., Hilten, J. S., and Lederer, P. S., Development of a Dynamic Pressure Calibration Technique -- Progress Report February 15, 1974

to August 15, 1974, NBSIR 75-708 (June 5, 1975) [NTIS: COM-75-1081 7]

.

32. Lederer, P. S., Hilten, J. S., and Vezzetti, C. F., NBS Interagency

Transducer Project -- Progress Report October 1, 1974 to December 31, 1974,

NBSIR 75-732 (June 27, 1975) [NTIS: C0M-75-11022]

.

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

A Test Method for Determining the Effect of Thermal Transients on Pressure-Transducer Response, NBS Tech. Note 905 (April 1976)

[GPO: SN003-01610-1, $1.10].

34. Lederer, P. S. and Hilten, J. S., NBS Interagency Transducer Project -- Progress Report January 1, 1975 to June 30, 1975, NBSIR 76-1038

(April 1976) [NTIS: PB-25-1918].

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

A New Dynamic Source for the Calibration of Pressure Transducers,

NBS Tech. Note 914 (June 1976) [GPO: SN003-003-01610, $1.10].

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

NBS Interagency Transducer Project -- Progress Report July 1, 1975 to

December 31, 1975, NBSIR 76-1060 (June 1976) [NTIS: PB-256328]

.

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

Development of Dynamic Calibration Methods for Pogo Pressure Transducers,

NBS Tech. Note 927 (November 1976) [GPO: SN003-003-01 683-7, $1.15].

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

NBS Interagency Transducer Project -- Progress Report #5, January 1, 1976

to June 30, 1976, NBSIR 76-1144 (November 1976) [NTIS: PB-259243].

39. Lederer, P. S., Pressure Transducer Evaluation, Book, Indwelling and

Implantable Pressure Transducers (CRC Press, Cleveland, Ohio, 1977).

40. Lederer, P. S., An Overview of the Performance Characteristics of Sensory

Transducers, Workshop on Production Readiness, Purdue University, West

Lafayette, Indiana (September 1977).

19
41. Hi! ten, J. S., Vezzetti, C. F., Mayo-Wells, J. F. s and Lederer, P. S.,

Experimental Investigation of Means for Reducing the Response of

Pressure Transducers to Thermal Transients, NBS Tech. Note 961

(January 1978) [GPO: SN003-003-01875-9, $2.30].

42. Hi 1 ten, J. S., Vezzetti, C. F., Mayo-Wells, J. F., and Lederer, P. S.,

Experimental Investigation of Drill -Bit Wear, NBSIR 78-1423

(February 1978) [NTIS: PB-278618].

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

Bibliography and Brief Review of Literature on Machine-Tool Measurements

for Automatic Control, NBSIR 78-1424 (April 1978).

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

Loose-Particle Detection in Microelectronic Devices, NBSIR 78-1590

(NASA) (January 1979).

In addition, from 1952 to 1969, 71 NBS reports were published, dealing

with evaluations of selected commercial transducers (53 publications)

or with preliminary accounts of test methods (18 publications). All of

these publications are obsolete. Most are out of print or were superseded by the formal publications listed above.

Acknowledgment

The NBS Interagency Transducer Project and its accomplishment resulted

from the dedication, inspiration and hard work of a number of people

through the years. It would not be fair to try to list them all lest someone is overlooked. It is fitting, however, to recognize the

efforts of Raymond 0. Smith, who led the project from its inception

until his retirement in 1964.

20
Figure 1. Earth's field static calibrator for accelerometers. Shown are the

dividing head, surface plate, and reference level, as well as the

precision right-angle bracket on which the accelerometer is mounted,

21
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23
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transducer (mounted on horizontal boom), measuring microscope (for

static calibration of displacement transducer). An angular accelerometer (to be calibrated) is mounted on the oscillating table of

the calibrator.

24
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26
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27
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29
Figure 10. Equipment for cycling of pressure transducers to assess their dur- ability. Counters indicate cumulative number of cycles of full- scale pneumatic pressure applied to test transducers

30

I
Figure 11. Improved equipment for cycling of pressure transducers. Using this

equipment, the durability of a group of pressure transducers was investigated while the transducers were subjected to 40,000,000

pressure cycles.

31
Figure 12. Experimental set-up used for an investigation of the effects of

high-temperature storage on the performance characteristics of

pressure transducers.

32
Figure 13. Liquid-medium sinusoidal pressure calibrator, with transducer to be

calibrated, is shown mounted on an electrodynamic vibration exciter.

33
Figure 14. Experimental set-up for thermal transient tests on pressure transducers using a continuous wave laser.

34
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Figure 16. Experimental set-up for investigation of effects of thermal transients on performance of piezoelectric accelerometers showing radiant heat lamp and

shutter with test-accelerometer side exposed to thermal transient.

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Figure 21. The windmill source for the generation of low frequency pressure

variations, consisting of the closed-tube column mounted on the

windmill apparatus.

41
NBS-114A (REV. 9-78)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO

TN 1110

4. TITLE AND SUBTITLE

NBS Interagency Transducer Project

1951-1979 -- An Overview

5. Publication Date August 1979

,„,_

7. AUTHOR(S)

Paul S. Lederer

8. Performing Organ. Report No.

.I'll I.IIMI .1 II II Mil 9. PERFORMING ORGANIZATION NAME AND ADDRESS », Profr<*/Tasfc/Woffc ttsit Ho.

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

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Same as Item No. 9

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Final

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1 "•

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Supersedes NBS Technical Note 469, published October 1968.

I

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literature aurvey, mention it here.) Between 1951 and 1979, the National Bureau of Standards was engaged in a continuing

project to study the performance of sensory transducers, primarily those used in

telemetry. This project has been supported by agencies of the Defense Department and

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separated by semicolons)

Dynamic calibration; evaluation; Interagency Transducer Project; performance

characteristics; telemetry; transducer

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