【国外标准】 Standard Practices for Force Calibration and Verification of Testing Machines

5.1 Testing machines that apply and indicate force are used in many industries, in many ways. They might be used in a research laboratory to measure material properties, or in a production line to qualify a product for shipment. No matter what the end use of the testing machine may be, it is necessary for users to know that the amount of force applied and indicated is traceable to the International System of Units (SI) through a National Metrology Institute (NMI). The procedures in Practices E4 may be used to calibrate these testing machines so that the measured forces are traceable to the SI. A key element of traceability to the SI is that the force measurement standards used in the calibration have known force characteristics, and have been calibrated in accordance with Practice E74.5.2 The procedures in Practices E4 may be used by those using, manufacturing, and providing calibration service for testing machines and related instrumentation.1.1 These practices cover procedures for the force calibration and verification, by means of force measurement standards, of tension or compression, or both, static or quasi-static testing machines (which may, or may not, have force-indicators). These practices are not intended to be complete purchase specifications for testing machines.1.2 Testing machines may be verified by one of the three following methods or combination thereof. Each of the methods require a specific measurement uncertainty, displaying metrological traceability to The International System of Units (SI).1.2.1 Use of standard weights,1.2.2 Use of equal-arm balances and standard weights, or1.2.3 Use of elastic force measurement standards.1.3 The procedures of 1.2.1–1.2.3 apply to the calibration and verification of the force-measuring systems associated with the testing machine, including the force indicators such as a scale, dial, marked or unmarked recorder chart, digital display, etc. In all cases the buyer/owner/user must designate the force-measuring system(s) to be verified and included in the certificate and report of calibration and verification.1.4 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.1.4.1 Other non-SI force units may be used with this standard such as the kilogram-force (kgf) which is often used with hardness testing machines1.5 Forces indicated on displays/printouts of testing machine data systems—be they instantaneous, delayed, stored, or retransmitted—which are verified with provisions of 1.2.1, 1.2.2, or 1.2.3, and are within the specifications stated in Section 15, comply with Practices E4.1.6 The requirements of these practices limit the major components of measurement uncertainty when calibrating testing machines. These Standard Practices do not require the allowable force measurement error to be reduced by the amount of the measurement uncertainty encountered during a calibration. As a result, a testing machine verified using these practices may produce a deviation from the true force greater than ±1.0 % when the force measurement error is combined with the measurement uncertainty.1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.