ASTM E4-99 pdf free download.Standard Practices for Force Verification of Testing Machines.
14. Temperature Equalization
14.1 When using an elastic calibration device to verify the readings of a testing machine, place the device near to. or preferably in, the testing machine a sufficient length of time before the test to assure that the response of device is stable.
14.2 During the verification, measure the temperature of the elastic device within ±2°F or ± 1°C by placing a calibrated thermometer as close to the device as possible.
14.3 Elastic calibration devices not having an inherent temperature-compensating feature must be corrected mathematically for the difference between ambient temperature and the temperature to which its calibration is referenced. Temperature-correction coefficients should be furnished (if applicable) by the manufacturer of the calibration device. Refer to Practice E 74 for further information.
15. Procedure
15.1 Place the elastic device in the testing machine so that its center line coincides with the center line of the heads of the testing machine. Record the Practice E 74 Class A verification value which establishes the lowest limit, or force level. allowable for the calibration device’s loading range (see Practice E 74). Each elastic calibration device is to be used only within its Class A force range and identified with the verification readings for which it is used.
15.2 To ensure a stable zero, flex the elastic device from no force to the maximum force at which the device will be used. Repeat as necessary, allowing sufficient time for stability.
15.3 There are two methods for using elastic calibration devices:
1 5.3. 1 Follow-the-Force Method—The force on the elastic calibration device is followed until the force reaches a nominal graduation on the force-readout scale of the testing machine. Record the force on the elastic calibration device.
15.3.2 Set-the-Force Method—The nominal force is preset on the elastic calibration device, and the testing machine force readout is read when the nominal force on the elastic calibration device is achieved.
15.4 After selecting suitable test force increments, obtain zero readings for both machine and elastic device, and apply forces slowly and smoothly during all verification measurements.
1 5.5 The calibration procedure must ensure that use of the maximum force indicator, recorder, or other accessory force devices does not cause testing machine errors to exceed the acceptable tolerances of 18.1.
15.6 Record the indicated force of the testing machine and the applied force from the elastic calibration device (temperature corrected as necessary). as well as the error and percentage of error calculated from the readings.ASTM E4 pdf download.