Coolant Temperature Sensor

Our human body has to keep a certain range of temperature (37deg C) for healthy daily life. Like our body, an internal combustion engine is designed to be operated optimally under a certain temperature condition. In general, the coolant temperature stays around 90 deg C for an optimal operation of an engine. If the operation temperature stays out of this designed range, the engine can show several kinds of abnormal behavior, such as excessive exhaust emission, engine hesitation, bad start, etc. Therefore, it is very important to keep a designed operation temperature range.

To monitor engine temperature, a temperature sensor is installed on the engine block and its sensing probe is always touching engine coolant in the block. For and precise control of coolant, two or more temperature sensors can also be used, for example one in cylinder head and another in block.

To convert temperature change into electrical signal, we use the principle of electrical resistance value change when the applied temperature changes on a certain metal. To measure the temperature relatively precisely, thermistor is being used which is a special type of resistance made for temperature measurement. There are two types of thermistors, PTC (Positive Temperature Coefficient) and NTC( Negative Temperature Coefficient) and its measurement range is around from -90 deg up to +130 deg C which can cover the operation range of an internal combustion engine.