IMBSIR 76-1145

Interlaboratory Comparison of

Force Calibrations Using ASTM

Method E74-74

Phase I

R. W. Peterson and R. L. Bloss

Engineering Mechanics Section

Mechanics Division

Institute for Basic Standards

National Bureau of Standards

Washington, D C. 20234

August 1976

Summary Report

Covering Period 6/1/74 to 8/1/75

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

NBSIR 76-1 145

INTERLABORATORY COMPARISON OF

FORCE CALIBRATIONS USING ASTM

METHOD E74-74

Phase I

R W. Peterson and R. L. Bloss

Engineering Mechanics Section

Mechanics Division

Institute for Basic Standards

National Bureau of Standards

Washington, D C. 20234

August 1976

Summary Report

Covering Period 6/1/74 to 8/1/75

U S. DEPARTMENT OF COMMERCE, Elliot L. Richardson, Secretary

Edward O. Vetter, Under Secretary

Dr. Betsy Ancker-Johnson, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Acting Director
• ••

. ^

V

'

: ,
CONTENTS

Page

1. SCOPE 1

2. PROGRAM DESCRIPTION 2

3. TEST PROCEDURE 2

4. ANALYSIS OF DATA 2

5. SUMMARY OF RESULTS 18

6. CONCLUSIONS 26

7. RECOMMENDATION FOR FUTURE PROGRAM PHASES 26

8. APPENDIX A A1

l
LIST OF FIGURES

Page

la. OMNITAB analysis of Round-Robin data, ASTM F.74-74. 3

lb. OMNITAB analysis of Round-Robin dated, ASTM E74-74. 4

2. Difference between curve values and NBS base value in

compression. 6

3. Difference between curve values and NBS base value in

tension. 7

4. Difference between curve values and NBS base value in

compression. 8

5. Difference between curve values and NBS base value in

tension. 9

6. Difference between curve values and NBS base value in

compression. 10

7. Difference between curve values and NBS base value in

tension. 11

8. Difference between curve values and NBS base value in

compression. 12

9. Difference between curve values and NBS base value in

tension. 13

10. Difference between each calibration and the average value

at capacity load for 500 lbf capacity load cells. 19

11. Difference between each calibration and the average value

at capacity load for 5000 lbf load cell. 20

12. Difference between each calibration and the average value

at capacity load for 20 000 lbf load cell. 21

13. Difference between each calibration and the average value

at capacity load for 100 000 lbf capacity load cells. 22

14. Difference between each calibration and the average value

at 50 percent of capacity load for load cells of Package 1 in compression. 23

15. Difference between each calibration and the average value

at 50 percent of capacity load for load cells of Package 2 in tension. 24

ii
LIST OF TABLES

Page

1. Comparison of Calibration Data for 500 lbf Capacity Cells. 14

2. Comparison of Calibration Data for 5000 lbf Capacity Cell. 15

3. Comparison of Calibration Data for 20 000 lbf Capacity Cell. 16

4. Comparison of Calibration Data for 100 000 lbf Capacity Cell. 17

5. Summary of Calibration Results. 25

iii
-
INTERLABORATORY COMPARISON OF

FORCE CALIBRATIONS USING ASTM METHOD E74-74

Phase I

R. W. Peterson and R. L. Bloss

ABSTRACT

This report covers the first phase of an intercomparison of force calibrations coordinated by the National Bureau of Standards in

conjunction with Committee E28.01 of the American Society for Testing and Materials. Results

obtained show that the provisions of ASTM

Method E74-74, "Standard Methods of Calibration

of Force-Measuring Instruments for Verifying

the Load Indication of Testing Machines" can be met by a variety of calibration laboratories. In general, uncertainties computed

from the data are of the magnitude expected

based upon the NBS results. An important byproduct of the program is the mechanism for

self-evaluation by each laboratory of its own

force calibration capability.

Key Words: Force; force calibration; interlaboratory comparison; load cell; static force.

1. SCOPE

This report covers the first phase of an intercomparison of force

calibrations coordinated by the National Bureau of Standards in conjunction with Committee E28.01 of the American Society for Testing and

Materials. The objectives of the program are to evaluate ASTM E74-74,

"Standard Methods of Calibration of Force-Measuring Instruments for

Verifying the Load Indication of Testing Machines," and to familiarize

calibration laboratories with its contents. An important by-product

of the program is the mechanism for self-evaluation by each laboratory

of its own force calibration capability.
2.

