library, »•»• Bldg

SEP 6 1963

^ecknical ^iote 195

REPORT ON TECHNICAL

INVESTIGATION OF ODOMETERS

DONALD R. MACKAY

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress,

March 3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and maintenance of the national standards of measurement and the provision of means

and methods for making measurements consistent with these standards; the determination of

physical constants and properties of materials; the development of methods and instruments

for testing materials, devices, and structures; advisory services to government agencies on

scientific and technical problems; invention and development of devices to serve special needs

of the Government; and the development of standard practices, codes, and specifications. The

work includes basic and applied research, development, engineering, instrumentation, testing,

evaluation, calibration services, and various consultation and information services. Research

projects arc also performed for other government agencies when the work relates to and supplements the basic program of the Bureau or when the Bureau's unique competence is required.

The scope of activities is suggested by the listing of divisions and sections on the inside of

the back cover.

Publications

The results of the Bureau's research arc published either in the Bureau's own series of

publications or in the journals of professional and scientific societies. The Bureau publishes

three periodicals available from the Government Printing Office: The Journal of Research,

published in four separate sections, presents complete scientific and technical papers; the Technical News Bulletin presents summary and preliminary reports on work in progress; and (he

Central Radio Propagation Laboratory Ionospheric Predictions provides data for determining

the best frequencies to use for radio communications throughout the world. There are also

five series of nonperiodical publications: Monographs, Applied Mathematics Scries, Handbooks.

Miscellaneous Publications, and Technical Notes.

A complete listing of the Bureau's publications can be found in National Bureau of Standards Circular 460, Publications of the National Bureau of Standards, 1901 to June 1947 ($1.25),

and the Supplement to National Bureau of Standards Circular 460, July 1947 to June 1957

(SI. 50), and Miscellaneous Publication 240, July 1957 to June 1960 (includes Titles of Papers

Published in Outside Journals 1950 to 1959) ($2.25); available from the Superintendent of

Documents, Government Printing Office, Washington 25, D.C.
NATIONAL BUREAU OF STANDARDS

*£ecknical <

Ylote 195

ISSUED AUGUST 6, 1963

REPORT ON TECHNICAL

INVESTIGATION OF ODOMETERS

Donald R. Mackay

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 25, D.C. Price 25 cents

Contents

Page

1. Introduction 1

2. Instrument Calibration Course 1

3. Standard Test Instrument 2

4. Instrument Calibration 2

5. Additional Testing Instruments 4

6. Safety Precautions 5

7. The Testing of Automobile Odometers Using the

Fifth Wheel 5

7.1. Test Courses 5 7.2. Test Vehicles 6

7.3. Test Procedures and Observations 6

7.4. Special Tests 8

8. Test Results 9

8.1. Odometer Accuracy 9

8.2. Effect of Variables 10

8.3. Precision of Test 11

8.4. Test Conclusions 11

9. The Testing of Truck Odometers Using the

Fifth Wheel 12

9.1. Test Courses 12

9.2. Test Vehicles 12

9.3. Test Procedures and Observations 12

9.4. Test Results 12

9.5. Effects of Variables 13

9.6. Precision of Tests 13

in
Page

10. Road Tests 13

10. 1. Test Procedures and Observations 13

10.2. Test Results 14

10.3. Test Conclusions 15

11. Simulated-Road Tests 15

11. 1. Device Calibration 15

11.2. Tests Conducted 15

11.3. Test Procedures and Observations 16

11.4. Test Results 16

11.5. Test Conclusions 17

12. Wheel Tests 17

12. 1. Test Procedures and Observations 18

12.2. Test Results 18

12.3. Test Finding 19

12.4. Test Conclusion 19

13. Conclusions 19

Appendix I. Summary of Automobile Odometer Accuracy

Tests (Using Fifth-Wheel Device) 21

Appendix II. Summary of Truck Odometer Accuracy

Tests (Using Fifth-Wheel Device) 23

Appendix III. Proposed OWM Specifications for

"Fifth-Wheel" Testing Fquipment 24

Appendix IV. Proposed OWM Specifications for

Simulated-Road Testing Equipment 2 6

IV
Report on Technical Investigation of Odometers

Donald R. Mackay

A technical investigation of the accuracy of

vehicle odometers was conducted by the Office of

Weights and Measures. This report describes

(1) the determination of the accuracy of odometers,

(2) the identification of the factors that affect accuracy, and (3) the development of testing equipment

and procedures to be used in the testing of odometers. Included in the investigation were fifthwheel tests, road tests, wheel tests, and simulatedroad tests. Each type of test is described, and the

results discussed.

1. Introduction

At the request of the Committee on Specifications and Tolerances

of the National Conference on Weights and Measures, the Office of

Weights and Measures undertook a technical investigation of odometers

on rental automobiles and trucks. The objectives of the study were

(1) to determine the accuracy of odometers on rent vehicles under

standard test conditions, (2) to identify the factors that affect accuracy

under the test conditions, (3) to devise and prove testing equipment and

procedures, and (4) to prepare recommendations to the committee

appropriate amendments to existing technical requirements. This

report will cover items (1), (2), and (3).

2. Instrument Calibration Course

In order to select and to calibrate from time to time a standard

test instrument, a 1-mile calibration course was measured and marked

on a new, unopened section of a freeway in Washington, D. C. This

course, in the center of the outside lane on a fairly straight section of

the freeway, was measured with a calibrated 100-foot steel tape held

flat on the pavement under the prescribed 10-pound tension. A check

1
measurement of the course differed from the original measurement by

less than 1 part in 20, 000.

3. Standard Test Instrument

A commercially available device, known as a "fifth wheel, " was

selected as the standard test instrument (figure 1). This was a

length-measuring instrument consisting of a carefully balanced rubbertired (pneumatic) wheel, approximately bicycle size, mounted through

sealed, nearly friction-free ball bearings to a rigid frame. The frame

was hinge-connected to an adjustable clamp which was used to attach

the device to the rear bumper of an automobile. Between the frame

and the bumper clamp were two over- center springs that held the unit,

when it was not in use, in a vertical position above the bumper and that

provided spring-loaded road contact when the wheel was in operating

position. Specifications for such a testing device are found in Appendix

III. A fifth wheel may be equipped with either a mechanical or an

electrical counter connected at the hub. The device used in this investigation was specially modified to accommodate a connector for a

mechanical counter on one side and a connector for an electrical

counter on the other side. The mechanical counter (figure 2) indicated

digitally tens of miles, miles, tenths, and hundredths of miles and,

with a small analog indicator, thousandths of miles. The electrical

indicator, using as its 12 -volt power source either a cigarette-lighter

connector or two 6-volt dry cells connected in series, indicated digitally miles, tenths, hundredths, and thousandths of a mile, with an

easily discernible, visible, and audible signal, approximately 0. 0005

mile. The electrical indicator was a high-speed electromagnetic

counter fed by a make-and-break type impulse generator at the wheel.

