A linear temperature-to-frequency converter
Leif Løvborg · Journal of Scientific Instruments · 1965
The possibility of converting temperature into a frequency signal by means of a thermistor which is part of the frequency-determining network of an RC oscillator is investigated. It is shown that a temperature-frequency characteristic which has a point of inflection may be realized, and that the maximum value of the temperature-frequency coefficient β in this point is - 1/3 α, where α is the temperature coefficient of the thermistor at the corresponding temperature. Curves showing the range in which the converter is expected to be linear to within ±0.1 degC are given. A laboratory-built converter having β = 1.0% degC -1 at 25°C is found to be linear to within ±0.1 degC from 10 to 40°C.