ASTM E4:20 pdf download

ASTM E4:20 pdf download.Standard Practices for Force Verification of Testing Machines.
4.2 The procedures in Practices E4 may be used by those using, manufacturing, and providing calibration service for testing machines and related instrumentation.
5. Force-Measuring Instruments
5.1 When verifying testing machines, use force-measuring instruments only over their Class A force ranges as determined by Practice E74.
6. Advantages and Limitations of Methods
6.1 Verification 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 he actuated by a downward force,
6.2 Verification by Equal-Ann 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 only to certain types of hardness testing machines in which the force is applied through an internal lever system.
6.3 Verification by Force-measuring Instru,,,ents—The third method of verification of testing machines involves measurement of the elastic strain or deflection under force of a ring, ioop, tension or compression bar, or other force-measuring instrument. The force-measuring instrument 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 .4 and 1.6) in place and operating as in actual use.
7. 1 . I If this is not technically possible, refer to Annex A I, 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 A 1
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 Al.
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 routinelyinstalled and uninstalled in the testing machine. For suchdevices，interchangeability shall be established during theoriginal verification and shall be reestablished after an adjust-ment is performed. This is accomplished by performing anormal verification with the device in place as during normaluse. It is advisable that orientation be kept consistent, such asby noting the direction of the cable connector so that whenreinstalling the device, the orientation will be repeated. Re-move and reinstall the device between the two verification runsto demonstrate interchangeability. Repeat the procedure foreach interchangeable force measuring device used in the testing machine.