PROGRAM DESCRIPTION

At the conception of this program, approximately thirty organizations having force calibration capability expressed an interest in

participating. These laboratories represent large and small industrial

companies, load cell and proving ring manufacturers, DOD and NASA con- tractors, and federal government agencies. In order to identify problems

and provide an intermediate evaluation of the program, an introductory

phase was initiated. This first phase is the subject of this report.

Six laboratories, representing a variety of functions and capabilities, participated in Phase I. Two packages of force-measuring instruments were circulated among the six laboratories and NBS. Package One

consisted of 500 lbf* and 5000 lbf capacity load cells with an indicator.

Package Two consisted of 20 000 and 100 000 lbf capacity load cells with

an indicator. NBS performed calibrations on each package before and

after they were calibrated by each of the other laboratories. In order

that each laboratory could quickly evaluate the results of their calibration, a preliminary data analysis was furnished which compared their

data to the before and after NBS calibrations. An example is shown in

Figure 1. These data are further examined in this report and will also

be included as part of the larger study now underway.

3.

TEST PROCEDURE

The participants were requested to calibrate each of the load cells

in strict accordance with Section 6 of ASTM Method E74-74.** The load

cells were to be treated as tension and compression devices for which

calibration equations were to be established. It was further requested

that information on the calibration standards and procedures used be

submitted to NBS as part of the calibration record. The information

requested is shown in Appendix A.

4.

ANALYSIS OF DATA

According to ASTM E74-74, a "continuous-reading" device is calibrated by sampling load measurements over its range in order to describe

the f orce-to-def lect ion relationship. The calibration data are usually

fitted to a second-degree curve of the form D = A + BL + CL 2 by the

method of least squares. In this equation D is the deflection, L is the

* Since the rated capacity of the devices used in this study and the

nominal load values were given in U. S. Customary units (lbf), these

units are retained throughout this report. Conversion to SI units can be made using the relationship 1 lbf = 4.44822 Newtons.

** Can be obtained from The American Society for Testing and Materials,

1916 Race Street, Philadelphia, Pa. 19103.

2
ZAPACITY 100,000 LRF COMPRESSION ANO TENSION FEBRUARY II,

A S T M CALIBRATION CURVE DATA - COMPRESSION

A CALIBRATION EQUATION OF THE FORM,

DEFLECTION = (A) (RML0AD1 + (C)ILOAD SQUARED)

WAS FITTED TO THE OBSERVED DATA BY THE METHOD OF

LEAST SQUARES. THE COEFFICIENTS, STANDARD DEVIATION,

AND UNCERTAINTY IAS DEFINED BY A ST M METHOD E l*)-?**)

FOR THE PREVIOUS NBS CALIBRATION, THE CALIBRATION

IN YOUR LABORATORY, AND A CHECK CALIBRATION AT NBS

AFTER THE INSTRUMENT WAS RETURNED, ARE SHOWN BELOW.

A B C

(LOG FORMAT)

ST.D V . UNITS

U N C E R T . LBF

D I F F • * PERCENT

PREVIOUS NBS -2. ! I .52981

-.23349-08 1 .79 CO •— 0 .000

YOUR LABORATORY “6.29 .530175 -.59 149-08 7.86 35.6 1 -.008

NBS CHECK “2.10 • 5 2 9 B 27 -.27801-08 2.03 9.20 - . 006

The graph on PAGE 2 SHOWS The DIFFERENCE BETWEEN

YOUR CALIBRATION EQUATION (.) AMD THE PREVIOUS NBS

EQUATION (ZERO AXIS). THE NBS CHECK CALIBRATION

CURVE (») IS SHOWN FOR COMPARISON. ANY ?*S PLOTTED

ON THE GRAPH SIGNIFY TWO COINCIDENTAL CURVE VALUES.

DIFFERENCE, AT CAPACITY LOAD, FROM PREVIOUS NBS VALUE.

VALUF5 ARE FROM FITTED CURVES.

Figure la. OMNITAB analysis of Round-Robin data, ASTM E74-74.

17 71

3
A F‘. S - COLUMN IS

ORO- COLUMN 17 C • > » COLUMN | 8 (•),

NO. OF P T S . PLOTTED 100 NO. MOT PLOTTFD (OUT OF BOUNDS) 0

4 4 4 4 4- 4 s.onoo-o?4 <

3 . 0000-02+

1 . 0000 - 02 *

• •

- 1 . 0000 - 02 +

-3.0000-02+

* + 2 *

S .0000-92 + 0.0000 4 . 0000+04 8. 00 00+04 I . 200U+

COMPRESSION LOAD IN POUNDS-FORCE

Figure lb. OMNITAB analysis of Round-Robin data, ASTM E74-74.

