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How Does a Thermal Mass Flow Meter Work

Featured Product from Eldridge Products, Inc.

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Thermal mass flow meters detect mass flow directly using the convective heat transfer theory. Two ratiometrically matched, reference-grade platinum Resistance Temperature Detectors (RTDs) are used in EPI's unique thermal mass flow sensors. The platinum sensing element wire is encased in a 316 Stainless Steel sheath or a Hastelloy C sheath if one is required. Our intelligent sensor technology, which is controlled by a microprocessor, preferentially warms one RTD. At the same time, the other serves as a temperature reference. The heat from the first RTD is dissipated by the process gas flow, increasing the power necessary to keep an equilibrium between the RTDs. This rise is proportional to the molecular rate of flow of the gas. Our sensors are temperature adjusted for a wide range of process gas temperatures. As a result, they are unaffected by pressure fluctuations, resulting in a real mass flow rate indication of the output signal.