ASTM E4-14 pdf free download.Standard Practices for Force Verification of Testing Machines.
5. Calibration Devices
5.1 When verifying testing machines, use calibration devices only over their Class A force ranges as determined by Practice E74.
6. Advantages and Limitations of Methods
6. 1 Verijicarion by Standard Weights—VerifIcation by the direct application of standard weights to the weighing mechanism of the testing machine, where practicable. is the most accurate method. Its limitations are: (1) the small range of forces that can be verified, (2) the nonportability of any large amount of standards weights, and (3) its nonapplicability to horizontal testing machines or vertical testing machines having weighing mechanisms that are not designed to be actuated by a downward force.
6.2 Verification by Equal-Arm Balance and Standard Weights—The second method of verification of testing machines involves measurement of the force by means of an equal-arm balance and standard weights. This method is limited to a still smaller range of forces than the foregoing method, and is generally applicable oniy to certain types of hardness testing machines in which the force is applied through an internal lever system.
6.3 Verijication by Elastic calibration Devices—The third method of verification of testing machines involves measurement of the elastic strain or deflection under force of a ring, loop, tension or compression bar, or other elastic device. The elastic calibration device is free from the limitations referred to in 6.1 and 6.2.
7. System Verification
7.1 A testing machine shall be verified as a system with the force sensing and indicating devices (see 1.2 and 1.4) in place and operating as in actual use.
7.1.1 If this is not technically possible. refer to Annex Al, Verifying the Force Measuring System out of the Test Machine. Out of the test machine verifications shall be in accordance with the main body of Practices E4 and its Annex A1.
7.2 System verification is invalid if the devices are removed and checked independently of the testing machine unless verification is performed according to Annex A1.
7.3 Many testing machines utilize more than one force measuring device in order to obtain more accurate force indication at lower applied forces. These devices are routinely installed and uninstalled in the testing machine. For such devices, interchangeability shall be established during the original verification and shall be reestablished after an adjustment is performed. This is accomplished by performing a normal verification with the device in place as during normal use. It is advisable that orientation be kept consistent, such as by noting the direction of the cable connector so that when reinstalling the device, the orientation will be repeated. Remove and reinstall the device between the two verification runs to demonstrate interchangeability. Repeat the procedure for each interchangeable force measuring device used in the testing machine.ASTM E4 pdf download.