4
load and A, B, and C are coefficients determined by the curve fitting

process. The equation of this curve is then taken as representing the

force-deflection characteristics of the device. The probable uncertainty in a measurement subsequently made with the device is assumed to

relate to the agreement of the experimental calibration readings and the

equation. The method of computing this uncertainty is given in Section 7 of E74-74. This curve fitting process was followed with the data from

each laboratory for each load cell. Using the same process, a curve was

fitted to all of the data taken at NBS with each load cell (from four to

eight sets of calibration data). The equation of this curve, the "NBS

base equation," was then used to compare with all other results. The

standard deviation used to determine the uncertainty of the base equation

is computed from the residuals of the combined data relative to the base

equation. Although a number of ways for comparing the various calibration

equations to the NBS base equations were explored, no completely satisfactory method has been found. Tables 1 through 4 show the differences at

four force values and the uncertainty values based upon the laboratory

and NBS calibrations. Base curve values are from the combined results

of from four to eight calibrations made at NBS over a period of ten

months. The values for the other laboratories are based upon one calibration. It should be noted that two 500 lbf capacity load cells were

used since one was damaged midway through the program.

The laboratory and NBS base equations cannot be considered to be

statistically different at the 99 percent confidence level unless the

difference between the curves is greater than the combined uncertainties.

This occurred in 7 of the 44 calibrations. However, this does not address

the level of uncertainty that is acceptable. The response to this question must be based upon the accuracy required of measurements to be made

with the device. Method E74-74 establishes two instrument classes based

upon the uncertainty — Class AA with an uncertainty of less than 0.05

percent of load and Class A with an uncertainty of less than 0.25 percent

of load. These classes are established for particular applications, and

other levels of uncertainty could be specified for other uses. The usefulness of a device calibrated by a particular system would then depend

upon the measurement requirements.

The d

i

of each lab

2 through 9

interval fo are not plo

fference between the equations of

oratory and the NBS base equation

. The ±2.4 o marks correspond to

r the NBS base. The uncertainties

tted, but they can be found in Tab

the individual calibrat

are also shown in Figur

the 99 percent conf iden

of the labora tory valu

les 1 through 4.

io

esce

es

ns

5
DIFFERENCE

(

PERCENT

OF

CAPACITY)

LOAD, Ibf

Figure 2. Difference between curve values and NBS base value in compression.

6
difference

(percent

of

capacity)

LOAD, I bf

Figure 3. Difference between curve values and NBS base value in tension.

7
DIFFERENCE

(PERCENT

OF

CAPACITY)

12345 *1000

LOAD, Ibf

Difference between curve values and NBS base value in compression.

8

0

Figure 4.
DIFFERENCE

(PERCENT

OF

CAPACITY)

LOAD, Ibf

Figure 5. Difference between curve values and NBS base value in tension.

9
DIFFERENCE

(PERCENT

OF

CAPACITY)

LOAD, Ibf

Figure 6. Difference between curve values and NBS base value in compression.

10
difference

(percent

of

capacity

Figure 7. Difference between curve values and NBS base value in tension.

11
DIFFERENCE

(PERCENT

OF

CAPACITY)

12
DIFFERENCE

(PERCENT

OF

CAPACITY)

LOAD, Ibf

Figure 9. Difference between curve values and NBS base value in tension.

