Electronic temperature measuring apparatus

Claim 1

Apparatus for producing a direct readout of temperature in degrees on a linear scale of a voltmeter from the change of resistance of a single temperature variable resistor comprising in combination, a temperature responsive circuit coupled between a pair of temperature measurement output terminals to develop a voltage thereat changing in a substantially linear relationship corresponding in degrees of temperature to said linear scale said circuit including said temperature variable resistor and a reference resistor of fixed resistance, both being conductively connected together at a common intermediate access terminal, said pair of temperature measurement output terminals conductively connected to the respective opposite ends of said two resistors, means developing a voltage at said terminals varying in response to temperature as a function of resistance change in said temperature variable resistor consisting of a pair of current sources each having a like pole conductively coupled respectively to said two output terminals to pass current through the respective two said resistors to said intermediate terminal to establish at a null temperature setting of 0* a cancellation of voltage drops across said two resistors as measured at said pair of output terminals, a voltmeter circuit incorporating said linear scale and responding to the voltage produced at said pair of output terminals thereby registering by changes of voltage an indication on said scale of the degrees of temperature at said variable resistor, and a potentiometer connecting each said current source together with the variable arm conductively coupled to said common intermediate access terminal for balancing current flows from the respective current sources at 0* to produce a null reading on said voltmeter scale.