The air pressure in the fifth-wheel tire was maintained at

25 psi (gage) ±0. 5 psi, as indicated on a calibrated, dial-type master

tire-pressure gage.

4. Instrument Calibration

With the fifth wheel connected to an automobile, a number of twodirection runs (north and south) were made over the calibration course

as follows: (1) The wheel was positioned so that the center of the hub

was directly over the starting point, (2) the wheel was lifted from the

pavement and rotated by hand until generator contact was just made,

(3) the wheel was lowered carefully without additional rotation until
Figure 1. Fifth Wheel in Test Position

Figure 2. Fifth Wheel with Mechanical Counter

3
pavement contact was reestablished, (4) the counter was zeroed, and

(5) the calibration run was begun.

During a calibration run the vehicle driver maintained, as closely as practicable, the position on the roadway that would keep the fifth

wheel directly over the measured course. Calibration runs were made

at various speeds as indicated by the automobile speedometer. The

results of the calibration runs were as follows:

Indicated Speed Fifth-Wheel Indication Apparent Error

10 mph 1.005 miles +0.005 mile/mile

30 mph 1. 004 miles +0. 004 mile /mile

50 mph 1.003 miles +0. 003 mile /mile

In order to establish "standard" conditions for recalibration runs,

a fifth-wheel "calibration" speed of 30 miles per hour indicated was

empirically established. At 30 mph, original calibration runs provided, over the 1-mile measured course, a counter indication of 1. 004

miles based on six successive runs with no variability between runs.

The fifth wheel was also recalibrated at various times during the

testing program either to check the original data or to determine new

calibration correction factors. A calibration determination made on

June 1, 1962, reaffirmed the original data. However, another determination made on August 30 and 31, after almost 3000 miles of use, indicated a reading of 1. 0045 for the measured mile. The tire wear

during this three-month period of use had reduced the mean effective

circumference of the fifth wheel, causing an additional indication of

0. 0005 mile.

The calibration data provided the correction factors which could

be applied to the fifth-wheel counter indications resulting from actual

vehicle odometer tests. The corrected indication could then be used

to obtain the absolute distance traveled and, thus, the absolute error

of the odometer.

5. Additional Testing Instruments

Although the fifth wheel was the major piece of equipment used

during the investigation, two small instruments were also used in

determining test information concerning the vehicles --an air-pressure

gage and a tire-tread depth gage. The air-pressure gage was used to
measure the air pressure in the rear tires and to adjust the pressure

to the level recommended by the automobile tire manufacturer. Four

common tire-pressure gages were purchased, as well as a master

tire-pressure gage. The four common gages were checked against the

master gage for comparable accuracies. The gages were checked

from 20. 5 psi to 29. 5 psi at approximately 0. 5 psi intervals. The

gage with the smallest average error (0. 5 psi at 24 psi) was chosen for

the tests. The individual errors of the other gages varied from to

3. psi, or up to 10 percent of the master-gage reading.

Three ordinary tire-tread depth gages were procured and

checked at various indications against a precision micrometer depth

gage. Again, the gage with the smallest average error (0. 002 inch

between 4 and 12 thirty- seconds of an inch--the average tread depths

normally encountered on automobile tires) was chosen for the tests.

6. Safety Precautions

The fifth wheel was modified by installing a red warning flag on

a double-pole support, mounted on heavy-duty springs on the frame,

between the wheel and the clamp. Two large amber-lens flashing

lights were installed on a frame supported by suction cups and secured

by adjustable straps and hold-down clips. A danger sign was also

mounted on this frame which was placed on the rear trunk lid of each

car tested to warn the drivers of automobiles approaching from the

rear of the possibility of frequent stops in traffic lanes. (See figure

1.)

7. The Testing of Automobile Odometers Using

the Fifth Wheel

7. 1. Test Courses

The courses selected for the odometer-testing program included

busy city streets (for slow speeds) and a highway (for high speeds).

This provided an opportunity to evaluate the accuracy of the odometers

under both types of driving conditions. The city course involved four

right and three left turns, numerous stop signs and traffic lights,

single-lane and dual-lane traffic conditions, and a maximum speed

limit of 35 mph. The highway course was over a section of an interstate highway having a posted speed limit of 60 mph.

Originally, the test runs were 5 miles each and were made in

the following order: city-northbound, highway-northbound, (turn-
around), highway- southbound, city- southbound. This sequence provided duplicate data for the city and the highway runs. After twelve

cars were tested using the 5 -mile test runs, special tests were conducted to determine if a shorter test run would provide equally reliable

information. These tests involved cars of two different makes and at

least three replicates for each car over course lengths of 1 mile, 2

miles, and 5 miles. Comparative analysis of the data indicated that

two 2 -mile runs would actually provide better information than a

single 5 -mile run, since the total test variability in each 2 -mile run

was not significantly different from that in each 5 -mile run. However, the total test error in a one -mile run was sufficiently large

(approximately 0. 6 percent) to rule out the use of this course length.

The test runs were then made in the following order: two

successive 2 -mile city-northbound runs, two 2 -mile highwaynorthbound runs, (turn around), two 2 -mile highway- southbound runs,

and two 2 -mile city- southbound runs. This course then provided four

city runs and four highway runs, each 2 miles in length. The replicates made possible the elimination of any single runs which yielded

obviously faulty data, without significantly reducing the reliability of

the remaining data.

7. 2. Test Vehicles

The vehicles used in the odometer tests were provided by

Washington, D. C. , car -rental agencies through arrangements made

by the District Department of Licenses and Inspections. They were

selected at random from the fleet of cars available on any particular

day. The cars tested were predominently popular size cars and compacts. Of the 48 cars tested, 32 fell into these two groups, 16 in each

group. Four large, high-priced cars, 4 American sports cars, and

5 other luxury-type cars were tested. Also included in the test group

were 3 station wagons. All vehicles tested were of domestic manufacture.

