Explain the working principle of temperature sensors?
Answer:
There are several types. They all, generally, measure the difference between sometshing measured, and some standard. A simple example of a high temp sensor is a thermocouple which is two different types of wire that are twisted together at each end. The principle is based on the idea that dis-similar metals in contact generate different voltages at different levels of thermal excitement.
Once the types of metal are known, then volts per degree of temp difference on each end is known, and then your "standard" is one contact area where you know the temp, and the sensing end is a contact area in the hot (or cold) substance. The voltage difference between the ends is a relative measure of the temperature at the sensing end compared to the voltage at the standard end. The bigger the temp difference, the bigger the voltage difference..
Ron.
Thermocouples are bi-metal devices that produce current in response to temperature. Thermistors change their resistance in response to temperature. Pyrometers read levels of IR emission in response to temperature. These are the three mot commonly used sensing devices.
There are many different types of temperature sensors that work on different basic principles.
Of the sensors listed below the IC temperature sensor is the most simple to use as the “conditioning circuit” is part of the same low cost package as the sensor and the output of the device is linear (often specified in degrees C (or degrees F) per millivolt. This type of sensor generally uses some part of a diodes IV curve (which is temperature dependent). These sensors have become prevalent in PC’s to monitor the CPU termperature.
Thermocouples -- http://en.wikipedia.org/wiki/thermocoupl...
Thermistors -- http://en.wikipedia.org/wiki/thermistor...
Integrated circuit (based on reversed biased diode junction) –
http://en.wikipedia.org/wiki/silicon_ban...
http://www.electronicproducts.com/showpa...
http://www.maxim-ic.com/appnotes.cfm/an_...
RTD (resistance of a metal – often platinum) -- http://en.wikipedia.org/wiki/resistance_...
Pyrometers -- http://www.omega.com/pdf/temperature/z/p...
http://www.omega.ca/pdf/temperature/z/zs...
There is a lot of information in these links.
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