Termal Mass Industrial
The immersible thermal sensor is completely immersed into the flow stream. As a result, immersible thermal mass flow meters measure much higher gas mass flow rates in harsher environments than capillary thermal mass flow meters. There is very little pressure drop across an immersible sensor, and the flow does not have to pass through the LFE as it does with a capillary thermal mass flow sensor.
In operation, the reference thermistor measures the temperature of the gas, while the flow thermistor is electronically maintained at a temperature typically 40°C degrees hotter than the gas temperature. Once the gas begins to flow, the flow thermistor is cooled as the molecules of gas take heat away from the heated flow thermistor (think of blowing on your wetted finger…it will feel cooler as your breath passes over it). The amount of heat removed from the flow thermistor is added back by the electronic heater circuit so a constant temperature differential ΔT between the two thermistors is maintained. The heat INTO the flow thermistor (measured electronically) is equal to the heat OUT of the sensor that is convected away by the flow stream.