A Study of Self-Heating Effect Correction Methods for NTC Thermistors

Correcting for self-heating effects is crucial for minimizing uncertainties in negative temperature coefficient (NTC) thermistor thermometer measurements. This study examined a self-heating effect correction method for NTC thermistors at the triple point of water (TPW) and a water bath under varying currents. The resistance-temperature characteristics of the thermistors over a temperature range of $- 5~^{\circ }$ C to $35~^{\circ }$ C were determined. Both two-current and multicurrent methods were applied to correct the self-heating effects in the thermistors. The results showed that excessive excitation current hindered accurate self-heating correction, while a minimal current would result in a high signal-to-noise ratio, with a recommended test current below $20~\mu $ A. Moreover, optimizing the current ratio in the two-current method significantly reduced the measurement uncertainty. The multicurrent method further reduced the uncertainty, even though this reduction diminished as the number of excitation currents increased. The multicurrent method increased the measurement time and experimental complexity. The self-heating effect and its uncertainty reduced with increasing temperature. Considering both measurement uncertainty and ease of implementation, an improved two-current method with a current ratio of 1:2 is suggested for the accurate measurement and correction of self-heating effects in thermistor thermometers. The self-heating effect from the measured resistance value across all temperature ranges should be corrected to ensure accurate and precise temperature measurements.