Turck flow switch is designed based on the principle of temperature change of probe head. In the probe built-in heat sensor and heat sensor, and contact with the medium. When measuring, the heat sensor sends out constant heat, when there is no medium flow in the pipeline, the heat received by the heat sensor is a constant value, when there is a medium flow, the heat received by the heat sensor will change with the flow rate of the medium, the heat sensor will convert the temperature difference signal into electrical signal, and then through the circuit converted to the corresponding contact signal or analog signal. FCI-D03A4-NA-H1141/M12