In this article, we explain what a thermal mass flow meter is and clarify the working principle of thermal flow measurement.

What is a Thermal Mass Flow Meter?

industrial thermal mass flow meter
The Sage Paramount

A thermal mass flow meter is a precision instrument that measures gas mass flow. The device is used in a wide range of applications in many industries.

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What is the Thermal Mass Flow Meter Working Principle?

thermal mass flow meter sensors
Gas flows by the heated flow sensor and molecules of the gas transport heat away, the sensor cools, and energy is lost.

The thermal mass meter measures gas flow based on the concept of convective heat transfer.

The Sage flow meters are available in either inline flow bodies or insertion-style. In either case, the meter’s probe inserts into a gas stream of a pipe, stack, or duct. Toward the tip of the meter’s probe are two sensors. These sensors are resistance temperature detectors (RTDs) or resistance thermometers and measure temperature. The RTDs consist of durable reference-grade platinum windings clad in a protective 316 SS or Hastelloy C sheath.

One of the RTDs is heated by an integrated circuit and functions as the flow sensor, while a second RTD acts as the reference sensor, and determines the gas temperature. The Sage proprietary circuitry maintains a continuous overheat between the flow sensor and reference sensor. As gas flows by the heated RTD, flowing gas molecules transport heat away from it, and as a result, the sensor cools, and the energy is lost. The circuit balance disrupts, and the temperature difference (ΔT) between the heated RTD and the reference RTD changes. Within a second, the circuit restores the lost energy by heating the flow sensor, to adjust the overheat temperature.

The electrical power required to sustain this overheat denotes the mass flow signal.

What are the advantages of thermal mass flow meters?

  • Thermal flow meters have no moving parts, which reduces maintenance and permits the use in demanding application areas, including saturated gas.
  • Gas mass meters calculate mass flow rather than volumetric flow and do not require temperature or pressure correction, which means there is no additional expense for the purchase and installation of other equipment.
  • Thermal flowmeters provide excellent accuracy and repeatability over a wide range of flow rates.
  • Thermal flow meters can measure flow in large pipes.

Also, see our post “9 Thermal Mass flow Meter Advantages.

Why is measuring mass flow important?

FAQ

What are the benefits of the inline vs insertion flow meter?

There are two major thermal mass flow meter configurations, the inline and insertion styles. Both are often referred to as integral meters.

What are the types of flow meters?

paramount thermal mass flow meter

Gas meter types for flow measurement are categorized as mass flow meters, velocity flow, differential pressure, and positive displacement meters.

Mass flow vs volumetric flow?

While comparing mass flow rate to volumetric flow rate, some distinct advantages for using thermal flowmeters over volumetric meters emerge.

What is the mass flow rate measured in?

gas mass flow rate units of measure

See how gas mass flow rate units of measure relate to the various meter types and learn the difference between volumetric and mass flow rates.

Here is a video describing the thermal mass flowmeter working principle and theory.

6 thoughts on “What is the Thermal Flowmeter Working Principle?

  1. Avatar
    KENNETH GIBBS says:

    I thank u for your explanation of thermal mass flow senor. I work in HVAC. No could explain the principle of operation.

  2. Avatar
    Sara says:

    Very clear explanation. I wonder if the flow meter will reponse well at different flow current or it’s best for a constant flow application. Futhermore, do you have a sales representative in Spain? Regards.

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