Bimetallic thermometer is a kind of field testing instrument for measuring low and medium temperature. It is used especially in industry.


It can directly measure the temperature of the liquid, vapor and gas within -80℃~+500℃ in a variety of production processes. The bimetallic thermometer is made of a metal sheet which is made into a ring and bend shape. When one end is heated and expanded, it will lead to the rotation of the pointer and the working instrument will show the temperature value of the thermal electric potential.

Sino-Inst offers a variety of bimetallic thermometer for industrial level measurement. If you have any questions, please contact our sales engineers.

How Does a Bimetallic Thermometer Work?

The working principle of bimetallic thermometer depends on the two fundamental properties of the metal.The metal has the property of thermal expansion, i.e., the metal expand and contract concerning the temperature.The temperature coefficient of all the metal is not same. The expansion or contraction of metals is different at the same temperature.

What Is WSS Series Bimetallic Thermometer And Its Uses?

WSS series bimetallic thermometer is an on-site detection instrument for measuring low and medium temperature. The bimetal thermometer can directly measure the temperature of liquid, steam and gaseous media in the range of -80℃~+500℃ in various production processes.

What Is The Meaning Of Bimetallic?

They are made up of bimetallic strips formed by joining two different metals having different thermal expansion coefficients. Basically, bimetallic strip is a mechanical element which can sense temperature and transform it into a mechanical displacement. This mechanical action from the bimetallic strip can be used to activate a switching mechanism for getting electronic output. Also it can be attached to the pointer of a measuring instrument or a position indicator. Various techniques such as riveting, bolting, fastening can be used to bond two layers of diverse metals in a bimetallic strip. However the most commonly used method is welding. Since two metals are employed to construct a bimetallic strip, hence they are named so.

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  1. It can display the temperature on-site, which is intuitive and convenient;
  2. It is safe and reliable with long service life;
  3. With a variety of structural forms, which can meet different requirements.

Main Technical Parameters

  • 1.Product implementation standard:JB/T8803-1998
  • 2.Nominal diameter of dial:60,100,150
  • 3.Precision grade:(1.0),1.5
  • 4.Thermal response time:≤40s
  • 5.Protection level:IP55
  • 6.Angle adjustment error Angle adjustment error should not more than 10% of the range
  • 7. Return difference: the return difference of the thermometer should not be more than the absolute value of the error limitation.
  • 8. Repeatability: the repeatability of the thermometer should be no greater than 1/2 of the absolute value of the basic error limitation.


According to the connection direction of the bimetal thermometer dial and the protective tube, the bimetal thermometer can be divided into four types: axial type, radial type, 135°direction type and universal type.

  1. Axial bimetal thermometer: The pointer plate is connected vertically to the protection tube.
  2. Radial type bimetal thermometer: The pointer disc is connected in parallel with the protection tube.
  3. 135°direction bimetallic thermometer: the pointer disc and the protection tube are connected at 135°.
  4. Universal bimetal thermometer: The connection angle between the pointer plate and the protective tube can be adjusted arbitrarily.

WSS-420 WSS-520 WSS-421 WSS-521 WSS-422 WSS-522 WSS-432 WSS-532 WSS-424 WSS-524 WSS-425 WSS-525 WSS-526

Axial type
Axial type

WSS-300 WSS-400 WSS-500 WSS-301 WSS-401 WSS-501 WSS-302 WSS-402 WSS-502 WSS-303 WSS-403 WSS-503 WSS-304 WSS-404 WSS-504 WSS-305 WSS-405 WSS-505 WSS-306 WSS-406 WSS-506

Radial type
Radial type

WSS-310 WSS-410 WSS-510 WSS-311 WSS-411 WSS-511 WSS-312 WSS-412 WSS-512 WSS-313 WSS-413 WSS-513 WSS-314 WSS-414 WSS-514 WSS-315 WSS-415 WSS-515 WSS-316 WSS-416 WSS-516

Universal type
Universal type

WSS-480 WSS-580 WSS-481 WSS-581 WSS-482 WSS-582 WSS-483 WSS-583 WSS-484 WSS-584 WSS-485 WSS-585 WSS-586 WSS-486

Installation Requirements

For the installation of bimetal thermometers, attention should be paid to accurate temperature measurement, safety and reliability, and convenient maintenance, and does not affect equipment operation and production operations. The above requirements must be met. When selecting the installation position and insertion depth of the thermal resistance, the following should be paid attention to A few points:

(1) In order to have sufficient heat exchange between the measuring end of the thermal resistance and the measured medium, the location of the measurement point should be selected reasonably and try to avoid installing thermal resistance near the dead corner of the valve, elbow, pipeline and equipment.

(2) The thermal resistance with protective sleeve has heat transfer and heat dissipation loss. In order to reduce the measurement error, the thermocouple and thermal resistance should have sufficient insertion depth:

  • a. For the thermal resistance measuring the temperature of the fluid in the center of the pipeline, the measuring end should generally be inserted into the center of the pipeline (vertical installation or inclined installation). If the pipe diameter of the tested fluid is 200 mm, the insertion depth of the thermal resistance should be 100 mm;
  • b. For temperature measurement of high-temperature, high-pressure and high-speed fluids (such as main steam temperature), in order to reduce the resistance of the protective sleeve to the fluid and prevent the protective sleeve from breaking under the action of the fluid, the shallow insertion method of the protective tube or the hot sleeve type can be adopted Thermal resistance. For shallow plug-in thermal resistance protection sleeves, the depth of insertion into the main steam pipe should not be less than 75mm; the standard insertion depth of thermal-jacket thermal resistance is 100mm;
  • c. If you need to measure the temperature of the flue gas in the flue, even though the flue diameter is 4m, the thermal resistance insertion depth is 1m;
  • d. When the insertion depth of the measuring original exceeds 1m, it should be installed vertically as much as possible, or a support frame and protective sleeve should be installed.

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