Design of Linearized Thermistor Connection Circuit Using Modified 555 Timer

• Published in: Sensors & transducers 2012-06, Vol.141 (6), p.17-17
• Main Authors: Narayana, K V L, Rao, Bhujanga A
• Format: Article
• Language: English
• Subjects: Circuit design; Electric potential; Linearity; Methods; Nonlinearity; Programming languages; Simulation; Studies; Temperature; Temperature sensors; Thermistors; Timer circuits; Transducers
• ISSN: 2306-8515; 1726-5479; 1726-5479

Thermistors have high sensitivity which makes them suitable for various applications, but they exhibit a highly nonlinear resistance-temperature relationship which is exponential in nature. This nonlinearity is an important problem and a lot of research has been dedicated to correct it. In this paper a virtual instrument has been developed based on the modified 555 timer circuit using Lab VIEW to obtain a linearized characteristic over a wide temperature range (0 °C to 120 °C) with reasonably good response linearity, reliability, and overall improved performance. The possibility of developing the proposed instrument as a temperature sensor with frequency as output has been investigated through simulation. It has been shown that the linearization of the thermistor characteristic is achieved by selecting the suitable parameters of the thermistor, the frequency determining elements and the control voltage of modified 555 timer circuit without connecting any additional elements. In a specific range of temperature the proposed circuit is characterized by high temperature stability, improved sensitivity and nonlinearity of about ± 1 %. [PUBLICATION ABSTRACT]