Force measuring devices may require calibration in tension and/or compression. Calibration may be by either: direct comparison with certified standard weights or direct comparison with devices meeting the requirements of ASTM E 74.
The calibration procedure normally consists of 20 to 30 separately applications of known loads.
Force and load measuring devices include proving rings (dynamometers), electronic load cells, and hydraulic load indicators. Calibrate proving rings, electronic load cells, testing machines, and other devices annually.
Unless specified otherwise, the final calibration accuracy must be within plus or minus one percent.The values given in parentheses (if provided) are not standard and may not be exact mathematical conversions. Use each system of units separately. Combining values from the two systems may result in non conformance with the standard.
Proving rings are often used to calibrate the amount of force used within various force-testing devices. Once the calibration is set, other materials are placed in the devices, and it is possible to see if they can withstand the same force that was being applied to the proving ring.
Proving rings are calibrated in accordance with procedures established by the American Society for Testing and Materials in a standard designated as ASTM E 4 by direct comparison with devices meeting the requirements of ASTM E 74
The repeatability of both analog and digital models of Proving Rings is within 0.2% of the indicated load and the accuracy is +/- 1% of the indicated load over the upper 80% of the working range at the calibration loads.