Temperature measurement with cheap NTC's
Thermistors provide a simple and inexpensive way to measure temperatures. They are resistors whose resistance change significantly with temperature. Compared with other solutions like the [TP36](http://www.analog.com/en/mems-sensors/digital-temperature-sensors/tmp36/products/product.html] or LM35 IC's, thermistors are cheaper and more accurate. They can work at any voltage, they are very robust and can be simply powered from an output pin.
Among thermistors, NTC's (Negative Temperature Coeficient) are easier to use for temperature measurements whilst PTC's are mostly used in switching applications. The downside of thermistors is that they are not linear so look-up tables or more complex formulas have to be implemented in order to transform voltage (or resistance) into temperature readings. For this aplication we will apply the Steinhart–Hart equation wich will release us from having to create our own look-up table.
The simplest thermistors circuit consists of a thermistor and a series resistor. We are using the following parts in our example:
- 10 Kohm 1% thermistor
- 10 Kohm 1% series resistor
