Study of reading errors when calibrating analog ohmmeters

The features of calibration of analog ohmmeters are considered. Two measurement schemes for calibration were studied: using a multivalued standard measure, which makes it possible to set the ohmmeter readings to the calibrated scale mark, and by a direct measurement of the resistance value of a standard single-valued measure using a calibrated ohmmeter. It is shown that in the first case, the reading error includes two components: the error due to the phenomenon of parallax and the error in aligning the ohmmeter needle with the calibrated scale mark. In the second case, instead of the last component, it is necessary to take into account the interpolation error. Expressions for the uncertainty evaluation of corrections for all components of the reading error for linear and nonlinear ohmmeter scales are given. Formulas have been obtained that make it possible to calculate the measured resistance value in the event that the ohmmeter needle falls between the marks of a nonlinear scale.