7.3. Test Procedures and Observations

The vehicles to be tested were picked up at the car-rental

agency in the midtown area and driven to the grounds of the National

Bureau of Standards. Here, the fifth wheel was attached to the rear

bumper, the counter connected and secured, and the warning sign and

light bar attached to the rear trunk lid. The "Odometer Test Report"

data sheet (see figure 3) was filled in with such pre -test information

as vehicle, owner, number, make, model, mileage, and license

number, and also with data on the rear tires, including the manu-
Date: Time: 9 ^: M\ Temperature: / C. >

(J

J

Owner: Vehicle No. : (£> 2

A

5*?

Make: fl Model: |

Motor: (/_

Type:

§*" Serial No. :

*-doorDrive: Ax.il'tt- Il<ns3\24£

Mileage: S^2 5"^ License No. : K~T> £, 3 ,^_

Manuf. : Type: 9

Ti

I Size:

Diameter:

i :5t> > |4

Diameter:

Pressure: L^^R.^l RTP £4 -ead Depth: L^J? 1*9*4 ntd

Course

No : .>£_- Length: J2.0 fa rt Jejs

Notes: Ncr-rwM ""hrKTTf C.,

Results

C C

qo.r

H

<?4fT

H

Start: S5T '1 8*. 5" (H5 94-1

Miles * 20 5.0 st.o 3.0

Fifth- Wheel -- - End |".94SL 1.940 1-94-1

1 .94*?

Start: a O o

Miles Uncorrected: i c)4a. iMc 1 941 I,W

C. F. -COOS' -o.oar -O.C06 -0,006

Miles Corrected: *#i Cj ;3^i Iflsa. 1.9*1 1.943

Error-Fifth- Wheel Miles: **M 54 L932- |94| l.w

Vehicle Miles: * 2.eoe S.ooc 2.000 2,000

Difference: o.ou D.c^ 0.05^ O.CsT

•^ 3. 4 % 4^5T •f3.o l% 4-2.1%

Figure 3. Odometer Test Report

7
facturer, type, and size of the tires. The tread depth, measured at

4 points along a profile cross section of the tread, and the air pressure

in each tire were then measured and recorded. Following this, the

air pressure in each rear tire was adjusted to the pressure recommended by the tire manufacturer.

In preparation for the start of the test, the vehicle was driven

slowly until either the 5 or 7 tenth -mile figure reached a point in its

travel where the straight top edge of the number was just reaching the

bottom edge of the odometer window frame. (Assuming a fixed position of the driver's line of sight, this position of the odometer tenthmile indication could be repeated very accurately at the end of the test run. ) At this precise position of the odometer indication, the vehicle

was stopped, the fifth wheel was placed in operating position, the

counter energized and zeroed, and the first test begun. As the end of

the first test run was approached, the vehicle was slowed down and

then brought to a stop when the driver had duplicated, to the best of his

ability, the original position of the tenth-mile indication. The counter

indication was observed and recorded and the counter reset before the

second test run was started.

At the end of the second northbound highway test, the technician

checked the rear tire air pressures since the high speed driving

usually caused a pressure buildup. If necessary, the tire pressure

was again adjusted to the recommended pressure since the accumulation of comparative data was based on standard test conditions. The

southbound test-course procedures were the same as the northbound

procedures.

7. 4. Special Tests

Special tests were conducted to determine the effects of certain

variables on odometer accuracy- -wet pavements, vehicle speed,

vehicle load, and vehicle tire pressure.

Wet Pavements --Whenever a test in progress had to be stopped because of rain showers, a new test was started on the wet roadway and,

later, the same car was retested to provide complete information for

dry pavements.

Vehicle Speed- -Special tests were conducted over the highway course

to determine the effect of vehicle speed on odometer accuracy. Two

separate makes of medium-priced cars were selected for these tests.

Two-mile runs were made at speeds of 30 mph and 60 mph.
Vehicle Load- -The same two cars used in the special speed tests were

used in the load tests. Each vehicle was tested over the regular test

course with the driver only, and again with the driver plus 400 pounds

of 50 -pound weights, 100 pounds in the front seat and 300 in the rear

seat.

Vehicle Tire Pressure --Special tests were conducted to determine the

effect of pressures in excess of those recommended by the tire manufacturer on the accuracy of the odometer indication. Comparative

tests v/ere made at 24 psi and 30 psi over the normal test course.

8. Test Results

8.1. Odometer Accuracy

The average error for all cars driven under city and highway

conditions was +3.21 percent. The average error for all city runs was

+3. 50 percent, with a range of from +0. 10 percent to +7. 25 percent.

The average error for all highway runs was +2. 92 percent, with a range of from -0. 50 to +6. 90 percent. Table 1 shows the average

errors for the types and makes of automobiles tested under both city

and highway driving conditions.

Table 1. Average Automobile Odometer Errors

(Percent of Overregistration)

Vehicle

Type

Vehicle

Manufacturer

Number

Vehicles

City

Error

Highway

Error

Average

Error

Popular 12

Average

8

8

(16)

4.47

3. 00

3. 73

3. 98

2. 50

3. 24

4. 23

2. 75

3. 49

Compact 12

3

4

Average

4

4

4

4

(16)

5. 42

3.85

0.46

3. 11

3.21

4. 88

3. 18

0. 08

2. 62

2. 69

5. 15

3. 51

0. 28

2.87

2. 95

Luxury 12

3

Average

3

3

7

(13)

4. 28

3. 10

3. 29

3. 47

3. 63

2. 28

2. 54

2. 73

3. 96

2. 69

2. 91

3. 10

Wagon 1 (3) 3. 95 3.27 3. 61

Averages

,

(48) 3. 50 2. 92 3. 21
The average difference (which was fairly consistent for all tests)

between the city test and the highway test was 0. 6 percent. The odometer indicated more for the city run, providing greater overregistration errors. The test results for all cars are found in Appendix L

grouped by types of cars and by manufacturers.

8. 2. Effect of Variables

The specific results of the tests conducted to determine the effect

of these variables on odometer accuracy are not important in themselves and are not presented since they apply only to the individual

cars used in these specific tests. The differences in results of tests

conducted under different conditions are important as they indicate the

relative changes in the odometer errors as caused by the changes in

the testing conditions.

Wet Pavements

-Only a limited number of tests were conducted to

determine the effect of wet pavements on the odometer accuracy.

