Thermal Mass Flow Meter

What is a Thermal Mass Flow Meter?

Thermal gas mass flow meter is a flow meter that can detect the mass flow of gas without temperature and pressure compensation.

Thermal Mass Flow Meter Unaffected by changes in viscosity, density, temperature, or pressure. Thermal mass flow meters are designed based on the principle of thermal diffusion.

Including natural gas, coal gas, liquefied gas, flare gas, argon, carbon dioxide, and other mixed gas flow measurement.

Thermal mass flow meter specification

Measuring MediumVarious gases (Except the acetylene)
Pipe SizeDN10~DN4000mm
Velocity0.1~100 Nm/s
Working TemperatureSensor: -40℃~+220℃
Transmitter: -20℃~+45℃
Working PressureInsertion Sensor: medium pressure≤ 1.6MPa
Flanged Sensor: medium pressure≤ 1.6MPa
Special pressure please contact us
Power SupplyCompact type: 24VDC or 220VAC, Power consumption ≤18W
Remote type: 220VAC, Power consumption ≤19W
Response Time1s
Output4-20mA (optoelectronic isolation, maximum load 500Ω), Pulse,
RS485 (optoelectronic isolation) and HART
Alarm Output1-2 line Relay, Normally Open state, 10A/220V/AC or 5A/30V/DC
Sensor TypeStandard Insertion, Hot-tapped Insertion and Flanged
ConstructionCompact and Remote
Pipe MaterialCarbon steel, stainless steel, plastic, etc
Display4 lines LCD
Mass flow, Volume flow in standard condition, Flow totalizer, Date and Time, Working time, and Velocity, etc.
Protection ClassIP65
Sensor Housing
Stainless steel (316)

Thermal mass flow meter advantages and disadvantages


  1. No need for temperature and pressure compensation for gas flow measurement. Convenient and accurate measurement;
  2. Wide range ratio, can be used for gas leak detection;
  3. Measuring flow rate range: 0.1Nm/s~100Nm/s.
  4. Good seismic performance and long service life, free from the influence of vibration on measurement accuracy;
  5. Overall digital circuit measurement, accurate measurement and convenient maintenance;
  6. Using RS-485 communication, factory automation and integration can be realized. click for inqueries
  7. No pressure loss, suitable for pipes of any shape with known cross-sectional area.
  8. Corrosion-resistant sensor, suitable for measuring corrosive gas.
  9. It is especially suitable for large-caliber measurement to ensure the accuracy of measurement and is suitable for trade settlement.
  10. The amount of construction is very small. Due to the plug-in structure, it can be installed and maintained online.
  11. The base-type instrument can display on-site and control with alarm.


  1. The thermal mass flow meter responds slowly.
  2. Places where the measured gas composition changes greatly. Due to changes in the cp value and thermal conductivity, the measured value will vary greatly and cause errors.
  3. For small flow, the meter will bring considerable heat to the gas to be measured.  
  4. For thermally distributed thermal gas mass flow meters, if the measured gas deposits a scale layer on the pipe wall, the measured value will be affected. Must be cleaned regularly. The thin tube type instrument has the disadvantage of being easy to be blocked, and it cannot be used under normal circumstances.
  5. The use of pulsating flow will be restricted.
  6. Thermal mass flow meters for liquids are also restricted in the use of viscous liquids.

Thermal mass flow meter applications

The thermal measuring principle is widespread in the industry, and is being used successfully in many applications with gas flow, for example:

  1. Compressed air (consumption, distribution)
  2. Carbon dioxide (for beverage production and chilling)
  3. Argon (in steel production)
  4. Nitrogen and oxygen (production)
  5. Natural gas (for burners and boiler feed control)
  6. Air and biogas measurement (e.g. in wastewater plants)

Thermal mass flow meter for liquids

Generally, Thermal mass flow meters produced in China are used to measure gas mass flow.

If you need to measure liquid mass flow. Please contact our sales engineer. We will provide you with detailed product recommendations.

