Based on thermal dispersion technology, Thermatel TD1/TD2 switches from Magnetrol are easily adjusted to detect flow of gases and liquids, level or liquid-liquid interface. With continuous diagnostics, automatic temperature compensation, narrow hysteresis and fast response time, they provide a new level of performance and reliability not found in previous switches. The switches can be used for high level alarm in natural gas filters that are found in gas compressor stations, in extraction fields or to clean the extracted natural gas. On each filter a two level sensor (warning high level & alarm high level) is needed. For this application two TD1 switches can be utilized. The TD1 switch can operate under heavy conditions: typically for such a filter system high static pressure (around 150 bar) and a rather specific medium (natural gas condensate in combination with sand & other waste). However the TD1 switch can operate from -70 up to +450 °C and can handle pressures up to 410 bar. The TD1 uses a constant power to the sensor, meaning calibration can be performed easily and quickly. The built-in temperature compensation reduces the effect of sudden process temperature changes to a minimum and thus offering the benefit of a very fast response and highly repeatable operation. The switch also has a local error indication via a blinking LED. The TD2 switch has all the features of the TD1 switch but can also send a mA error signal to the control room. This is very beneficial in critical service applications where the user needs to be assured the switch is operational. Another feature of the mA output is the possibility for trending and diagnostics providing a repeatable trend indication of the flow rate.