These data, however, provided indications that the slippage of the rear

wheels on the wet pavement caused larger positive errors than the drypavement tests. The errors obtained in the wet pavement tests were

up to one and one -half times as great as those obtained in the dry pavement tests.

Vehicle Speed- -A number of highway tests were conducted to determine

the effect of speed on odometer accuracy. These test data indicated

that as the vehicle speed was increased from 30 mph to 60 mph the

odometer reading was decreased, on the average, by a factor of 0. 55

percent of the distance traveled. The increase in vehicle speed caused

an increase in the rolling radius of the tire, which in turn reduced the

odometer indication.

Vehicle Load- -The tests conducted with an additional load of 400 pounds

in the vehicle provided an increase in the odometer reading, on the

average, of 0. 46 percent of the distance traveled. The increase in

load caused a decrease in the rolling radius of the tire, which in turn

caused an overregistration effect in the odometer indication.

Vehicle Tire Pre ssure --The tests conducted to determine the effect of

inflating the tires to 30 psi, or 6 psi above the recommended pressure

provided a decrease in the odometer reading of 0. 75 percent of the

distance traveled.

10
8. 3. Precision of Test

The uncertainty of the indicated odometer error that could be

attributed to the variability of the fifth-wheel tests was not more than

±0. 2 7 percent.''" This test error was well within the 1 percent error

limit which is recommended in NBS Handbook 44, entitled "Specifications, Tolerances, and Regulations for Commercial Weighing and

Measuring Devices. " This limit is arrived at considering the maximum error in the recommended testing equipment of 25 percent of the

tolerance to be applied.

8. 4. Test Conclusions

The results of these tests clearly indicate that through the use

of the fifth-wheel device, odometer errors can be determined by a

single run with a total uncertainty of less than one percent, allowing

0. 54 percent for the possible effect of random variations and the remaining part of the allowance for possible systematic errors.

The results also indicated that the average odometer provided an

overregistration error of more than 3 percent under standard test

conditions. It was found that wet pavements and additional vehicle

loads tended to increase the odometer error, while increased vehicle

speed and increased tire pressures tended to decrease the odometer

error.

''"Successive runs did not yield identical results, as is illustrated

by the example given in figure 3. This variability is mainly due to

reading errors, but may also include the effects of such factors as

speed, temperature, and driver habits. A statistical analysis of the

variability led to a standard deviation of 0. 003 59 mile for a single

2-mile run (based on tests of popular cars involving 73 degrees of

freedom). Using three standard deviations as a limit of the effect of

random variation on the results, leads to an uncertainty value of ±0. 27

percent for the average of four runs. This value is related to the

precision of the measurement procedure and does not include any

allowance for systematic differences in the test procedure that would

be introduced if, for example, a tire pressure other than that specified

in the test were used.

11
9. The Testing of Truck Odometers

Using the Fifth Wheel

9. 1. Test Courses

The test course for the trucks tested was essentially the same as

the 2 -mile city and highway courses described for the automobiles.

Three trucks did not have tenth-mile odometer indications and were

driven over either at least two 5-mile courses or one 10-mile course.

9. 2. Test Vehicles

Ten of the trucks tested were obtained from two of the national

rental agencies in Washington, D. C. The other three trucks were

borrowed from the National Bureau of Standards motor pool. Six of

the trucks were panel trucks; four were rated at 1/2 ton, one at 3/4

ton, and one at 1 ton. Three of the trucks were pickups; one of these

was rated at 1/2 ton, and two at 3/4 ton. Two of the trucks were stepvans and two were 14-foot vans. Two trucks, a step -van and a pickup,

had snow tires on the rear wheels, but were tested to obtain data.

9.3. Test Procedures and Observations

The procedures followed and observations made during the

testing of truck odometers were essentially the same as those of the

automobile tests. The only differences occurred in the placing of the

fifth wheel in operating position prior to obtaining a precise odometer

indication at the start of the test. This was done to eliminate the need

for leaving the truck on the busy streets.

9. 4. Test Results

The average error for all trucks driven under both city and

highway conditions was -0. 4 percent. The average error for all city

runs was -0. 25 percent with a range of from +5. 2 percent to -5. 2

percent. The average error of all highway runs was -0. 55 percent

with a range of from +5. 2 percent to -5. percent. The average error

for the eleven trucks with regular tires (eliminating from the average

the two trucks with snow tires) was +0. 8 percent. The average error

for the city runs was +1. 2 percent and the average error for the highway runs was +0. 6 percent for these eleven trucks. The results of all

trucks tested are found in Appendix II.

12
9. 5. Effects of Variables

One truck, a 3/4 ton pickup, was selected to determine the effect

of the various variables on the resulting odometer accuracy. This

truck had an average odometer error of +0. 8 percent for the normal

city runs. Highway speeds of up to 50 mph did not significantly influence this error under any conditions. However, an increase in tire

pressure from 30 psi (recommended) to 60 psi caused a decrease in

the odometer reading of 0. 9 percent of the distance traveled. An

increase in load of 1550 pounds per rear tire (at 30 psi) caused an

increase in the odometer reading of 1. 4 percent of the distance

traveled. The effects of these variables caused changes in the rolling

radius of the tires, which in turn caused the change in odometer

accuracy.

9. 6. Precision of Tests

The limits of variability of the test results, were found to be

±0. 35 percent for trucks as compared to the ±0. 27 percent found in the

automobile test. This increased variability is mainly attributable to

the difficulty in precisely duplicating the odometer indications used in

the test. The difficulty in reading truck odometers was caused by the

parallax effects created by the greater distances between the instrument panels and the odometer figures in trucks as compared to those

found in automobiles.

10. Road Tests

Tests were conducted over measured courses one mile and two

miles in length with three different automobiles to determine the

effectiveness of the road test in determining odometer accuracy. The

measured courses were laid out with the fifth wheel on fairly straight

and level concrete highways. The beginning and end of each course

was prominently marked. Courses were laid out along both the northbound and the southbound lanes so that data could be obtained while

traveling in both directions.

10. 1. Test Procedures and Observations

The pre-test procedures and observations utilized in the fifthwheel tests were also followed in the road tests. Following this, the

vehicle to be tested was driven to the starting point and accurately

positioned by lining up a point in the right window with two points

placed in a line perpendicular to the roadway at the starting point. The

front wheels of the vehicle were then blocked with chocks, and the rear

13
wheels were raised from the roadway surface by jacking up the rear

end. The technician then started the motor and allowed the odometer

to advance until the tenth- mile digit reached a test starting point.

