Temperature gauges measure the thermal state of a homogeneous substance. The measuring system must be brought as closely together as possible with the body to be measured. The most widely used measuring methods rely on temperature-dependent physical and material characteristics.
Machine glass temperature gauge
These temperature gauges are suitable for the monitoring of temperatures in gases, vapours and liquids in vessels and pipelines. The thermometer is housed in a case with a cutout for the scale display. Machine glass thermometers are often used with a V-shaped case.
Bimetal temperature gauge
Temperature gauges operate with a measuring system in the form of a helical or spiral tube. The mechanical deformation of the bimetal strips into the tube shapes mentioned above results in a rotational movement, caused by temperature changes.
Expansion temperature gauge
Wherever the process temperature has to be indicated locally and, at the same time, limit values must be monitored, thermometers with switch contacts find their application. The switch contacts make or break the circuit dependent upon the pointer position of the indicating measuring instrument. If the reading is significantly above or below a set value, they trigger an alarm, hence also the term “alarm contact”. The instruments are also suitable for starting, stopping or switching processes.
Gas-actuated temperature gauge
With a gas-actuated temperature gauge the stem, the capillary and the Bourdon tube are joined together into one unit. The instrument is filled with inert gas. If the temperature changes, the internal pressure will also change.