ASTM E4-20 pdf free download.Standard Practices for Force Verification of Testing Machines.
10.3.3 If the highest decade is not a complete decade, choose verification forces at the possible ratios and include the upper limit of the verified force range. If the difference between two adjacent verification forces is greater than one- third of the upper limit, add an additional verification force.
Note 5—Example: A testing machine has a full-scale range of 5000 N and the resolution of the force indicator is 0.0472 N. The lowest possible verified force is 9.44 N (0.0472 x 200). Instead of decades starting at 9.44. 94.4 and 944 N. three decades. starting at 10, 100. and 1000 N arc selected to cover the verified range of forces. Suitable verification forces are 10. 20, 40. 70. 100, 200, 400, 700, 1000. 2000. 3000, 4000, 5,000. Note that the uppermost decade is not a complete decade and is terminated with the upper limit of the verified force range. The 3000 N reading was added because the difference between 2000 and 4000 was greater than one-third of 5000. If the alternative distribution of forces is used, the verification torces selected would be 10, 25, 50, 75, 100. 250. 500. 750, l000, 25(N), 3750, 5000.
10.4 All selected verification forces shall he applied twice during the verification procedure. Applied forces on the second run are to be approximately the same as those on the first run.
10.5 Approximately 30 s after removing the maximum force in a range, record the return to zero indicator reading. This reading shall be 0.0 ± either the resolution, 0. 1 % of the maximum force just applied, or I % of the lowest verified force in the range, whichever is greater.
11. Eccentricity of Force
11.1 For the purpose of determining the verified force range of a testing machine, apply all calibration forces so that the resultant force is as nearly along the axis of a testing machine as is possible.
Note 6—The efiect of eccentric force on the measurement accuracy of a testing machine may be determined by veriticaüon readings taken with force measurement standards placed so that the resultant ftrce is applied at definite distances from the axis of (he machine, and the verified force range determined for a series of eccentricities.
12. Methods of Verification
1 2. 1 Method A, Verification by Standard Weights:
1 2. 1 . I Procedure:
12.1.1.1 Place standard metal weights of suitable design, finish, and adjustment on the weighing platform of the testing machine or on trays or other supports suspended from the force measuring mechanism in place of the specimen. Use weights certified within five years to be accurate within 0.1 %. Apply the weights in ascending increments. If data is to be taken in both ascending and descending directions, remove the weights in reverse order. Record the forces, corrected for gravity and air buoyancy in accordance with Section 8.
Note7—The method of verification by direct application of standard weights can be used only on vertical testing machines in which the force on the weighing table, hydraulic support, or other weighing device is downward.
1 2.2 Method B. Verification Of Hardness Testing Machines by Ec,ual-Arin Balance and Standard Weights.ASTM E4 pdf download.