[Code of Federal Regulations]

[Title 40, Volume 31]

[Revised as of July 1, 2006]

From the U.S. Government Printing Office via GPO Access

[CITE: 40CFR1065.310]



[Page 719-720]

 

                   TITLE 40--PROTECTION OF ENVIRONMENT

 

         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)

 

PART 1065_ENGINE-TESTING PROCEDURES--Table of Contents

 

                Subpart D_Calibrations and Verifications

 

Sec.  1065.310  Torque calibration.



    (a) Scope and frequency. Calibrate all torque-measurement systems 

including dynamometer torque measurement transducers and systems upon 

initial installation and after major maintenance. Use good engineering 

judgment to repeat the calibration. Follow the torque transducer 

manufacturer's instructions for linearizing your torque sensor's output. 

We recommend that you calibrate the torque-measurement system with a 

reference force and a lever arm.

    (b) Recommended procedure. (1) Reference force quantification. Use 

either a set of dead-weights or a reference meter such as strain gage or 

a proving ring to quantify the reference force, NIST-traceable within 

0.5% uncertainty.

    (2) Lever-arm length quantification. Quantify the lever arm length, 

NIST-traceable within 0.5% uncertainty. The lever 

arm's length must be measured from the centerline of the dynamometer to 

the point at which the reference force is measured. The lever arm must 

be perpendicular to gravity (i.e., horizontal), and it must be 

perpendicular to the dynamometer's rotational axis. Balance the lever 

arm's torque or quantify its net hanging torque, NIST-traceable within 

1% uncertainty, and account for it as part of the 

reference torque.

    (c) Dead-weight calibration. This technique applies a known force by 

hanging known weights at a known distance along a lever arm. Make sure 

the weights' lever arm is perpendicular to gravity (i.e., horizontal) 

and perpendicular to the dynamometer's rotational axis. Apply at least 

six calibration-weight combinations for each applicable torque-measuring 

range, spacing the weight quantities about equally over the range. 

Oscillate or rotate the dynamometer during calibration to reduce 

frictional static hysteresis. Determine each weight's force by 

multiplying its NIST-traceable mass by the local acceleration of Earth's 

gravity (using this equation: force = mass [middot] acceleration). The 

local acceleration of gravity, ag, at your latitude, longitude, and 

elevation may be determined by entering position and elevation data into 

the U.S. National Oceanographic and Atmospheric Administration's surface 

gravity prediction Web site at http://www.ngs.noaa.gov/cgi-bin/grav--

pdx.prl. If this Web site is unavailable, you may use the equation in 

Sec.  1065.630, which returns the local acceleration of gravity based on 

a given latitude. In this case, calculate the reference torque as the 

weights' reference force multiplied by the lever arm reference length 

(using this equation: torque = force [middot] lever arm length).



[[Page 720]]



    (d) Strain gage or proving ring calibration. This technique applies 

force either by hanging weights on a lever arm (these weights and their 

lever arm length are not used) or by operating the dynamometer at 

different torques. Apply at least six force combinations for each 

applicable torque-measuring range, spacing the force quantities about 

equally over the range. Oscillate or rotate the dynamometer during 

calibration to reduce frictional static hysteresis. In this case, the 

reference torque is determined by multiplying the reference meter force 

output by its effective lever-arm length, which you measure from the 

point where the force measurement is made to the dynamometer's 

rotational axis. Make sure you measure this length perpendicular to 

gravity (i.e., horizontal) and perpendicular to the dynamometer's 

rotational axis.