2. Gas-in-Metal Expansion Thermometers

2.1 Principle

Gas-operated thermometers are made of gas-filled cylinders at high pressure with pressure-sensitive pressure gauges and temperature indicators. The change in gas pressure inside the sphere caused by temperature changes is detected by a special helicoil bourdon tube connected to the amplifier, and this change in gas pressure will change the movement and pointer in proportion to the change in temperature. In other words, the temperature system consists of a case containing a temperature sensor, a transmission capillary and a bourdon tube element. The system is pressure-filled with suitable surrogate elements. This is pressurized with an inert gas. This change in temperature will affect the internal pressure of the system. This pressure change is measured by the Bourdon tube and displayed on the dial scale in terms of temperature units. The influence of ambient temperature is compensated by the bimetallic device, which is the case. The physical characteristics used will be able to read linearity from the beginning of the dial to the full range. When the installation of the gauge is away from the measuring position, the capillary tube is used to transfer the value of the change between the stem of the cylinder and the head and sphere of the thermometer. Capillary tubes are commonly used in industrial environments. Gas-in metal expansion thermometers are available in -200… with accuracy according to Class 1 of DIN 16203. Temperature measurements up to 800 ° C are possible.

2.2 Application

The gas expansion thermometer is equipped with a temperature compensation device. It is maintained at ambient temperatures between 50 ° C and has an accuracy of 1% on its own. Designed for industrial applications requiring good accuracy, these thermometers have natural measurements for the following reasons:

-No power supply required

-The value can be read even if it is far from the desired temperature measurement position.

-Robustly designed

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