On 2018-08-08 14:48:54
temperature transmitter working principle
A sensor designed on the principle of metal expansion
The metal will produce a corresponding extension when the ambient temperature changes, so the sensor can convert the signal of this reaction in different ways.
Bimetal chip sensor
Bimetallic sheet is composed of two pieces of metal with different expansion coefficient. With the change of temperature, material a has higher expansion degree than another metal, which causes the sheet to bend. The curvature of the bend can be converted into an output signal.
Bimetal rod and tube sensors
With the increase of temperature, the length of metal tube (material a) increases, while the length of non expansion steel rod (metal b) does not increase, so the linear expansion of metal tube can be transmitted due to the change of position. In turn, this linear expansion can be converted into an output signal.
Sensor for the design of deformation curve of liquid and gas
When the temperature changes, the volume of liquid and gas will change accordingly.
A variety of structures can transform this expansion change into a position change, thus generating a position change output (potentiometer, inductive deviation, baffle, etc.).
The resistance of metal changes with temperature.
For different metals, the change of resistance value is different for each degree of temperature change, and the resistance value can be used as the output signal directly.
There are two types of resistance changes:
1. Positive temperature coefficient
Temperature rise = resistance increase
Temperature reduction = resistance reduction
2. Negative temperature coefficient
Temperature increase = resistance decrease
Temperature decrease = resistance increase