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Temperature Measurement · Glossary

What is a Bimetallic Thermometer?

local dial thermometerTemperature Measurement

A bimetallic thermometer uses a coiled strip of two bonded metals with different expansion rates that turns a pointer as temperature changes.

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Bimetallic Thermometer Explained

When heated, one metal expands more than the other, so the strip bends. Wound as a helix, the bending becomes rotation of the pointer shaft.

Bimetallic thermometers are simple local indicators. Install them in a thermowell, with enough stem immersion for the helix to reach process temperature.

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Calculators for Bimetallic Thermometer

CalculatorThermal Expansion CalculatorFree online calculator with formula and worked example.

Frequently Asked Questions

What is a Bimetallic Thermometer?

A bimetallic thermometer uses a coiled strip of two bonded metals with different expansion rates that turns a pointer as temperature changes.

How accurate are bimetal thermometers?

Commonly about 1 % of full scale; check the class on the data sheet.

Why does the reading lag?

The helix has mass and sits in a well; response is slower than a small sensor.

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Related Terms

Temperature termThermowellA thermowell is a closed end tube fitted into the process that protects a temperature sensor and allows…Temperature termInsertion LengthInsertion length is the length of a thermowell or sensor that projects into the process from the mounting…Temperature termThermal ExpansionThermal expansion is the increase in length or volume of a material as its temperature rises.

More Temperature Measurement Terms

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All temperature measurement terms · Full glossary A to Z

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