Introduction
A temperature sensor is a device that gathers data concerning the temperature from a source and converts it to a form that can be understood either by an observer or anther device. It measures the temperature of a medium. The sensors are used for different purposes from the simple home use to extremely accurate and precise scientific use.
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Even human and most animals have biological temperature sensors in their body which works as the same function as the artificial does. It collects data and transfers it into a understandable form. For eg, human sensory nerves sends sensory information from the skin to the brain in the form of electrical impulses.
Types
Types: Temperature Sensors measure the amount of heat that produces from the object. It detects the changes of the temperature either as output of analog or digital. The temperature consists of two basic types of features:
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These two basic types of sensors can be sub-divided into the following three groups of sensors, Electro-mechanical, Resistive and Electronic. All these are discussed below:
The 1. Thermostat
: This is a type electro-mechanical temperature sensor, which is consists of two different types of metal; for example nickel, copper, tungsten or aluminum. These are bonded together to make a bi-metallic strip. When this is connected with heat, the different linear expansion of two different metals produces a mechanical bending.
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Snap-action type thermostats are commonly used in our homes for controlling the temperature set point of ovens, irons, immersion hot water tanks and they can be found on walls to control the domestic heating system. But it has large hysteresis range on the opening and closing of electrical contracts. That’s why commercially available bi-metallic thermostats have temperature adjustment screws, by which it is possible to adjust the temperature at desired level and pre-set hysteresis level.
2. Thermocouple
Thermocouples are the most common temperature measuring device. It consists of two dissimilar metals, joined together at one end.
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- Thermocouple is extensively used in steel processing, turbine and diesel engine for temperature measurement
- It is used in gas feed heat appliances such as ovens and water heaters.
- It is used in power production.
- A thermocouple can be used as a vacuum gauge over the range of approximately 0.001 to 1 torr absolute pressure
- Thermoelectric cooling
- Medical equipment and Packaging equipment
2 3. Thermistor:
A thermistor is type of resistor whose resistance varies significantly with the temperature. They are widely used as inrush current limiters, temperature sensors, self-resetting overcurrent protectors and self-regulating protectors.
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http://www.thomasnet.com/articles/automation-electronics/Thermocouples-Types
http://www.facstaff.bucknell.edu/mastascu/elessonshtml/Sensors/TempR.html
http://en.wikipedia.org/wiki/Thermistor
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