Electronics lessons: The Thermistor

I thought I'd go a bit more back to basic in the next few lessons, and introduce some components.

One of the very basic components in electronics is the resistor, (that was covered a long time ago.)
Fixed value resistors are good and very useful in a lot of applications, however, you find that other times you need something that will alter in response to external stimulus.

Say something like a resistor that could sense the temperature?

Well this exists, it's called a thermistor.

It's a small component with two legs, in a bead shaped package (usually) it also usually has some banding around it that specifies what sort of thermistor it is.

Thermistors generally come in a variety of types the different types are able to handle different temperature ranges, but more importantly they set the nominal values of the thermistor.

If you're dealing with incredibly low signal electronics, a thermistor that operates in a range of Megohms may not be appropriate.

On the other hand, if you're using very large voltages, a small thermistor may have to disipate a lot of power and also would not be appropriate.

Thermistors generally work that the warmer they get, the less resistive they become, and the colder they get the more resistive they become.

Hence if your thermistor sits in a beaker of ice, you may get a very high reading when measuring the component, when the same component sits in a beaker of boiling water a much lower reading whoulf be expected.