Temperature measuring apparatus

Abstract

A measuring apparatus comprises: a first series circuit having first and second resistors connected between a power source terminal and ground; a second series circuit having a thermistor and a third resistor connected between the power source and ground; a first variable frequency oscillator for generating a pulse signal with the frequency corresponding to the current derived from the junction between the first and second resistors of the first series circuit; a second variable frequency oscillator for generating a pulse signal with the frequency corresponding to the current derived from the junction between the thermistor and the third resistor; a first counter which counts the pulse signal from the second variable frequency oscillator to produce a high level signal till it counts a given number of pulses; and AND gate connected to the output terminal of the first variable frequency oscillator and the first counter, a second counter for counting the pulse fed from the first variable frequency oscillator via the AND gate; and a display circuit for displaying the contents of the counter. The first and second variable oscillating circuits each have an odd number of inverters which are cascade-connected and each formed of an integrated injection logic circuit with a power receiving terminal connected to the first or second series circuit, the output terminal of the last stage inverter being connected to the input terminal of the first stage inverter.