... low pressure loss 4, Easy installation Electronic flow sensor (Thermal differential type)Principle Based on the ... of thermal theory, there are two resistances in the closed probe . One resistance was heated ... differential resistances value is the basis of determining the flow velocity . Feature1,No movable parts . 2, Maintenance ... ( water),3…300cm/s(oil),20…2000cm/s(air)Output: PNP, NPN, Relay ,4-20mA, ...