13
TABLE 1. Comparison of Calibration Data

for 500 lbf Capacity Cells

COMPRESSION

DIFFERENCE FROM BASE CURVE UNCERTAINTY

LAB 25% 50% 75% 100% LAB LAB & BASE

LBF % CAP LBF % CAP LBF % CAP LBF % CAP LBF LBF % CAP

A(l.) -.012 -.002 -.007 -.001 -.003 -.000 .001 .000 .123 .233 .047

E(2.) .014 .003 .006 .001 -.002 .000 -.009 -.002 .195 .315 .063

H(2.) -.059 -.012 -.038 -.008 -.018 -.004 .003 .000 .122 .241 .048

K(l.) -.016 -.003 -.003 .000 .010 .002 .023 .005 .047 .157 .031

R(l.) .000 .000 .022 .004 .044 .009 .065 .013 .083 .194 .039

T (2 . ) -.027 -.005 -.041 -.008 -.055 -.011 -.069 -.014 .163 .163 .033

TENSION

A(l.) .032 .006 -.054 -.011 -.141 -.028 -.227 -.045 .081 .242 .048

E(2.) -.018 -.004 -.024 -.005 -.029 -.006 -.035 -.007 .093 .211 .042

H(2 . ) .094 .019 .208 .042 .323 .065 .437 .087 .136 .255 .051

K(l.) -.026 -.005 -.023 -.005 -.020 -.004 -.017 -.003 .068 .228 .046

R(l.) .115 .023 .042 .008 -.032 -.006 -.105 -.021 .375 .535 .107

T(2.) -.032 -.006 -.028 -.006 -.024 -.005 -.021 -.004 .053 .171 .034

(1.) Original cell

(2.) Replacement cell

14
TABLE 2. Comparison of Calibration Data

for 5000 lbf Capacity Cell

COMPRESSION

DIFFERENCE FROM BASE CURVE UNCERTAINTY

LAB 25% 50% 75% 100% LAB LAB & BASE

LBF % CAP LBF % CAP LBF % CAP LBF % CAP LBF LBF % CAP

A .15 .003 .70 .014 1.25 .025 1.80 .036 .93 2.17 .043

E -.91 -.018 -1.64 -.033 -2.37 -.047 -3.10 -.062 1.68 2.92 .058

H 1.96 .039 4.95 .099 7.95 .159 10.94 .219 1.93 3.17 .063

K -.15 -.003 -.56 -.011 -.97 -.019 -1.38 -.028 1.32 2.56 .051

R -.88 -.018 -.36 -.007 .15 .003 .67 .013 2.11 3.35 .067

T .25 .005 .81 .016 1.38 .028 1.95 .039 .89 2.14 .043

TENSION

A -L 63 -.033 -2.39 -.048 -3.15 -.063 -3.92 -.078 .94 2.67 .053

E -.10 -.002 -.39 -.008 -.68 -.014 0.96 -.019 .70 2.42 .049

H -.41 -.008 -.57 -.011 -.72 -.014 -.87 -.017 1.72 3.45 . 069

K . 11 .002 -.90 -.018 -1.92 -.038 -2.93 -.059 1.56 3.28 .066

R .15 .003 .48 .010 .82 .016 1.16 .023 1.99 3.72 .074

T -.25 -.005 -.23 -.005 -.21 -.004 -.19 -.004 1.38 3.10 .062

15
TABLE 3. Comparison of Calibration Data

for 20 000 lbf Capacity Cell

COMPRESSION

LAB

DIFFERENCE FROM BASE CURVE UNCERTAINTY

25% 50% 75% 100% LAB LAB & BASE

LBF % CAP LBF % CAP LBF % CAP LBF % CAP LBF LBF % CAP

A 4 .020 2.1 .010 .2 .001 -1.7 -.008 6.8 12.1 .061

LH -13.5 -.067 -28.7 -.144 -43.9 -.220 -59.2 -.296 6.1 11.4 .057

K 2.5 .012 4.7 .024 6.9 .034 9.1 .045 1.8 7.1 .036

R 4.3 .022 7.2 .036 10.1 .050 12.9 .065 2.6 7.8 .039

T 2.8 .014 1.9 .009 .9 .005 -.05 -.000 6.6 11.9 .060

TENSION

A

T?

-1.8 -.009 -6.9 -.034 -12 -.060 -17.1 -.085 7.5 10.8 .054

H -.5 -.002 -2.8 -.014 -5 -.025 -7.3 -.037 6.9 10.1 .051

K -.5 -.002 1 .005 2.5 .013 4.1 .020 1.6 4.9 .024

R 1.2 .006 3 .015 4.9 .024 6.8 .034 2.1 5.4 .027

T 2.7 .013 -3.6 -.018 -9.8 -.049 -16 -.080 9.4 12.7 .063

16
TABLE 4. Comparison of Calibration Data

for 100 000 lbf Capacity Cell

COMPRESSION

DIFFERENCE FROM BASE CURVE UNCERTAINTY

LAB 25% 50% 75% 100% LAB LAB & BASE

LBF % CAP LBF % CAP LBF % CAP LBF % CAP LBF LBF % CAP

A 16 .016 41 .041 65 .065 90 .090 34 64 .064

E

H

K

38 .038 113 .113 188 .188 263 .263 33 63 .063

9 .009 15 .015 21 .021 27 .027 18 48 .048

R 8 .008 23 .023 38 .038 52 .052 28 59 .059

T 9 .009 29 .029 49 .049 69 .069 36 66 .066

TENSION

A 27 .027 16 .016 6 .006 -4 -.004 60 96 .096

E

H

K

-4 -.004 30 .030 63 .063 97 .097 42 77 .077

-15 -.015 -9 -.009 -3 -.003 3 .003 15 50 .050

R 23 .023 32 .032 40 .040 48 .048 40 76 .076

T 6 .006 7 .007 9 .009 11 .011 44 80 .080

17
In an attempt to determine if there were predominate systematic

differences between the results from the various laboratories, the differences from the average of all results at capacity load were plotted in

