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A thermal gas mass flow meter is based on the principle of thermal diffusion; that is, when a fluid flows past a heating element, the amount of heat lost by that element is proportional to the flow rate of the fluid. Specifically, the sensor of such a flow meter consists of two standard RTDs – one used as the heat source and the other used to measure the temperature of the fluid. As the fluid passes by, the heat loss from the heat source is linearly related to the flow rate, and the thermal gas mass flow meter can convert this relationship into a linear output signal representing the flow rate. There are two design approaches for flowmeters manufactured using the principle of heat diffusion, both based on a common model: P/ΔT = D + Eqkm, where P represents the dissipation power, ΔT is the temperature difference between the two sensors, D is a constant related to the actual flow, E is a constant related to the thermal properties of the gas being measured, qm is the mass flow rate, and K is an exponential coefficient. In thermal mass flowmeters, the temperature sensors (RTDs) are placed in two metal tubes within the gas stream; one thermistor measures the temperature of the gas stream, T, while the other tube is heated by an electric heater with a constant power level, resulting in a temperature Tv that is higher than that of the gas stream. When the gas is at rest, Tv is at its highest value; as the mass flow rate increases, more heat is carried away by the gas stream, causing the temperature to drop. The temperature difference ΔT is then calculated as ΔT = Tv – T. This method is known as the “temperature difference measurement method” or “temperature measurement approach”. For more information, please visit the company’s official website at http://www.yb1518.com/. Please retain this link when reproducing the content! http://www.yb1518.com/UploadFiles/201511391437413.jpg