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Temperature sensing

To build a feedback controller, you'll need a way to measure the error. This measurement is done by the sensor! In this case, we're controlling a temperature system so we need a temperature sensor. Theres a few options out there, each one good for certain applications, so we'll go through the different kinds and what we can expect

But first...

A note about 'precision'!

The feedback controller uses the error in the output to determine what action to take. That means that the error has to be as 'correct' as possible. Its way more important to spend $ on a good temperature sensor than on a controller or heater. (Not that those are not important things either but if you had an extra $1…) Why? Because if your sensor accuracy varies by ±2°C then it doesn't matter too much if your controller has 0.1°C precision.


This is what most people mean, its how close the sensor is to "Real Temperature". If a sensor is inaccurate to ±1°C that means that a measurement of 25°C (assuming everything else is perfect) could be anywhere between 24-26°C

Something that is inaccurate can sometimes be 'fixed' by calibrating it against a precise/accurate sensor.


Precision is how 'repeatable' that measurement is - so if you have that ±1°C accuracy sensor and its precise to 0.1°C then a measurement of 25°C could 'really' be 24.3°C (because thats within the accuracy) but every time you get a reading of 25°C it will be no greater than 24.4C or smaller than 24.2°C

If a sensor is imprecise, theres really not much you can do about it. A precise but inaccurate sensor can be calibrated, but each one must be calibrated individually since the inaccuracy changes from one to another.

/home/ladyada/public_html/wiki/data/attic/tempcontroller/sensor.1267652576.txt.gz · Last modified: 2016/01/28 18:05 (external edit)