the form of Youden graphs, with tension and compression data for one load

cell being shown on a graph. Systematic differences would be shown by

the plotted points tending to fall along a diagonal line, i.e., in the

first and third quadrants. These graphs are shown in Figure 10 through

13. Although there is some tendency towards such grouping, it is not con- clusive. This process was also used to examine the results of each test

package to determine if indicator instability was a significant problem.

These graphs. Figures 14 and 15, show no significant trend. It should

be noted that the values plotted in Figures 10 through 15 are not of the

type usually compared by means of the Youden graphs and that the number

of laboratories involved is small for such a comparison. While an indication of a strong systematic difference would have been significant,

the results shown are not considered to be conclusive.

5. SUMMARY OF RESULTS

Table 5 is a summary of the results from the participating laboratories. An all cases, the base uncertainty is larger than the smallest

uncertainty value of the participating laboratories. This is attributed

to long term drift, and other factors affecting system stability during

the course of the program. Inspection of all of the data suggests a systematic drift of most of the devices. However, since the largest

uncertainty for the NBS base equation is 0.036 percent of capacity, no attempt was made to adjust the data to account for the possible drift.

It is also noted that this uncertainty (0.036 percent of capacity) would

allow an ASTM E74-74 Class A loading range from 15 to 100 percent of

device capacity.

Although a number of the laboratory results did differ from the

NBS base equation, the significance can only be evaluated in terms of

the individual laboratory requirements. Since information for such an evaluation was not gathered as part of this program, no judgments will

be made here. As noted earlier, however, each laboratory was informed

of their agreement with NBS values shortly after their data were submitted. In some cases NBS cooperation was sought to reduce the differences .

18
PERCENT

OF

CAPACITY

TENSION

-.05 “04 -.03 -.02 -.01 .0 .01 .0 2 .03 .04

COMPRESSION

PERCENT OF CAPACITY

Figure 10. Difference between each calibration and the average value at capacity load for 500 lbf capacity load cells.

19
PERCENT

OF

CAPACITY

TENSION

Figure 11. Difference between each calibration and the average value at

capacity load for 5000 lbf load cell.
PERCENT

OF

CAPACITY

TENSION

COMPRESSION

PERCENT OF CAPACITY

Figure 12. Difference between each calibration and the average value at

capacity load for 20 000 lbf load cell.

21
PERCENT

OF

CAPACITY

TENSION

Figure 13. Difference between each calibration and the average value at

capacity load for 100 000 lbf capacity load cells.
PERCENT

OF

CAPACITY

PERCENT OF CAPACITY

500 Ibf LOAD CELL

Figure 14. Difference between each calibration and the average value at

50 percent of capacity load for load cells of Package 1 in

compression.

23
PERCENT

OF

%

CAPACITY

L

PERCENT OF CAPACITY

20,000 Ibf LOAD CELL

Figure 15. Difference between each calibration and the average value at

50 percent of capacity load for load cells of Package 2 in

tension.

24
TABLE 5. Summary of Calibration Results

Calibrations

Load Cell Loading Uncertainty (LBF) by Participating

Cap Mode Base Labs ( min-max) Laboratories

500 (a) C 0.110 0.047 - 0.123 3

500 (a) T 0.161 0.068 - 0.375 3

500 (b) C 0.120 0.043 - 0.195 3

500 (b) T 0.119 0.053 - 0.136 3

5000 C 1.24 0.89 - 2.11 6

5000 T 1.73 0.70 - 1.99 6

20,000 C 5.3 1.8 - 6.8 5

20,000 T 3.3 1.6 - 9.4 5

100,000 C 30 18 - 36 5

100,000 T 36 15 - 60 5

(a) Original Load Cell (Destroyed on 2-26 -75)

(b) Replacement Load Cell

25
6. CONCLUSIONS

Results obtained from the first phase of this program show that

the provisions of ASTM Method E74-74 can be met by a variety of calibration laboratories since no comments indicating procedural problems

were received. In general, uncertainties computed from the data are

of the magnitude expected based upon the NBS results. A significant

number of the laboratory results were statistically different from the

NBS base equation values, but the significance of this cannot be evaluated without more information on the end use of the calibration results.

