Tackling the Limitations of Thermal Mass Flow Measurement

Like any flow measurement technology, thermal mass flow meters have limits, as well as benefits. Understanding and overcoming the challenges can be quite advantageous, yet users need to know when to seek alternative solutions.

In a recent article, “How to Overcome Thermal Mass Flow Meter Limitations,” Wayne Shannon, the Sage Metering Product Marketing Manager, identifies nine limitations of the technology and offers tips on how to overcome them.

What are the benefits of thermal flow meters?

There are many advantages of using thermal mass flow meters, and they are well-matched for various applications such as emissions monitoring, stack flow measurement, even natural gas flow. However, this technology’s two primary benefits, which measure mass flow, are that the meter is relatively inexpensive versus its alternatives (Coriolis), and they measure low flow (low pressure) where other technologies struggle.

What are the limitations, and how to overcome them?

In this article, Shannon discusses nine limitations of the technology with straightforward answers on working around them. The limits explored are:

1. 1. Condensed moisture in gas (wet gas) decreases the accuracy of the meter.
   2. The thermal mass flow meter has diminished sensitivity at high velocities.
   3. Thermal mass flow meters can only measure the gas (or gas mixture) the manufacturer calibrated the meter.
   4. Thermal mass flow meters must have the calibration verified or sent to a NIST facility for re-calibration regularly.
   5. Any change in a gas composition will decrease the accuracy of the flow meter.
   6. An undeveloped flow profile will reduce the accuracy of a thermal mass flow meter.
   7. Sensor buildup increases the mass, impedes response time, and reduces the accuracy of the meter.
   8. Measuring flow in large ducts is challenging because of the difficulty in creating a developed flow profile.
   9. While thermal mass flow meters excel at measuring low velocity (flow), the manufacturer must calibrate the meter at low flow velocity.

To learn tips on overcoming these nine limitations of thermal mass flow measurement, visit Sage Metering Overcomes Limitations. For a cheat sheet, you may also be interested in The Pros and Cons of Thermal Mass Flow Meters – Q&A.

9 Thermal Mass Flow Meter Advantages

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