Transforming the conversion characteristic of a measuring system used for technical control

Abstract

As it is known, the real conversion characteristic of a measuring system is different than the nominal characteristic, e.g. due to lower sensitivity and (or) the presence of nonlinearity. In measurement control, particularly in the areas of the limiting values of tolerance interval, this can increase the effect of random variables, and consequently, this can increase a probability of erroneous decisions. A difference between the real and nominal conversion characteristic of a measuring system is corrected using the calibration procedure. But the real conversion characteristic remains unchanged. Therefore, during calibration it is necessary to transform a conversion characteristic and move it towards the nominal one considering the limiting values. The transformation of characteristic may proceed in several cycles, each one can consist of two phases-multiplicative and additive. In case of the multiplicative transformation, the cycle starts with the multiplicative phase (a change in sensitivity of the conversion characteristic). In this case, the probability of erroneous decisions at both stages, the multiplicative and additive, remains unchanged. In case of the additive transformation in the first (additive) phase of the cycle, there is a parallel displacement of the real conversion characteristic. In this case, in the second (multiplicative) stage, the probability of decision will be b times less than in additive stage cycle. For selecting the type of transformation and the number of cycles it is necessary, first of all, to inspect the relationship between components of errors of conversion measuring system and the length of the tolerance interval which is proportional to b. The relationships, which allow estimating the probability of erroneous decisions (both within a cycle and in the transition to next cycle of transformation) are obtained.