Thermal conductivity sensors react much more sensitively to hydrogen than to methane. So we are dealing with an over proportional reading. However, there is a very different behaviour of the sensors on hydrogen in larger concentrations. This can go so far that the signal reverses and becomes negative for some sensors in a certain concentration range. It is therefore not guaranteed that every type of thermal conductivity sensor is suitable for the reading of hydrogen in the range between 0 and 100 percent by volume.
The thermal conductiviy sensor of the SIGI-EX reacts uniformly much more sensitive to hydrogen than to methane. Already approximately 20 vol% hydrogen is displayed as 100% methane. For a mixture of natural gas and hydrogen it depends on other components in the natural gas, such as ethane, propane and butane. As gases that are heavier than air, these proportions will weaken the positive signal of hydrogen or will negatively counteract the positive signal.
The thermal conductivity sensor of the OLLI reacts undefined to hydrogen. This means that especially in the range between 4 and 20 vol% hydrogen one cannot say for sure if the sensor detects it reliably.
Below you will find information on the reactions of our device series to hydrogen. Please note that this is the typical reading behaviour, which may vary within a range. We cannot therefore name fixed conversion factors with which a correct measured value could be determined.