Mass Measurement

Mass flow measurement of gases

November 2018 Mass Measurement

The Kobold MAS mass flowmeter works according to the calorimetric method and was conceived for gas flow measurement. Since gases can be compressed, the volume changes with pressure and temperature. In practice this means that calibration should be done for a particular working pressure and temperature. This conversion is not needed with the MAS device because the mass flow of the gas is determined by measuring the heat transfer.

The gas is led through a laminar-flow bypass and due to the pressure difference that arises a small quantity of gas branches off into the measuring pipe. With laminar flow, the distribution ratios of both gas quantities remain constant, which is important for the calculation of the flow volume. There are two temperature measuring points (RTD elements) in the measuring tube arranged in sequence (one behind the other). The gas flowing through is subjected to a constant amount of heat. The gas molecules absorb that heat and carry it away. This creates a temperature difference between the sensors that increases with the amount of gas flowing. The temperature difference creates a resistance difference in the RTD elements. It is now only necessary to convert the temperature difference into the standard mass flow. A rotating LCD display shows the corresponding volume flow in standard units per minute. The digital display makes it virtually impossible to make a reading error.

Typical applications are in process control, laboratories, gas display tables, OEM applications, leakage rate testing, filter monitoring and gas flow calibration. The sophisticated measuring procedure and modern electronics in the MAS greatly simplifies the measurement of gas flow.

For more information contact Instrotech, +27 10 595 1831,,


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