Dwyer Instruments TDFS2-1-P-06Product Attribute Attribute Value Alternate Mfr Part Number TDFS 1 P 06 Overview The Series TDFS is a thermal flow switch that indicates whether the flow rate is above or below a user set flow rate with NO and NC NPN outputs. Setpoint is easily field set, just tap the included magnet on the setpoint target three times at the desired flow rate and it? s done. Incorporated into the unit are two LED status indicators on opposite sides of the unit