Why is the flow rate output from a thermal mass flow sensor the nominal flow rate?

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In the field of industrial automation control, flow is one of the very important parameters. As a commonly used flow measurement device, the thermal mass flow sensor's output flow is often expressed in the form of standard flow. So, why is the flow rate output by the thermal mass flow sensor the standard flow rate? The standard flow rate refers to the flow rate under standard conditions, that is, the temperature is 0 degrees Celsius and the pressure is 1 atmosphere. This flow rate is usually considered a standardized flow rate and can be used to compare flow rates in different regions, at different times, and under different working conditions.

The thermal mass flow sensor is a device that uses the principle of heat conduction to measure flow. When fluid flows through the heating element, the heating element is cooled by the fluid, causing the temperature of the heating element to drop. The temperature change of the heating element will directly affect the change of its resistance value, so we can calculate the fluid flow rate by measuring the change of the resistance value of the heating element. In the output of the thermal mass flow sensor, the flow value is usually expressed in the form of standard flow rate. This is because in the field of industrial automation control, standard flow is a universal flow unit that can be used to compare the flow between different equipment and different processes. At the same time, standard traffic is easier to understand and use. Of course, thermal mass flow sensors can also measure the flow of other parameters, such as mass flow, volume flow, etc. However, these parameters require certain conversion calculations, which are not as direct and simple as the standard flow rate.