Temperature measuring circuit

Claim 2

A temperature measurement circuit for providing an output signal varying linearly in response to temperature variations over a temperature range between temperatures T 1 and T 2 , the circuit comprising: a voltage source having a pair of output terminals and effective to supply a voltage V; a transistor having base, emitter and collector electrodes; a thermistor coupled between the collector electrode and one terminal of the voltage source, the thermistor having a resistance R t varying exponentially as a function of the temperature sensed by the thermistor; a resistor having a resistance R x coupled between the emitter electrode and the other one of the terminals of the voltage source, the quantity V ((k + R.sub.x)/( k + R.sub.x + R.sub.t)) being substantially linear as a function of temperatures sensed by the thermistor between the temperatures T 1 and a temperature T 3 intermediate the temperatures T 1 and T 2 and being nonlinear as a function of temperatures sensed by the thermistor between the temperatures T 3 and T 2 , where k is a constant equal to the voltage between the collector and emitter electrodes divided by the collector electrode current when the transistor is operated in its linear region; and bias means effective to bias the base electrode of the transistor so that the transistor is operated in its linear region for values of R t between the temperatures T 1 and T 3 and is operated between its linear and saturated regions for values of R t between the temperatures T 3 and T 2 , whereby the magnitude of the voltage at the collector electrode varies substantially linearly as a function of temperature between the temperatures T 1 and T 2 .

Claim 3

A temperature measurement circuit for providing an output signal varying linearly in response to temperature variations over a temperature range between temperatures T 1 and T 2 , the circuit comprising: a voltage source effective to supply a voltage V; an NPN transistor having base, emitter and collector electrodes; a negative temperature coefficient thermistor coupled between the collector electrode and the positive side of the voltage source, the thermistor having a resistance R t varying exponentially as a function of the temperature sensed by the thermistor; a resistor having a resistance R x coupled between the emitter electrode and the negative side of the voltage source, the quantity V ((k + R.sub.x )/(k + R.sub.x + R.sub.t)) being substantially linear as a function of temperatures sensed by the thermistor between the temperatures T 1 and a temperature T 3 intermediate the temperatures T 1 and T 2 and being nonlinear as a function of temperatures sensed by the thermistor between the temperatures T 3 and T 2 , where k is a constant equal to the voltage between the collector and emitter electrodes divided by the collector electrode current when the transistor is operated in its linear region; a voltage divider coupled across the voltage source and effective to generate a bias voltage; and means effective to couple the bias voltage to the base electrode of the transistor, the bias voltage having a value so as to bias the base electrode of the transistor so that the transistor is operated in its linear region for values of R t between the temperatures T 1 and T 3 and is operated between its linear and saturated regions for values of R t between the temperatures T 3 and T 2 , whereby the magnitude of the voltage at the collector electrode varies substantially linearly as a function of temperature between the temperatures T 1 and T 2 .

Claim 4

A temperature measurement circuit for providing an output signal varying linearly in response to temperature variations over a temperature range between temperatures T 1 and T 2 , the circuit comprising: a voltage source effective to supply a voltage V; an NPN transistor having base, emitter and collector electrodes; a negative temperature coefficient thermistor coupled between the collector electrode and the positive side of the voltage source, the thermistor having a resistance R t varying exponentially as a function of the temperature sensed by the thermistor; a resistor having a resistance R x coupled between the emitter electrode and the negative side of the voltage source, the quantity V ((k + R.sub.x )/(k + R.sub.x + R.sub.t)) being substantially linear as a function of temperatures sensed by the thermistor between the temperatures T 1 and a temperature T 3 intermediate the temperatures T 1 and T 2 and being nonlinear as a function of temperatures sensed by the thermistor between the temperatures T 3 and T 2 , where k is a constant equal to the voltage between the collector and emitter electrodes divided by the collector electrode current when the transistor is operated in its linear region; a voltage divider coupled across the voltage source and effective to generate a bias voltage; and means effective to couple the bias voltage to the base electrode of the transistor, the bias voltage having a value so as to bias the base electrode of the transistor so that the transistor is operated in its linear region for values of R t between the temperatures T 1 and T 3 and is operated between its linear and saturated regions for values of R t between the temperatures T 3 and T 2 , whereby the magnitude of the voltage at the collector electrode varies substantially linearly as a function of temperature between the temperatures T 1 and T 2 .