Diode Sensing
Electronic temperature measurement relies on the predictable relationship between the forward voltage of a p-n junction and its absolute temperature. This junction thermometrics technique is commonly used to compensate for the thermal sensitivity of silicon pressure sensors. It provides a localized reading directly on the silicon die where the measurement occurs.
The accuracy depends on maintaining a constant current through the diode.
Voltage Characteristic
The voltage drop across the junction decreases by approximately two millivolts for every degree Celsius rise in temperature. In the field of junction thermometrics, this slope is highly linear over a wide range. Precision circuits measure this small change to calculate the current temperature of the chip.
Circuit Integration
Integrating the temperature sensor onto the same wafer as the pressure bridge eliminates the thermal lag found in external probes. Because junction thermometrics provide real time data, the microprocessor can adjust the pressure reading instantly. This integration reduces the overall size of the sensor package.
Thermal Response
The low mass of the semiconductor junction allows it to follow rapid temperature fluctuations. While junction thermometrics are excellent for compensation, they are sensitive to light and electromagnetic interference. Shielding is required to prevent these external factors from corrupting the temperature data.
