Temperature and Embedded Systems
Embedded systems have long been used to monitor temperature. There are number of temperature sensors in the market for this purpose. These range from black body detectors to resistance sensors. A common type is the negative temperature co-efficient or NTC thermistor. Actually, there are two types of thermistors which differ by their resistance to temperature.
In a NTC thermistor, the resistance decreases as the temperature increases. On the other hand, in a positive temperature coefficient thermistor, the resistance increases as the temperature increases.
To put it more simply, a PTC thermistor is used as a protection device and a NTC thermistor is used as a thermal sensor. They can also be divided into non-contact and contact temperature sensors. Non-contact sensors measure the thermal radiation emitted by a heat source to determine temperature, while a contact sensor (thermistors and thermocouples) must be in touch with the object whose temperature they want to measure. Both NTC and PTC thermistors come under the latter category.
These temperature sensors are used in HVAC environment control tools, food processing, chemical handling, medical devices and in automobiles. An embedded designer must know the various types and uses of temperature sensors because he/she will probably have to deal with some varieties in his/her career.