Two Elementary Measurements from One Source: Precise, Drift-Free and Fast

In combination with HYGROPHIL F which is established in the natural gas industry, BARTEC BENKE (Germany) has developed an innovative and reliable measuring system which by measuring the hydrocarbon dew point and the moisture content in natural gas monitors two risk factors of every natural gas plant.

The sensor element of the HYGROPHIL HCDT is based on the most precise standard method - the chilled mirror principle. During the process, the light signal is not guided through the gas flow as with conventional mirror hygrometers, but it is coupled in the mirror surface from below and totally reflected within the gas. A small area is optically treated in such a way that the light is coupled out there as long as no condensation takes place. The sensor glass is cooled via a Peltier element until the first longer-chained hydrocarbons condense. Smallest amounts are sufficient in order to reflect the light back into the glass which was originally coupled-out at the interface between the condensation film and the gas, thus guiding it to the photodectector. At this point, the temperature is taken up by means of a precise Pt1000 temperature sensor which is vapour-deposited on the sensor glass and frames a decisive area for the measurement.

A measured value drift can be excluded as platinum temperature sensors are considered to be drift-free and neither movable nor easily wearing out sensor components have been integrated. This is why the sensor does not require a cyclical recalibration. Another advantage of the BARTEC design over conventional technology is the fact that particles carried along in the gas have no influence on the measurement. As the condensation range of the sensor has only a size of two square millimetres, the heating and cooling processes at the Peltier element can be carried out very quickly.

Moisture measurement used in the measuring system has also been consistently developed further. The implemented calculation in accordance with DIN EN ISO 18453 represents the currently most reliable mathematical correlation between water content and dew point temperature. The advantage is exact consideration of the gas composition which can be conveniently entered into the evaluation device. Regarding this, pre-defined gas compositions according to the DVGW Worksheet G260 can also be selected.