One tool for measuring temperature is the bimetallic thermometer. Using a copper aluminium bimetal strip, it transforms the temperature of the medium into mechanical displacement. The bimetallic thermometers consist of two distinct metals with dissimilar thermal expansion coefficients.

Bimetallic thermometers find application in both domestic and commercial settings, including air conditioners, ovens, heaters, hot wires, refineries, and more. They are an easy, reliable, and reasonably priced method of measuring temperature.

Building and Planning

Two fundamental metal characteristics are used by a bimetallic thermometer to function:

• The metal’s capacity for thermal expansion
• For a given temperature, various metals have varying coefficients of thermal expansion.

The bimetallic strip is the primary part of the bimetallic thermometer. The bimetallic strip is made up of two thin metal strips with distinct coefficients of thermal expansion. A metal’s ability to alter volume or form in response to temperature changes is known as thermal expansion. The metal strips are fused or riveted together along their length. On one end, the strips are fixed, whereas on the other, they are free to move.

Benefits and Drawbacks

The following are some benefits of bimetallic thermometers:

• Sturdy and simple design
• Less costly than alternative thermometers
• Since they are entirely mechanical, they run without a power supply.
• Simple upkeep and installation
• Almost linear reaction to variations in temperature
• Ideal for a broad variety of temperatures

The following are some drawbacks of bimetallic thermometers:

• It is not advisable to use them in extremely hot weather.
• They might need to calibrate often.
• Could provide an inaccurate low-temperature measurement.
• Rough handling throws off the calibration.

Bimetallic Thermometer Types

Helix strip bimetallic thermometers and spiral strip bimetallic thermometers are the two varieties of bimetallic thermometers. The purpose of the helix and spiral strips is to maintain a controllable thermometer size.

Bimetallic thermometer with helix strip

This kind of thermometer uses, as its name implies, a helix-shaped bimetallic strip to monitor temperature. At the strip’s free end, the pointer attaches via the shaft.

Bimetallic thermometer spiral strip

A bimetallic spiral strip thermometer, as shown in Figure 4, uses a spiral-shaped strip to monitor temperature. The two metal strips expand in distinct ways with increasing temperature. As a result, the strip bends and coils, forming the outer edge of the arc from the metal with a greater thermal coefficient.

Selection Standards

The bimetallic thermometer that best suits your application will be determined by taking into account the following selection criteria:

Temperature range: Both the upper and lower limit temperatures should reach the bimetallic thermometer

Stem: The bimetallic stemmed thermometer’s length and diameter should be based on the needs of the application. Thus, determining the immersion length or depth of the tank in which the thermometer will be useful may be necessary for this.

Thermowells: In industrial applications, temperature sensors are mainly in protection by cylindrical tube fittings, and thermowells.

Type: The bimetallic thermometer is a type of thermometer that can feature a spiral or helix strip by copper aluminum bimetal busbar manufacturers. However, the helix strip thermometer is the recommended choice for industrial settings, including oil burners and refineries.