After accurately positioning the tenth-mile digit, the jack was

released and the chocks removed. The technician then drove the

vehicle over the course until either the 1.0- or 2. 0-mile indication was

obtained. At this point the vehicle was stopped, and a mark was made

on the pavement even with the point in the front right window which was

previously used, to determine the position of the vehicle at the starting

point.

The distance from this point to the end of the course was then

measured with a calibrated 100-foot steel tape. This distance, representing the error of the odometer was used in determining the variations resulting from the use of this type of test. The fifth wheel was

used in these tests as the standard mileage-measuring instrument and

data obtained through the use of the wheel was also recorded.

10. 2. Test Results

The results obtained using the Road Test in determining odometer errors are shown in Table 2. The maximum difference observed

between the fifth-wheel test and the road test for a one-mile course

was 5. feet, the average difference was only 1. 6 feet. The results

for the two-mile course indicated a maximum difference of 10. feet

with an average difference of only 4. 2 feet.

Table 2. Odometer Errors Observed in Road Tests

(Averages of Four Test Runs)

Car Course

Average

5th-Wheel

Error

Average

Measured

Error

Range of

Differences

Average

Difference

A

(miles)

12

(feet)

117. 5

229. 7

(feet)

115. 4

236. 3

(feet)

-1. 3 to +5. 1 -10. to -4. 2

(feet)

-2. 1 +6. 6

B 12

260.

493. 7

260.2

491.2

-1.2 to +2. 1 -6. to +1.+0.2

+2. 5

C 12

264.0

554. 4

263.8

556. 7

-1. 2 to +0. 7

+1. 9 to +2. 6

-0.2

+2. 3

14
10. 3. Test Conclusions

These results proved that an accurately measured course of

either one or two miles can provide very satisfactory evaluations of

odometer accuracies if precision and exacting procedures are employed during the testing operations.

The one-mile test courses provided an average difference of

1. 6 feet between the fifth -wheel tests and the road tests. Two-mile

test courses provided an average difference of 4. 2 feet between the two

types of test.

11. Simulated-Road Tests

Simulated-road tests were conducted using a commercial device

made specifically for odometer testing. This device consisted of two

pairs of accurately machined rollers, approximately 8 inches in

diameter, supported by heavy-duty bearings, mounted in a steel frame.

An electrical contactor was connected through a gear reduction unit to

one of the rear cylinders under the rear wheel of the vehicle being

tested. A ramp was provided to allow the vehicle to be positioned on

the rollers. A high-speed electrical counter was provided which

indicated distance traveled in tens, units, tenths, hundredths, and

thousandths of miles. The power required to actuate the circuit was

provided through a common 115-volt a. c. outlet. Specifications for

this type of odometer testing equipment are found in Appendix IV.

11. 1. Device Calibration

The simulated-road testing device was calibrated by computing

the distance traveled by the cylinder in an indicated mile and determining the correction factor. The distance traveled per indicated

mile was computed by determining the measured circumference of the

cylinder and multiplying it by the exact number of revolutions in an

indicated mile. The distance traveled by the surface of the cylinder

was 5293 feet for each 1. 000 mile indicated by the simulated- road

testing device counter. Thus, one mile would be equal to an indication

of 0. 997, or a correction factor of -0. 003 mile would have to be applied

to each mileage indication provided by the simulated-road testing

device.

ac

11.2. Tests Conducted

The simulated-road testing equipment was used to evaluate the

accuracy of a vehicle odometer under a number of conditions to deter15
mine their relative effects on the resulting accuracy. These conditions

were as follows:

1. Car inclined and car level.

2. 2 5 mph and 50 mph„

3. Driver only and driver plus 400-pound load.

4. 24 psi tire pressure and 30 psi tire pressure.

5. Reading precision- -operator differences.

A test distance of two miles was selected, on the basis of the determination made in the fifth-wheel tests for the optimum length of test.

Only one car was involved in these tests, as this was considered

sufficient, from a study of the method, to determine the effectiveness

of the simulated- road tests in duplicating the results of the actual road

tests.

11. 3. Test Procedures and Observations

After completion of the previously established pre-test procedures and observations, the vehicle under test was positioned with the

rear wheels on the cylinders of the testing device. The tire pressure

was checked and adjusted if necessary, and then the rear wheels

advanced under power until the odometer indication reached a starting

point. At this time the counter circuit was energized and the indicator

was zeroed. Two indicated odometer miles were then traveled, the

vehicle wheels stopped exactly at the same tenth mile indication that

was used in starting the test. The counter indication at this point was

then read and recorded.

11.4. Test Results

The average error of the odometer on the vehicle tested in level

position under the standard conditions of 25 mph, 24 psi tire pressure,

and with the driver only in the car was 0.075 mile in two miles or an

overregistration error of 3. 75 percent. The range encountered in the

twenty runs was from 3. 50 percent to 3. 95 percent.

The results of the tests conducted to determine the effect of the

position of the car (level versus inclined) on the simulated-road

testing device indicated an average difference of 0. 002 mile in the twomile run or 0. 1 percent. The tests conducted with car level yielded

higher counter reading than those conducted with the car inclined, thus

the inclined position caused a greater overregistration of the vehicle

odometer than the level position. The difference, however, in the

16
results obtained from the two positions was not statistically significant.

Thus, it was reasoned that tests could be conducted with cars positioned on the incline resulting from backing the rear wheels of the

vehicle up on the unit; the unit being located on the road surface, and

the front wheels of the vehicle under test remaining at road surface

level.

The results of the tests conducted to determine the effect of

speed on odometer accuracy indicated that at 25 mph the vehicle

odometer had a 0. 6 percent greater overregistration than at 50 mph.

The results of the tests conducted to determine the effect of an

additional 400 -pound load on the odometer error indicated that this

additional load reduced the rolling radius sufficiently to cause an overregistration error 0. 7 percent greater than the errors incurred in the

tests conducted with the driver only.

The simulated-road tests conducted to evaluate the effect of an

increased tire pressure, 6 psi above the normal 24 psi, showed that

the increased rolling radius of the overinflated tire provided a smaller

overregistration error than the error provided by the normally inflated tires.

