Water Flow Sensor YF-S401


This simple flow sensor is very similar to its big brother, the YF-S201, but has been optimized for lower flow rates and features a higher pulse per liter count. Inside the housing, a small pinwheel with an attached magnet is spun by passing water; as the magnet makes each revolution, a hall effect sensor inside the housing outputs a pulse on the yellow wire.

This sensor is best suited for flow rates between 0.3 and 6 liters per minute and outputs 5880 pulses per liter (approximately 1 pulse per 0.17mL). The sensor has a barbed 7mm connection point on each side with an inner diameter of 4mm.

  • A 6 mm hose is recommended
  • Avoid unit contact with corrosive chemicals
  • The unit must be installed vertically, tilted no more than 5 degrees
  • Liquid temperature should be less than 120 C to avoid damage to unit


  • Model: YS-S401
  • Working Voltage: DC 5V~12V
  • Maximum Working Current: 15mA @ 5V DC
  • Flow Rate Range: 0.3~6L/min
  • Inlet Water Pipe Diameter: 4mm
  • Load Capacity: ≤10mA (DC 5V)
  • Water Pressure: ≤0.8MPa



  • Red: Power In
  • Black: Ground
  • Yellow: Signal Output


  • Water heaters
  • Water vending machine
  • Flow measurement device
  • Automatic water dispenser
  • Agriculture
  • Food processing
  • Coffee/Tea makers
  • Water Management

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