Bias current modulation eliminates wiring errors

摘要

Diodes make good temperature sensors because they are inexpensive, robust, stable, and sensitive, and they don't need reference junctions. Diodes require an excitation current to produce a PN-junction voltage, which varies with temperature by -2 mV/℃. The excitation current causes voltage drops in measurement wires because of a wire's resistance. You need to compensate for those voltage drops so that the measurement will accurately represent the diode voltage.rnMany circuits remove the excitation current from the measurement using a four-wire Kelvin connection: Two wires carry the excitation current, while the other two wires connect the sensor to an ADC (analog-to-digital converter) or measurement instrument. But by using a modulated excitation current, you can use just two wires and still remove the losses in the wires.