The tests conducted to determine reading precision of various

people indicated that odometer indication could be repeated to within

0. 001 mile by an experienced operator. Differences of up to 0. 005

mile were obtained by inexperienced people who participated in these

particular tests.

11. 5. Test Conclusions

The tests involving the simulated- road testing equipment proved

that this equipment, when used in conjunction with the specific test

procedures developed for this testing and conducted by experienced

personnel, could very accurately and effectively provide an evaluation

of vehicle odometer accuracy. The accuracy of the simulated-road

tests was not significantly different from that of the fifth -wheel tests.

The results of tests conducted to determine the effects of the variables

were very similar to the results obtained in the fifth-wheel road tests.

12. Wheel Tests

Wheel tests were conducted in an effort to evaluate the effectiveness of this type of test in determining the accuracy of a vehicle

17
odometer. The vehicle that was used in these tests, obtained from the

GSA motor pool, was a popular-sized 4-door sedan.

12. 1. Test Procedures and Observations

The vehicle was positioned on straight and level section of roadway, and a chalk mark was placed on the side wall of the tire, perpendicular to the pavement, and another mark was placed on the pavement, perpendicular to the tire, as the starting line. The car was

then slowly driven on a straight path until the wheel had made exactly

ten revolutions, as determined by an observer walking along beside

the car. At the point where the line on the tire was again exactly

perpendicular to the roadway, a chalk mark was made on the pavement. The distance between this point and the starting point was

measured with a calibrated 100-foot steel tape. This distance was

used to calculate the distance traveled per wheel revolution, or the

effective tire circumference. This procedure was repeated three

times.

The vehicle was then positioned on a level section of pavement,

the front wheels were blocked with chocks, and the right rear wheel

was jacked up. A revolution counter, held by a clamp on a laboratory

stand, was then attached by means of a suction cup. The technician

started the motor and allowed the tenth-mile digit of the odometer to

reach a starting point. After setting the counter at zero, the odometer was allowed to advance exactly one mile, and the number of wheel

revolutions was noted. This entire procedure was repeated three

times.

12.2. Test Results

The results of the three determinations of the distance traveled

per wheel revolution were as follows:

(a) 67 ft 10 in. or 6. 783 feet per revolution.

(b) 68 ft 4 in. or 6. 833 feet per revolution.

(c) 68 ft 2 in. or 6. 817 feet per revolution.

The results of the determination of revolutions per indicated

odometer mile were as follows:

(a) 751. 8 revolutions per mile.

(b) 749. 4 revolutions per mile.

(c) 753. revolutions per mile.

18
If the average of the three determinations of feet per revolution

were used in computing the distance traveled for each of the three

odometer miles, a maximum difference of 24. 6 feet or 0. 47 percent

would result. If the extremes of each of the determinations were used

in computing the distance traveled, a maximum difference of 62 feet or

1. 17 percent would result. These figures indicate that the wheel test

is not an accurate method of evaluating odometer accuracy, since the

errors involved exceed the 1. percent limit normally imposed in

odometer testing programs.

12. 3. Test Finding

A second and third car were also selected for the wheel test,

but it was found that, due to a new device in the rear end which prevents differential slip, it was impossible to advance only one wheel at

a time. When both wheels were jacked up, one wheel rotated forward

while the other rotated backward, reducing the total forward revolutions per wheel.

12. 4. Test Conclusion

The results of the one possible test, as well as the findings in

two additional tests, indicated that the wheel test could not effectively

be used to determine the accuracy of vehicle odometers, since

differences in excess of 1. percent could result from variations of

the number of revolutions per mile.

13. Conclusions

The test results indicated the average automobile odometer

tested provided an overregistration error slightly greater than 3 percent under standard test conditions. It was found that wet pavements

and additional vehicle loads tended to increase the overregistration

error, while increased vehicle speeds and tire pressures tended to

decrease the overregistration error.

The results of the limited number of tests conducted to determine the error of truck odometers provided an average error of +0.8

percent. It was found that vehicle speed had little effect on the resulting error although tire pressure and vehicle load did significantly

effect the odometer error.

It was found that vehicle odometer accuracy can be evaluated

quite precisely by a number of methods. The fifth-wheel device, the

19
simulated -road testing device, and the measured road course were

successfully used in this investigation of odometer accuracy. The

wheel test was found to be inadequate for odometer testing.

The fifth-wheel tests and the simulated- road tests were found to

have the highest degree of repeatability and precision. The road test,

because of the dependence upon the driver to duplicate exactly the test

course with each car tested, had slightly lower precision than the

other two methods. However, any testing program involves the use of

specific test procedures, precise determinations, carefully maintained equipment, and accurate interpretation of data.

The author wishes to acknowledge the assistance received from

(1) J. M. Cameron, Division 11.03, for the statistical analysis and

interpretation of the data; (2) H. F. Wollin, Division 17.0, for conducting the simulated-road tests; (3) J. H. Griffith, Division 17.0, for

conducting the other tests; and (4) M. W. Jensen, Division 17. 0, for

his guidance and contributions.

20
Appendix I Summary of Automobile Odometer Accuracy Tests

(Using Fifth-Wheel Device)

Test Type City Highway Average

Number Vehicle Error--% Error--% Error--%

1 P-l 2. 60 2.22 2. 41

2 P-l 3.36 2.84 3. 10

3 P-l 2. 98 2.24 2. 61

4 P-l 5.32 4. 36 4. 84

5 P-l 6.24 5. 72 5. 98

6 P-l 5. 18 4.74 4. 96

7 P-l 6.52 6.24 6. 38

8 P-l 3. 55 3.52 3. 54

9 P-2 3. 16 2. 54 2. 85

10 P-2 3.20 2. 66 2. 93

11 P-2 3.48 2. 90 3. 19

12 P-2 2. 68 2. 14 2. 41

13 P-2 3. 54 2. 98 3. 26

14 P-2 4. 16 3. 68 3. 92

15 P-2 0.48 -0. 10 0. 19

16 P-2 3.30 3. 16 3.23

17 C-l 5.30 4.95 5. 12

18 C-l 7.25 6. 90 7. 08

19 C-l 5.00 4.20 4. 60

20 C-l 4. 15 3. 45 3.80

21 C-2 4.05 3. 60 3. 82

22 C-2 3.50 2.55 3. 02

23 C-2 4. 15 3. 55 3.85

24 C-2 3.70 3.00 3. 35

25 C-3 0.30 0.01 0. 15

26 C-3 0. 70 0.30 0. 50

27 C-3 0. 75 0. 50 0. 62

28 C-3 0. 10 -0.50 -0.20

21
Appendix I (Continued)

Summary of Automobile Odometer Accuracy Tests

(Using Fifth-Wheel Device)

