[Code of Federal Regulations]
[Title 40, Volume 31]
[Revised as of July 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR1065.310]

[Page 720-721]
 
                   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 721]]

    (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.