Analysis and Comparison of Two Check Methods on a Tachometer Device

Abstract

Intermediate Check is an internal quality assurance process in calibration laboratories, conducted between the annual calibration intervals. The definition of an intermediate check is the process of confirming the test/calibration results and ensuring the validity of the calibrator instrument’s results, not the medical device itself. Among the calibrator instruments, one of them is the tachometer, which must undergo both calibration and intermediate checks. The intermediate check measurements are conducted on a regular schedule depending on the calibrator instrument and the testing/calibration institution. For the tachometer studied by the author, measurements were taken at three points: 1000 rpm, 3000 rpm, and 4000 rpm, in accordance with SNI ISO/IEC 17025:2017. In this study, the author compares and analyzes two tachometer check methods to determine which yields better accuracy. The two methods are: the intermediate check of the UUT (Unit Under Test) tachometer against a reference tachometer, and the UUT tachometer against a centrifuge, with results processed using control charts. At the 1000 rpm point, the first method showed an average of 999.47 rpm with a standard deviation of 0.06; at 3000 rpm, the average was 2999.48 rpm with a standard deviation of 0.05; and at 4000 rpm, the average was 3999.46 rpm with a standard deviation of 0.06.
The analysis showed that while the average values of both methods were nearly the same, the standard deviation was smaller in the method using the UUT tachometer with a reference tachometer. Based on the conclusions of this study, there is a measurable difference between the two methods, and the author recommends using the method involving the UUT tachometer and the reference tachometer.