Test Type City Highway Average

Number Vehicle Error--% Error- -% Error- -%

29 C-4 3.25 2. 60 2. 92

30 C-4 1.00 0. 50 0. 75

31 C-4 5.25 4. 75 5.00

32 C-4 2. 95 2. 65 2.80

33 L-l 2.35 1. 70 2.02

34 L-l 5.00 4. 30 4. 65

35 L-l 5. 50 4. 90 5.20

36 L-2 3.00 2.20 2. 60

37 L-2 3. 10 2. 30 2. 70

38 L-2 3.20 2. 35 2. 78

39 L-3 2. 40 1. 50 1. 95

40 L-3 2. 95 2. 15 2.55

41 L-3 3. 15 2. 55 2.85

42 L-3 3. 75 3. 25 3.50

43 L-3 2. 55 1. 35 1. 95

44 L-3 1. 70 0. 75 1.22

45 L-3 6. 50 6.20 6.35

46 W-l 4. 30 4. 00 4. 15

47 W-l 2. 15 1. 20 1. 68

48 W-l 5.40 4. 60 5.00

Average 3. 50 2. 92 3.21

Key to Type of Vehicles

P = Popular Size Cars

C = Compact Cars

L = Luxury and Sport Cars

W = Station Wagons

Numbers differentiate car manufacturers,

22
Appendix II Summary of Truck Odometer Accuracy Tests

(Using Fifth-Wheel Device)

Test Type City Highway Average

Number Vehicle Error--% Error--% Error--%

1 P-l -4.3 -4.3 -4.3

2 P-l -0.8 -0.9 -0.8

3 P-l 0.1

4 P-l 1.1 1.0 1.0

5 P-2 0.4 0.2

* P-2 2.6 2.7 2.6

Average -0. 15 -0. 25 -0. 20

7 U-l (ST) (-4.5) (-5.0) (-4.8)

8 U-2 (NTW) 1.6

9 U-2

Average

0.8

1.2

0.8 0.8

10 S-l (ST) (-5.2) (-5.0) (-5.1)

11 S-2 5.2 5. 2 5.2

12 V-l (NTW) 2.9 — — — — — _ 13 V-2 (NTW)

Average

3. 2

3.05

— — — — — —

Averages (w/o U-l & S-l) 1.2 0. 6 0.8

Key to Trucks

P = Panel Truck

U = Pickup Truck

S = Step Van

V = 14' Van

ST = Snow Tires

NTW = No Tenth Wheel

23
Appendix III PROPOSED

OWM SPECIFICATIONS

FOR

"FIFTH-WHEEL" TESTING EQUIPMENT

1. General . --This specification describes a precision distancemeasuring device to be used by weights and measures officials

for the testing of odometers and taximeters.

1.1. Material. --The material to be used in the construction of

this device shall be such as to provide strength, durability, corrosion resistance, and permanence.

1.2. Design. --The design of this device shall be such as to

provide permanence, accuracy, ease of use, and

maintenance -free operation.

1.3. Components. --The device shall include the wheel

assembly, frame, bumper mounting clamp, tension

springs, and a distance-indicating system.

2. Wheel Assembly. --The wheel assembly shall consist of a tire, a

rim, spokes, hubs, and bearings, and shall be mounted in a

suitable frame (see 3. ).

2. 1. Tire . --A 26-inch x 2. 125-inch bicycle-type tire shall be

used. It shall be carefully selected for good balance

and run-out characteristics.

2.2. Rim. --A heavy-duty bicycle-type rim shall be used. It shall be carefully balanced.

2.3. Spokes . --Thirty-six spokes of 105 gage shall be used.

2.4. Bearings. --Large-diameter, heavy-duty, double-row,

sealed ball bearings shall be used. They shall be

essentially frictionless.

24
3. Frame. --The frame shall be constructed of a very strong, fairly

lightweight material which shall provide a rigid support for the

wheel. It shall also provide for the installation and operation

of the tension springs, the bumper clamp, and the distance

indicating system.

4. Bumper Clamp. --The bumper clamp shall provide for the attachment of the frame to rear bumper of various vehicles. It shall

be of universal design or shall be supplied with various adapters so that it will be susceptible of being attached to the

majority of automobile bumpers in use today.

Tension Springs. --A matched pair of springs shall be included in

the design of the device and shall be attached to the frame in

such a manner as to provide a constant pressure of the tire on

smooth roads. The springs may also be used to hold the

device in a vertical position when not in use.

Distance -Indicating System. --A distance -indicating system shall

be provided which will accurately indicate distance in thousandths (0. 001) of a mile, up to 9. 999 miles, at speeds up to

55 miles per hour. It shall be provided with a 20-foot connecting cable to allow the indicator to be located near the driver's

wheel of the vehicle under test.

If the indicating device is electrical, it shall be powered by a

12 -volt source, and adapters shall be included which will

allow the use of the vehicle cigarette lighter socket and any

other 12-volt power source.

If the indicating device is mechanical, it shall be lubricated

for life and shall be provided with rotation arrows permanently

attached to each end of the cable. A dial indicator may be used

to indicate thousandths of a mile, but a digital indicator shall

be used for the hundredths, tenths, and unit miles.

Warning Device. - -A warning light (flashing light) or flag shall be

provided which will be securely mounted 4 feet above the

ground. If a flag is used, the bracket shall be mounted on

springs. Provision shall be made to allow the wheel to be

placed in a nearly vertical position for transport purposes.

25
Appendix IV

PROPOSED

OWM SPECIFICATIONS

FOR

SIMULATED-ROAD TESTING EQUIPMENT

1. General. --This specification describes a precision distancemeasuring device to be used in simulated-road tests by

weights and measures officials in the testing of odometers and

taximeters.

1.1. Material. --The material to be used in the construction

of this device shall be such as to provide strength,

durability, corrosion resistance, and permanence.

1.2. Design. --The design of this device shall be such as to

provide permanence, accuracy, ease of use, and

maintenance-free operation.

1.3. Components. --The device shall include a frame, at

least two revolving cylinders, and a distance

indicating system.

