Ntc thermistor nonlinearity compensation using wheatstone bridge and novel dual-stage single-flash piecewise-linear adc

Abstract

NTC thermistors are frequently used low in cost temperature sensors which provide some of the most desirable sensing features. However, due to the nonlinear static transfer function their sensitivity decreases with temperature increase, causing lower measurement accuracy in some regions of the measurement range. This paper proposes a method for NTC thermistor nonlinearity compensation using a Wheatstone bridge and a novel dual-stage single-flash piecewise-linear ADC. Both conversion stages are performed using the same flash ADC of a novel design based on a reduced number of comparators employed. In this manner, simpler design, lower production costs, higher compactness and lower power consumption of the linearizing ADC, are achieved. The proposed linearizing method is tested on the Vishay NTCLE413E2103F520L thermistor, in the range from 0◦ C to 100◦ C, and the obtained results confirmed the effectiveness of the method in measurement accuracy improvement: when the flash ADC of 10-bit resolution is employed the accuracy obtained is 7.4747 · 10−5◦ C.