International Journal of Advances in Scientific Research and Engineering (ijasre) E-ISSN : 2454-8006 DOI: 10.31695/IJASRE.2020.33854 Volume 6, Issue 8 August - 2020 www.ijasre.net Page 35 Licensed Under Creative Commons Attribution CC BY-NC NTC Thermistor Performance and Linearization of its Temperature- Resistance Characteristics Using Electronic Circuit K.T. Aminu, A. G. Jumba, A. A. Jimoh, A. Shehu, B. D. Halilu, S. A. Baraza, A. S. Kabiru, and M. A. Sule Department of Electrical Engineering Abubakar Tatari Ali Polytechnic Bauchi Nigeria _______________________________________________________________________________________ ABSTRACT This paper critically discusses the performance of an NTC thermistor sensor in the temperature range 20 o C to 85 o C and provides a technique for linearization of the temperature sensed by the thermistor. The linearization was achieved by utilizing Wheatstone bridge electronic circuitry which responds to the thermistor and produces an output which is an exponential function of the temperature sensed by the thermistor sensor. A further simple and low-cost electronic circuitry responds to such output and converts the resistance measurement to provide a signal which represents the temperature. Moreover, the Wheatstone bridge signal conditioning circuitry was designed to have 0 – 100 mV output voltage within the considered temperature range. The physical characteristics of the thermistor (constant A and b) were found to be 4.0015 x 10 -5 ± 0.2956 x 10 -5 Ω and 3514.8 ± 11.6 K respectively. The result also shows that the percentage nonlinearity was as low as 1.7 and a sensitivity value of 1.5661 mV/K was found for the thermistor, but the resolution of this thermistor sensor is 2 o C. However, the percentage of nonlinearity obtained was in agreement with the theoretical percentage nonlinearity. Keywords: Temperature measurement, Thermistor sensor, Practical design, linearization, Nonlinearity. _______________________________________________________________________________________________ 1. INTRODUCTION In the recent decades, thermistor has been widely used for temperature measurement among a variety of applications. Nevertheless, however, one of the most significant discussions in thermistor is that it is a piece of semiconductor made from oxides of metal such as cobalt, iron, nickel, manganese, chromium and uranium pressed in into small wafer, disk, bead or other shape fused at high temperatures and ultimately coated with glass or epoxy and produced in the form of thick films, thin films and pellets [1] [2]. There are two types of thermistors namely: PTC (Positive Temperature Coefficient) and NTC (Negative Temperature Coefficient). The PTC thermistor has its resistance increasing with increasing temperature. Conversely, the NTC thermistor has its resistance decreasing with increasing temperature. However, the NTC thermistors are the most commonly used type than the PTC thermistors, particularly for temperature applications [3] [4]. Figure 1 depicts the NTC thermistor Resistance-Temperature characteristics curve. As far we know, thermistor sensors are very useful temperature measuring devices because of their high sensitivity, high stability, repeatability, and large temperature coefficient of resistance so that variations in the thermistor’s resistance provide a relatively high sensitive temperature sensing operation. On the other hand, one of the significant problems in using thermistors, however, is that the relationship between the resistance and that of the temperature is a non-linear one although such relationship can be expressed by a well known equation. Therefore, in order to make use of thermistors over a wide range of temperature variations it is been found effective to pre-determine the resistance- temperature relationship in accordance with such equation over a relatively wide range of temperatures and then the