It is all too common that engineers under develop thermistor signal conditioning, although it is amongst the easiest of applications. When designing NTC (negative-temperature coefficient) thermistors that are housed in embedded systems with a processor and analog-to-digital converter you must take certain precautions. Below, we want to go over a few dos and don’ts for creating thermistors.
Don’t
Avoid linearizing your analog circuits. Linearization is considered the usage of additional circuitry in order to produce a voltage that provides a more linear function for temperature. When working with analog circuits, linearization is regarded as a necessity. In specific embedded systems, the process should not do linearization in software. There are simple ways to handle the nonlinear conversion of ADC counts to temperature.
Do
Make sure you understand your requirements. This is one of the most important aspects to understand in terms of design. This is the case for all circuits, not just thermistors. Of all the things to consider, the three most important things are:
Accuracy is difficult to analyze because there are many contributing factors, but the most significant cause is the accuracy of the thermistor itself. Most thermistors have a 5% resistance tolerance (at 25 C). Inherent temperature error is the relative accuracy that is divided by a thermistor’s temperature coefficient.
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