A temperature gauge is used to measure the force of heat in a machine or application. The gauges, commonly known as thermometers, measure heat in different ways depending on the type. Here, MGA Controls discusses the difference between bi-metal industrial thermometers and gas thermometers, outlining the advantages of both.
How does a bimetal thermometer work?
A bi-metal thermometer, also known as a bimetallic dial thermometer provides an accurate temperature measurement, through a bimetallic sensing element reacting to temperature change. The bimetal thermometer is made up of two metals moulded together to form a coil. As the temperature changes, the bimetallic coil contracts or expands, causing the pointer to move up or down the scale. In turn, this creates a reading, illustrating the temperature.
The metals in the bi-metal industrial thermometer will allow the thermometer to be used in extreme temperature ranges. The most common metal elements include stainless steel and brass, measuring a wide temperature span from -70 to +600°C. The different metal compositions allow the coil to contract and expand, allowing a reading to be taken from the temperature gauge.
Advantages of a bi-metal thermometer
Bi-metal thermometers are often used in hazardous applications and are available with ATEX protection, maximising their ability to withstand corrosive environments and aggressive media. The case design (with protection ratings up to IP68) guards the thermometer against outside elements coming into the pressure gauge, such as water or dust ingress, allowing it to function well in outdoor environments.
A common bi-metal industrial thermometer, stocked at MGA Controls is the Bourdon TBI Series, they boast a stainless steel casing, allowing them to withstand maximum temperature ranges of -70 °C to 600°C. They are also available with ATEX features and boast a protection class of IP67.
Gas thermometer uses
A gas thermometer, also known as a gas expansion or gas-actuated thermometer is capable of measuring a wide range of temperatures. There are different types of gas thermometers, however, their working principle is very similar. The gas thermometers use a small volume of gas in a tube in order to determine the temperature in an application or machine.
The Bourdon TSF Series is one example of a gas-filled thermometer, available at MGA Controls. The thermometer measures temperature either by a rigid tube or flexible capillary inserted into a Thermowell. The temperature is accurately measured by the gas inside the thermometer expanding and contracting in relation to the temperature.
Advantages of gas thermometers
Gas-filled thermometers have multiple advantages, including their ability to span a wider temperature range than bi-metal thermometers. A gas thermometer can measure temperatures ranging from -200°C to +800°C. Gas thermometer advantages also include a capillary length of up to 30m and can have additional ATEX protection fitted for hazardous areas.
View our range of Gas Actuated Thermometers