The stability of load cell systems may be a problem for the second phase

of the program, although frequent calibration by NBS should permit the

data to be adjusted for time effects.

7. RECOMMENDATIONS FOR FUTURE PROGRAM PHASES

The logistical aspects of the first phase seem quite acceptable.

Since a substantial data base for the instruments has been developed,

the next phase will be conducted without returning the packages to NBS

after each laboratory calibration. As many as three laboratories will

perform calibrations on each excursion of a package.

A more satisfactory method of comparing the calibration results with

the NBS base equation is being sought.

26
APPENDIX A

ASTM FORCE ROUND ROBIN

Information Sheet for

In order to provide a comprehensive evaluation of test results, the

following information is requested for each calibration. This information,

along with your calibration data will be held in confidence by NBS.

However, if there are restrictions on furnishing some information requested,

omit that portion and make an appropriate note.

Laboratory ; Date of Calibration

Person providing this information

Force Standard (s) Employed

Serial Last Calibrated

Type MFG Number Range Uncertainty Date By

Notes

1. Types of standards include, deadweight, load cell, proving ring,

hydraulic force-multiplying system, mechanical force-multiplying

system, etc.

2. When quoting uncertainty, if given in percent, be sure to state

whether percent of load or percent of capacity of standard.

If secondary force standards (proving rings, load cells, etc.) were

employed, please indicate the type of apparatus used to apply the loads.

Hydraulic Loading Frame, capacity

Mechanical Loading Frame, capacity

Testing Machine, capacity

Other capacity

A1
page 2

If applicable, please give the force-deflection equation for each force

standard.

; serial no.

; serial no.

; serial no.

If hydraulic or mechanical force-multiplying systems were employed, please

give the nominal multiplying ratio.

; serial no.

; serial no. .

; serial no.

If ambient temperature during calibration is not shown on your data sheet,

please indicate here (average value) .

If deadweights are used, either directly or in force-multiplying systems, has

your data been compensated for the effects of local gravity and airbouyancy?

No

Yes; mathematically, or weight adjustment (refer to Section

5.1.1 of E74-74) .

Please describe describe briefly your efforts to randomize loading con- ditions as specified in Section 6.4 of ASTM E74-74.

A2
page 3

Will you furnish a formal calibration report (in the near future) as specified by section 11. of E74-74?

Yes No

We would appreciate any comments on E74-74; it's usefulness, problems,

good points or bad.

A3
NBS-1 14A (REV. 7-73)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

NBSIR 76-1145

2. Gov’t Accession

No.

3. Recipient’s Accession No.

4. TITLE AND SUBTITLE

Interlaboratory Comparison of Force Calibrations

using ASTM Method E74-74

Phase I

5. Publication Date August 1976

6. Performing Organization Code I 1

7. AUTHOR(S)

R. W. Peterson and R. L. Bloss

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Projcct/Task/Work Unit No. 1 213Q 141 1 11. Contract/Grant No.

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

Same as above

, 13. Type of Report & Period Covered Summary

6/1/74 to 8/1/75

14. Sponsoring Agency Code

1

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

This report covers the first phase of an intercomparison of force calibrations

coordinated by the National Bureau of Standards in conjunction with Committee E28.01

of the American Society for Testing and Materials. Results obtained show that the

provisions of ASTM Method E74-74, "Standard Methods of Calibration of Force-Measuring

Instruments for Verifying the Load Indication of Testing Machines" can be met by a variety of calibration laboratories. In general, uncertainties computed from the

data are of the magnitude expected based upon the NBS results. An important byproduct of the program is the mechanism for self-evaluation by each laboratory of

its own force calibration capability.

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

)

Force; force calibration; interlaboratory comparison; load cell; static force.

18. AVAILABILITY fyl Unlimited 19. SECURITY CLASS

(THIS REPORT)

21. NO. OF PAGES

For Official Distribution. Do Not Release to NTIS

UNCLASSIFIED 34

1 Order From Sup. of Doc., U.S. Government Printing Office Washington, D.C. 20402. SD Cat. No. 03

20. SECURITY CLASS

(THIS PAGE)

22. Price

[XI Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151 UNCLASSIFIED $4.00

USCOMM.DC 29042-P74