Remote temperature measuring system with semiconductor junction sensor

A temperature measuring circuit for measuring the effect of temperature on the voltage drop across a semiconductor junction sensor located remotely from the measuring circuit wherein the measuring circuit is connected to the sensor by a pair of conductors having lead resistance, comprising;

• a programmed current source connected to the conductors for alternately providing to the sensor first and second currents I.sub.1 and I.sub.2, respectively, having a fixed ratio (I.sub.2 /I.sub.1) thereby producing first and second voltages respectively across the conductors wherein said voltages each include a lead component arising from the lead resistance and the respective current,
• means for sampling and holding the first voltage, which voltage includes a lead component I.sub.1 R proportional to the first current,
• means for sampling and holding the second voltage, which second voltage includes a lead component I.sub.2 R,
• amplifier means having a gain of (I.sub.2 /I.sub.1) for multiplying the first voltage by the said fixed ratio (I.sub.2 /I.sub.1) to derive a third voltage having a lead component I.sub.2 R equal to that of the second voltage, and
• means for measuring the difference between the second and third voltages to obtain an output which is free of any lead component and which varies substantially linearly with the temperature of the sensor.