Thermistors are special solid temperature sensors that behave like temperature-sensitive electrical resistors.There are basically two broad types,NTC-Negative Temperature Coefficient,used mostly in temperature sensing and PTC-Positive Temperature Coefficient,used mostly in electric current control. They are mostly very small bits of special material that exhibit more than just temperature sensitivity.They are highly-sensitive and have very high reproducibility with resistance Vs. temperature properties. Thermistors,since they can be very small in size,are used inside many other devices as temperature sensing and correction devices as well as in specialty temperature sensing probes for commerce,science and industry. Thermistors typically work over a relatively small temperature range,compared to other temperature sensors and can be very accurate and precise within certain range.