Supervisory device for wrong operation of varying quantity measuring

Abstract

A supervisory device of a varying quantity measuring apparatus including a main scale and an index scale which are moved relative to each other in accordance with a physical varying quantity, a main power supply circuit which outputs a predetermined DC stabilized voltage by operating a power switch, and an encoder which is driven by the voltage output from the main power supply circuit and converts the relative movement of said both scales into electric signals to be displayed. This device further includes an under voltage detecting circuit for supplying an under voltage detecting signal when the output voltage from said main power supply circuit falls below a standard voltage which is preestablished as the necessary voltage for normal operation of the encoder, and an error message output circuit for outputting an error message when the power switch of the main power supply circuit is operated as well as when an under voltage detecting signal is inputted, and is characterized in that errors in operation of the encoder caused by insufficient output voltage from the main power supply circuit can be displayed as an alarm by means of the error message from the error message output circuit.