GAS PRESSURE THERMOMETERS
This thermometer uses the volume expansion of gases at temperature changes, in particular the proportional gas expansion of inert gases. These gases can cover temperature changes from –260°C through +700°C and are therefore particularly suitable for high or low temperature measurement. In a closed pressure system the internal pressure change will be proportional to the temperature change, i.e. the pressure will increase when the temperature rises.
The measuring system consists of a bulb with its active volume, a capillary, a bourdon spring and a mechanical gear amplifying the movement of the bourdon tube and transforming it into a rotation. Because the capillary connecting the bulb to the bourdon tube can be bent into any shape and can have a length up to 30m, remote measurement can be executed.
Main features of the gas pressure thermometers are
– extreme temperature range for mechanical thermometers
– good precision and very low measuring hysteresis
– especially when oil filled extremely choc and vibration resistant
– non-polluting & non-contaminating because of use of inert gases
– no aging behavior –> very long mean time between calibrations
These features allow the use in cleanest and health sensitive environments (pharmaceutical & food industry) as well as for extreme temperatures under highest vibrations.