How to address the inaccuracy in measuring hydrogen with a thermal mass flow meter

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　　Thermal mass flow meters are widely used for measuring gases, but like other flow meters, they can also produce errors during measurement. Some time ago, customers asked us why the thermal mass flow meters they purchased gave inaccurate readings for hydrogen. Our factory’s technical staff provided the following response based on the customer’s description. 　　Hydrogen is a very special gas. Due to its low density, its composition changes easily with temperature and pressure. Being an explosive gas, it is easy for the measurements taken of hydrogen to contain errors. 　　For measuring a special medium such as hydrogen, a thermal gas flow meter is a good choice; this is mainly because thermal mass flow meters have a clear advantage over other types of flow meters in terms of measurement accuracy and wide range capability. 　　Regarding the issue of inaccurate measurements reported by the customer, the technicians identified several possible causes: 1. There are still impurities or water vapor in the medium, and debris upstream of the flow meter’s probe sticks to these substances, interfering with the data transmission from the sensor. 　　2. Thermal gas mass flow meters require regular maintenance. Under relatively clean operating conditions, they can be used for half a year to 1 year before the sensor probe needs to be removed and cleaned with clean tissue or a cloth. In more harsh operating conditions, the probe should be cleaned every half a year or 3 months at the latest, in order to ensure measurement accuracy. 　　3. Some instruments need to be sent back to the factory for re-calibration. 　　The above is the analysis by the manufacturer’s technical staff of some on-site issues raised by the customer. For measuring special gases such as hydrogen, thermal mass flow meters are indeed a good choice. However, the flow meter must be regularly repaired and maintained.