Thermal Mass Flow Meter

Thermal mass flow meters heat a small sensor and measure how much energy the flowing gas carries away. The reading is mass flow directly, with no temperature or pressure compensation needed. For compressed air and plant gas accounting, that simplicity is the whole argument.

Where the family fits

Compressed air is the classic application. Most plants have no idea what their compressors actually deliver, and compressed air is one of the most expensive utilities per unit of energy. A thermal mass meter on the main header usually pays for itself through leak detection alone.

Other good fits: natural gas at burner level, biogas, flue gas, and any clean dry gas where you care about mass rather than volume.

What decides the model

Pipe size and insertion style first. Small lines use an inline flanged body. Large ducts and headers use an insertion probe, which costs far less than a full-bore meter at DN300 and above.

Then the gas composition. Thermal meters are calibrated for a specific gas or gas mix. If the composition shifts, the calibration drifts with it. For natural gas with varying quality, that matters.

Then turndown. Thermal meters have excellent turndown, often 100:1, which is why they suit compressed air systems that swing from near zero at night to full rate in the day.

Where they are the wrong answer

Wet or dirty gas, condensing vapours, and anything that will coat the sensor. A thermal sensor coated in oil mist reads low and drifts, and there is no alarm to tell you. For dirty gas, a vortex or orifice meter is more robust.

If you are still deciding between technologies, our flow meter selection guide walks through the decision in order.