2. Frame . --The frame shall be designed to accommodate for test

purposes vehicles weighing up to 6, 000 pounds with wheel

bases of up to 132 inches (11 feet). It shall be designed and

fabricated to provide for either recessed, permanent installation in a floor or temporary installation on a paved surface.

If designed for the latter, it shall include approach ramps and

be composed of 3 -foot sections, each susceptible to quick

attachment, correct fitting, and easy handling. The frame

shall include appropriate wheel guides to prevent the vehicle

from sliding laterally.

3. Cylinders . --The cylinders shall be at least 34 inches wide and

approximately 8 inches in diameter, with solid end caps and

with solid steel shafting extending through the cylinders. The

shafts are to be supported by heavy-duty bearings designed to

accommodate the test loads with 20, 000 hours minimum life

expectancy.

26
The front cylinder shaft shall be connected to a positive mechanical braking device which will allow the vehicle to leave

the testing device. The rear cylinder shaft shall be precisely

machined to provide accurate distance indications through an

appropriate system.

4. Distance -Indicating System. --A distance-indicating system shall

be provided which will indicate distance in thousandths (0. 001)

of a mile, up to 9. 999 miles, at speeds up to 55 miles per

hour. It shall be provided with a 20-foot connecting cable to

allow the indicator to be located near the driver's wheel of the

vehicle under test.

If the indicating device is electrical, it shall be powered by

either a 115-volt or 12-volt source. If 12-volt power is used,

adapters shall be included which will allow the use of the

vehicle cigarette lighter socket as well as any other 12-volt

source of power.

If the indicating device is mechanical, it shall be lubricated

for life and shall be provided with rotation arrows permanently attached to each end of the cable. A dial indicator may

be used to indicate thousandths of a mile, but a digital indicator shall be used for the hundredths, tenths, and unit miles.

27

* U.S. GOVERNMENT PRINTING OFFICE . 1963 0—695-931

U. S. DEPARTMENT OF COMMERCE

Luther H. Hodges, Secretary

NATIONAL BUREAU OF STANDARDS

A."V. Astin, Director THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its major laboratories in Washington, D.C.and

Boulder, Colorado, is suggested in the following listing of the divisions and sections engaged in technical work.

In general, each section carries out specialized research, development, and engineeringin the field indicated by

its title. A brief description of the activities, and of the resultant publications, appears on the inside of the

front cover. WASHINGTON, D. C.

Electricity. Resistance and Reactance. Electrochemistry. Electrical Instruments. Magnetic Measurements.

Dielectrics. High Voltage. Absolute Electrical Measurements.

Metrology. Photometry and Colorimetry. Refractometry. Photographic Research. Length. Engineering Metrology. Mass and Volume.

Heat. Temperature Physics. Heat Measurements. Cryogenic Physics. Equation of State. Statistical Physics.

Radiation Physics. X-ray. Radioactivity. Radiation Theory. High Energy Radiation. Radiological Equipment.

Nucleonic Instrumentation. Neutron Physics.

Analytical and Inorganic Chemistry. Pure Substances. Spectrochemistry. Solution Chemistry. Standard Refer- ence Materials. Applied Analytical Research. Crystal Chemistry. Mechanics. Sound. Pressure and Vacuum. Fluid Mechanics. Engineering Mechanics. Rheology. Combustion

Controls. Polymers. Macromolecules: Synthesis and Structure. Polymer Chemistry. Polymer Physics. Polymer Characterization. Polymer Evaluation and Testing. Applied Polymer Standards and Research. Dental Research.

Metallurgy. Engineering Metallurgy. Metal Reactions. Metal Physics. Electrolysis and Metal Deposition.

Inorganic Solids. Engineering Ceramics. Glass. Solid State Chemistry. Crystal Growth. Physical Properties.

Crystallography.

Building Research. Structural Engineering. Fire Research. Mechanical Systems. Organic Building Materials. Codes and Safety Standards. Heat Transfer. Inorganic Building Materials. Metallic Building Materials. Applied Mathematics. Numerical Analysis. Computation. Statistical Engineering. Mathematical Physics. Operations Research. Data Processing Systems. Components and Techniques. Computer Technology. Measurements Automation. Engineering Applications. Systems Analysis.

Atomic Physics. Spectroscopy. Infrared Spectroscopy. Far Ultraviolet Physics. Solid State Physics. Electron Physics. Atomic Physics. Plasma Spectroscopy.

Instrumentation. Engineering Electronics. Electron Devices. Electronic Instrumentation. Mechanical Instru- ments. Basic Instrumentation. Physical Chemistry. Thermochemistry. Surface Chemistry. Organic Chemistry. Molecular Spectroscopy. Ele- mentary Processes. Mass Spectrometry. Photochemistry and Radiation Chemistry.

Office of Weights and Measures. BOULDER, COLO.

CRYOGENIC ENGINEERING LABORATORY

Cryogenic Processes. Cryogenic Properties of Solids. Cryogenic Technical Services. Properties of Cryogenic

Fluids. CENTRAL RADIO PROPAGATION LABORATORY

Ionosphere Research and Propagation. Low Frequency and Very Low Frequency Research. Ionosphere Research. Prediction Services. Sun-Earth Relationships. Field Engineering. Radio Warning Services. Vertical Soundings Research. o~ Troposphere and Space Telecommunications. Data Reduction Instrumentation. Radio Noise. Tropospheric Measurements. Tropospheric Analysis. Spectrum Utilization Research. Radio-Meteorology. Lower Atmosphere

Physics.

Radio Systems. Applied Electromagnetic Theory. High Frequency and Very High Frequency Research. Fre- quency Utilization. Modulation Research. Antenna Research. Radiodetermination. Upper Atmosphere and Space Physics. Upper Atmosphere and Plasma Physics. High Latitude Ionosphere

Physics. Ionosphere and Exosphere Scatter. Airglow and Aurora. Ionospheric Radio Astronomy.

RADIO STANDARDS LABORATORY

Radio Standards Physics. Frequency and Time Disseminations. Radio and Microwave Materials. Atomic Fre- quency and Time-Interval Standards. Radio Plasma. Microwave Physics.

Radio Standards Engineering. High Frequency Electrical Standards. High Frequency Calibration Services. High

Frequency Impedance Standards. Microwave Calibration Services. Microwave Circuit Standards. Low Frequency

Calibration Services.

Joint Institute for Laboratory Astrophysics - NBS Group (Univ. of Colo.).
]

NBS