The NAMAS approach to instrument specifications

Instrument specifications provide an essential guide to users about the performance that can be expected from electrical test equipment and measurement standards. This paper examines some of the aspects of instrument specifications and identifies the important areas where specifications have to be proved (or otherwise) by traceable measurements with appropriate uncertainties. NAMAS requirements for traceability and calibration are stringent but not unreasonable when seen from a scientific viewpoint. In many cases the secondary characteristics of an instrument, such as input resistance or temperature coefficient, can be determined in a practical manner without too much difficulty. In other cases the manufacturer´s specification can be used, where it appears reasonable, with verification of the performance of the equipment being established by internal comparisons or measurement audits