Thermal mass flow meter installation

Insertion installation:

  1. Position determination: Keep away from elbows, solenoid valves, and other parts to ensure a stable flow field;
  2. Welding of the welding base: drill a Φ22 round hole in the pipe, and weld the welding base;
  3. Install the instrument: put the locking head into the probe rod during installation, and tighten it with a wrench after confirming the insertion depth;
  4. It is recommended that the user adopt a continuous flow ball valve when selecting the model, which is easy to disassemble. Especially in the medium place that is harmful to the human body.
  5. In the caliber smaller than DN300, the insertion depth is 1/2D+15mm. In the DN300-DN1000 caliber, the insertion depth is 1/4D+15mm. Above DN1000, the insertion depth is 1/8D+15mm.

Pipe-segment installation method:

  • Can be installed horizontally and vertically.
  • When installing, first weld the special flange to the front and rear straight pipe sections.
  • Then clamp the front and rear straight pipe sections, gaskets, and instruments with stud bolts and connect them into one.
  • Then install this component on the pipeline. When installing, pay attention to the direction marked on the instrument should be consistent with the direction of the fluid.
Figure 1. Simplified thermal gas mass flow meter-suitable for pipe diameters above DN80 and below DN500
Figure 2. Full-tube thermal gas mass flowmeter-suitable for pipe diameters above DN15 and below DN80
Figure-3.-Standard thermal gas mass flow meter (special models need to be customized)-suitable for pipe diameters above DN80 and below DN4000
Figure-3.-Standard thermal gas mass flow meter (special models need to be customized)-suitable for pipe diameters above DN80 and below DN4000
Figure 4. Flange plug-in gas mass flow meter
Figure 4. Flange plug-in gas mass flow meter


(1) The integrated plug-in type should be inserted into the axis of the pipeline to be tested, so the length of the measuring rod depends on the diameter of the measuring pipe. It should be stated when ordering. If it cannot be inserted into the axis of the pipeline, the manufacturer will provide calibration coefficients to complete accurate measurement.

(2) The one-piece full-tube type adopts the national standard GB/T9119-2000 and is produced in accordance with the GB/T9119-2000 standard. (Other standards will be implemented after consultation and confirmation with the manufacturer.)

This measuring principle is based on the fact that heat is drawn from a heated body when a fluid flows past.

The thermal mass flow meter is a flow meter based on the principle of thermal diffusion.

That is when the fluid flows through the object, the amount of heat loss of the heat-generating object is proportional to the flow rate of the fluid.

Thermal flow measuring principle
SI-RSL Thermal mass flowmeters
SI-RSL Thermal mass flowmeters

Specifically, the flowmeter sensor has two standard RTDs. One for the heat source and one for measuring the temperature of the fluid.

When the fluid passes, the temperature difference between the two is nonlinear with the flow rate.

The meter can convert this relationship into a linear output, that measures the flow signal.

There are two design methods for the flowmeter manufactured, by the principle of thermal diffusion: one is based on the principle of constant temperature difference. The other is based on the principle of constant power.

Thermal Mass Flow Meter

Based on a common data model:

P / ▷ T = A + B (Q) N.

Among them:

P—dissipated power,

▷T—the temperature difference between the two sensors,

Q—mass flow,

N—exponential coefficient,

A, B is the coefficient related to the thermal performance of the gas.

The principle of constant temperature difference:

▷T remains unchanged, and the dissipated power P and the flow rate Q of the fluid are exponentially increasing.

Constant power principle:

The dissipated power is constant, and the temperature difference ▷T is in a decreasing relationship with the flow rate Q of the fluid.

Know more about How Thermal Mass Flow Meter Technology Works?

Video source:

Thermal meters require a fully developed flow profile as a prerequisite for correct flow measurement. For this reason, please note the following points when installing the device.

