Hall Effect Water Flow Sensor YF-S201 
Its model number is YF-S201. 
This sensor is a Hall Effect sensor. 
Its working voltages are 5 to 18V DC. 
Its minimum working voltage is 4.5V DC. 
Its maximum current draw is 15mA @5V. 
Its output type is TTL of 5V. 
Its working flow rate is 1 to 30 liters per minute. 
Its working temperature range is -25 to 80 degrees centigrade. 
The humidity range of the sensor is 35% to 80?gree centigrade. 
Its accuracy percentage is +- 10%. 
2.0 MPa is its maximum water pressure. 
Its output duty cycle is 50% +- 10%. 
0.04 us is its output rise time. 
0.18us is its output fall time. 
We can find flow rate pulse characteristics by this formula: frequency (Hz) = 7.5 * flow rate (L/min) 
450 is approximately pulses per liter. 
Hall Effect Water Flow Sensor YF-S201 minimum cycles are 300,000. 
Its size is approximately is 2.5 x 1.4 x 1.4”.