The Comprehensive Flowmeters Resource

Thermal Mass Flow meter

How do Thermal Mass Flow Sensors work?

This is a basic explanation on some of the most common types of Thermal Mass sensors. There are of course, other variations which may add a twist to the concept and the measurement. These devices are popular for measuring air and gas flow, but some manufacturers have designed the sensors to also work with liquids.

Thermal Probes can be installed in existing pipework at the site location by screwed and flanged connections to measure the ΔT.

Engineers and Technicians recognize this as a measurement of a differential. In this case it is the difference between the actual temperature being measured (by a PT 100) and the constant temperature of the heated sensor.

Probably the best way to start is to visualize what is inside the insert probe. Here we have a heated sensor and a non-heated sensor. These can both be encapsulated to look like it is one rod, but it is important to remember there are always two sensors or two measuring points.  The heated sensor is designed to always be at a constant temperature while the unheated sensor is actually measuring the temperature inside the pipe or conduit.

When the flow increases, the heated sensor will begin to cool. In order for the heated sensor to maintain it’s steady temperature, more energy will be needed to heat it up.  The amount of energy required for the heated sensor to maintain it’s constant temperature is directly proportional to the flow velocity e.g. feet per second or meters per second.

In a pipe or a conduit, flow velocity can be used to calculate the volumetric flow if the diameter of the pipe/conduit is known. An over simplified calculation (without corrections for Reynolds numbers) can be understood by spending time with a flow velocity to volume calculation e.g. 

Pipe Flow Calculator

What else?

Full Bore Flow Through Types

Natural Gas Flow Switch


  • Compressed air flow monitoring
  • Boilers – natural gas power
  • Monitoring Hydrogen flow
  • Gas Mixers – additive injection
  • Testing for leaks in valves
  • Kiln applications
  • Purge Gas and Air
  • Biogas Monitoring
  • Test Separator Gas Outlet leg
  • Oxygen Flows
  • Air Dryers – flow rate
  • Flare gas stack velocity monitoring
  • Flow rate of nitrogen blanketing for tanks
  • Propane pipeline flow
  • Argon Applications
  • N2 nitrogen flow rates
  • Aluminum smelter chlorine flow
  • Compressed air
  • Power Plants Gas and Air flows
  • Combustion process air flow
  • Genset gas flow rate
  • Coal mining heated air flow
  • Contaminant unit vent air flow
  • Digester gas projects requiring gas flow
  • Carbon-Dioxide in beer manufacturing
  • Air vent systems
  • Compressor air flow
  • Natural gas consumption
  • Powder plant air flow
  • Paint booth/paint oven ventilation
  • Engine test stands air flow measurement
  • Fuel cell hydrogen flow
  • Natural Gas Transmission
  • Natural gas to compressor stations
  • Natural gas to gas-fired compressors
  • Landfill gas GHG emissions reporting and Dump Gas

Common Gases

  •  Air
  • Ammonia
  • Biogas
  • Butane
  • Hexane
  • Chlorine
  • Compressed air
  • Carbon monoxide
  • Carbon dioxide
  • Digester gas
  • Dump gas
  • Ethane
  • Helium
  • Hydrogen
  • Methane
  • Natural gas
  • Nitrogen
  • Oxygen
  • Propane

Made in USA

Insertion Type

We can configure a flow meter to fit into an existing pipeline.

Affordable solutions for larger pipes. Measure gas with ease!

Call: +1 (318) 614-3971

4600 FM-307 Midland, TX 79706 United States


Our facilities are located in Rayville Louisiana where we provide liquid and gas flow solutions for our customers in the US.

We make it easier because you can purchase or rent a flow meter.

For our other liquid flow meter solutions visit this website:

Scroll to Top