  • Observe the recommended inlet and outlet requirements.
  • Good engineering practice is necessary for the associated pipe work and installation.
  • Ensure correct alignment and orientation of the sensor.
  • Take measures to reduce or avoid condensation (e.g. install a condensation trap, thermal insulation, etc.).
  • The maximum permitted ambient temperatures and the medium temperature range must be observed.
  • Install the transmitter in a shaded location or use a protective sun shield.
  • For mechanical reasons, and in order to protect the pipe, it is advisable to support heavy sensors.
  • No installation in where large vibration exists.
  • No exposure in the environment containing a lot of corrosive gas.
  • No sharing power supply with frequency converter, electric welding machine and other machines which can make power-line interference. If necessary, please add power conditioner for transmitter power supply

The minimum recommendations for inlet and outlet runs (without flow conditioner) are:

Flanged sensor

Thermal mass flow meter straight run requirement  Flanged sensor

1 = Reduction, 2 = Expansion, 3 = 90° elbow or T-piece, 4 = 2 × 90° elbow, 5 = 2 × 90° elbow (3-dimensional), 6 = Control valve.

Insertion sensor

Thermal mass flow meter straight run requirement  Insertion sensor

1 = Reduction, 2 = Expansion, 3 = 90° elbow or T-piece, 4 = 2 × 90° elbow, 5 = 2 × 90° elbow (3-dimensional), 6 = Control valve or pressure regulator.

A specially designed perforated plate flow conditioner can be installed if it is not possible to observe the inlet runs required.

Extended reading: Gas mass flow controller working principle

Thermal mass flow meter and Coriolis flow meter are both flow meters used to measure fluid mass flow rate.

The thermal type can only be used in gases. It uses the different heat conduction and absorption capabilities of various gases to measure the heat transfer or heat energy loss from heating to induction to correspond to the flow rate.

Thermal Mass Flowmeters (Thermal Mass Flowmeters, TMF for short) are used to measure thermal flow meters in China. The fluid mass flow is measured by the temperature field change generated when the fluid flows through the pipe heated by the external heat source. Or a flow meter that uses the relationship between the energy required to increase the temperature of the fluid and the mass of the fluid when the fluid is heated to a certain value to measure the mass flow of the fluid. Generally used to measure the mass flow of gas.

Thermal Mass Flowmeters have the characteristics of low pressure loss; large flow range; high precision, high repeatability and high reliability; no moving parts and can be used for extremely low gas flow monitoring and control. Utilizes the heat (or temperature) of the heated fluid Changing the mass flow of fluids has a long history.

Read more about: Applications Of Digital Gas Mass Flow Meters

The usual mass flowmeter refers to Coriolis flowmeter. Use the Coriolis principle (the interference of the earth’s rotation on the curved material) to directly measure the mass of fluid flowing through. Can measure gas and liquid.

The volume of a fluid is a function of fluid temperature and pressure and is a dependent variable. The quality of a fluid is a quantity that does not change with time, space temperature, and pressure.

As mentioned earlier, the flow measurement values ​​of commonly used flow meters, such as orifice flow meters, turbine flow meters, vortex flow meters, electromagnetic flow meters, rotameters, ultrasonic flow meters, and oval gear flow meters, are fluid. Volume flow.

Extended reading: Fuel Flow Meter for Boat-Selection & Application

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Sino-Inst offer over 10 Thermal Mass Flow Meters, with Best Price.

A wide variety of Thermal Mass Flow Meters options are available to you, such as free samples, paid samples. All of our flow meters can work with the AMS NEW TREX. About 13% of these are magnetic flow meter. 14% are Insertion Magnetic Flow Meter. 25% are Venturi flow meter. 13% are Handheld ultrasonic flow meter, and others are Liquid Turbine Flow Meters.

Sino-Inst is Thermal Mass Flow Meter suppliers, located in China. Mass flow meter products are most popular in North America, Mid East, and Eastern Europe.

The United States, and India, which export 99%, 1%, and 1% of Thermal Mass Flow Meter respectively.

You can ensure product safety by selecting from a certified supplier, with ISO9001, ISO14001 certification.

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