How A Thermal Mass Flow Meter Works

The use of specialized meters to monitor the flow of gas or liquid through a system is critical in many areas of production, processing, manufacturing throughout a wide range of industries and facilities. The ability to monitor the flow of liquids and gas through a system is critical for safety, efficiency and system integrity.

The most common option for this type of low-pressure gas and liquid flow systems is a thermal mass flow meter. Compact, durable and very accurate, they offer an accuracy in reading which offers benefits to other types of volumetric flow meters. It is important to note; it is possible to read gas pressures of less than 25 feet per minute with this flowmeter, which is not possible with other types of meters for the accuracy required.

The choice of a thermal mass flow meter means the ambient conditions, including the condition of the media in the system, will not impact the readings of the meter. The reading will not be affected by changes in pressure, density, viscosity or temperature internally or as ambient factors in the working environment.

The Process

As the name implies, these meters use the application of a known amount of heat introduced into the flow of gas or liquid. A probe located in the stream measures the temperature change to calculate the flow. The other option is for the probe to be maintained at a pre-set, consistent temperature and the measurement of the energy required to keep the temperature at the constant rate is measured.

For very large volume of flow, there is a bypass-type of option in the thermal mass flow meter. This flow meter has a capillary tube which is used to measure the change in temperature with a small volume of the stream, creating a highly accurate measurement which would be impractical and impossible in a large flow volume.

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