Performance Evaluation of Simple Digital Measurement Platform for Remotely-Located RTD Applications

A simple and low-cost digital measurement system suitable for a four-wire RTD sensor is reported in this manuscript. The digital measurement platform suits for the linear estimation of the resistance of the RTD sensor without depending on the connecting wire resistances and their mismatches. In addition, this measurement system requires only four conversion cycles to make the output free from errors, related to the microcontroller voltage-levels. The proposed measurement platform also has the privilege to select the comparator threshold levels. This makes the output of the circuit independent from the tolerance-related errors. The working of the digital platform is mathematically derived and detailed in this manuscript. Later, the effect of possible error sources is also analyzed. The methodology is verified using extensive simulation and experimental studies. A linear transfer characteristic is obtained during these tests, and the measured maximum nonlinearity is 0.38 %. Finally, a short comparison is also performed with the existing techniques for four-wire RTD.