Interpretation of the structure and principle of the pressure thermometer

Pressure thermometers are not unknown to those who often use thermometers;

Why, because it is also an expansion temperature sensor.

What is an expansion temperature sensor?

In simple terms, it refers to the reaction temperature of the change in volume or size after the material expands when heated, but if you think so, you\'re wrong;

Actually the real principle is a temperature sensor which uses the principle that the pressure of a liquid or gas in a closed container increases with the expansion of the heat to measure the temperature

You do not know, indeed, a pressure thermometer The structure of the sensor is mainly a closed system composed of three parts: a bulb sensitive to the temperature, a capillary tube, and a monocoil spring tube (or multi-coil spiral tube).

The element uses a spring tube, and the internal cavity of the temperature bulb, capillary tube and spring tube is easy to seal;

It is full of working substance, when the temperature bulb is heated, the pressure of the internal working substance increases due to the increase in temperature;

The changed pressure is transmitted to the spring tube through the capillary tube, which deforms the spring tube.

Then, using the transmission system connected to the non-fixed end of the spring tube, the needle is deflected by a certain angle, and the temperature value of the medium measured is indicated on the dial.

As a temperature sensing device, the temperature bulb is directly in contact with the measured medium, and its material has good thermal conductivity and should be corrosion resistant.

Furthermore, the thermal expansion of the amtemperature hen itself should be much smaller than the expansion of its internal working substance, so the coefficient of expansion should be small.

The capillary is used to transmit pressure. The smaller the inner diameter, the greater the transmission distance will be. However, if the inner diameter is too small, the transmission resistance will increase and the latency time will be longer.

Pressure sensitive elements can use spring tubes, bellows or bellows.

The working substance in the pressure gauge temperature bulb can use liquid, gas or vapor.

If gas is used, it is usually chemically stable nitrogen. The measuring range is -100 to 500°C.

The pressure thermometer can be used for temperature measurement and control, to realize power-on or disconnection anotheromatics of the temperature control circuit.

Tag: pressure thermometer