KOSEN 한인과학기술자네트워크

>Ratiometric Temperature Detector 회로 설명 부탁드립니다.>>>>math type 수식이 사라지네요.>(첨부화일 참고해주세요) Single-ended ratiometric measurement: In the ratiometric measurements, the signal voltage does not depend on the absolute value for the resistors R1 and R2. Also, as long as the resistors have the same temperature dependency and are at the same temperature, the temperature dependency of the resistors is canceled to the first order. This is a major advantage for the ratiometric measurements as the changes in resistance, due to temperature changes, can be much larger than the changes due to stress. An added complication is that in a realistric manufacturing environment, no two resistors are identical. This will cause sensor offset and the offset will also have non-zero temperature dependency. The compensation of the temperature induced errors is the biggest challenge in piezoresistive sensors. A brute forece approach is to calibrate the sensor in multiple temperatures. This type of calibration is a slow and expensive process. Differential ratiometric measurement: The Wheatstone bridge enables differential measurement of the piezoresistor output, thus removing the dc offset. By taking the difference in voltage divider outputs, the dc offset is canceled and the output is proportional to the relative resistance change. As the offset is removed at the sensor level, the measuring electronics is simplified. The output is not dependent on the absolute resistance. The added benefits of the differential measurement are increased sensitivity, increased linearity, and the removal of large dc offset. The Wheatstone bridge may also be biased with a constant current I instead of the more common voltage bias. The benefit of the constant current bias is that the output is more linear in comparison to the voltage bias.