Water Flow Sensor Working and Applications

Water Flow

Water flow sensors are installed at the water source or pipes to measure the rate of flow of water and calculate the amount of water flowed through the pipe. Rate of flow of water is measured as liters per hour or cubic meters.
Water flow sensor consists of a copper body, a water rotor, and a hall-effect sensor. When water flows through the rotor, rotor rolls, its speed changes with different rate of flow.


Flow is defined as the quantity of fluid (gas, liquid, vapour or sublimate) that passes a point per unit time
It can be presented by a simple equation: Flow (Q) = quantity/time
It is the rate of change of a quantity. It is either volumetric or mass flow rate.

Properties Affecting Fluid Flow

Velocity of Fluid – the fluid speed in the direction of flow. The fluid velocity depends on the head pressure that is forcing the fluid through the pipe. The greater head pressure, the faster fluid will flow.
Pipe size – the larger the pipe, the greater the potential flow rate
Pipe friction – reduces the flow rate through the pipe. Flow rate of the fluid is slower near walls of the pipe that at the center.
Fluid viscosity – its physical resistance to flow.
The specific gravity of fluid – at any given operating condition, the higher fluid’s specific gravity, the lower its flow rate.
Fluid condition – the condition of fluid (clear or dirty) is one of the limitations in flow measurement, some measuring devices blocked/plugged or eroded if dirty fluids are used.
Velocity Profiles – it has major effect on the accuracy of most flow meters. It can be laminar, transitional or turbulent flow. Properties Affecting Fluid Flow

Importance of Fluid Measurement

Measuring flow is one of the most important aspects of process control
The most diverse substances are transported and distributed in piping system
The fluid flowing through pipes have different properties, so different flow measuring devices are used
The maintenance of definite rates of flow is important for maximum efficiency and production

What is Water Flow Sensor?

Huge industrial plants, commercial and residential buildings require a large amount of water supply. The public water supply system is used to meet this requirement. To monitor the amount of water being supplied and used, the rate of flow of water has to be measured. Water flow sensors are used for this purpose.
Water flow sensors are installed at the water source or pipes to measure the rate of flow of water and calculate the amount of water flowed through the pipe.

Differential pressure flow meters

  • Coriolis Flow meter
  • Vortex Flow meter
  • Ultrasonic Flow meter
  • Electromagnetic Flow meter
  • Thermal Flow meter

Working Principle

Water flow sensor consists of a plastic valve from which water can pass. A water rotor along with a hall effect sensor is present the sense and measure the water flow.
When water flows through the valve it rotates the rotor. By this, the change can be observed in the speed of the motor. This change is calculated as output as a pulse signal by the hall effect sensor. Thus, the rate of flow of water can be measured.
The main working principle behind the working of this sensor is the Hall effect. According to this principle, in this sensor, a voltage difference is induced in the conductor due to the rotation of the rotor. This induced voltage difference is transverse to the electric current.

When the moving fan is rotated due to the flow of water, it rotates the rotor which induces the voltage. This induced voltage is measured by the hall effect sensor and displayed on the LCD display.
The water flow sensor can be used with hot waters, cold waters, warm waters, clean water, and dirty water also. These sensors are available in different diameters, with different flow rate ranges.
These sensors can be easily interfaced with microcontrollers like Arduino. For this, an Arduino microcontroller board for processing, a Hall effect water flow sensor, a 16×2 LCD display, and Breadboard connecting wires are required. The sensor is placed at the water source inlet or at the opening of the pipe.
The sensor contains three wires. Red wire to connect with supply voltage. Black wire to connect to ground and a yellow wire to collect output from Hall effect sensor. For supply voltage 5V to 18V of DC is required.

Compact, Easy to Install
High Sealing Performance
High Quality Hall Effect Sensor
RoHS Compliant

Applications of Water Flow Sensor

  • Water flow sensors can measure the rate of flow of water either by measuring velocity or displacement. These sensors can also measure the flow of water like fluids such as measuring milk in a dairy industry etc…
  • There are various types of water flow sensors available based on their diameter and method of measuring. A cost-effective and most commonly used water flow sensor is Paddlewheel sensor. It can be used with water-like fluids.
  • For the type of applications where a straight pipe is not available for inlet, Positive displacement flow meter is used. This type of water flow sensor can be used for viscous liquids also.
  • For working with dirty water and wastewater which may be conductive, Magnetic flow meter is used. For applications such as sewage water, slurries, and other dirty liquids Ultrasonic flow meters are used.
  • The LCD display is used to display the measurements. The magnetic hall effect water flow sensor outputs a pulse of every revolution of the rotor. The hall effect sensor present in the device is sealed from water to keep it safe and dry.

Example of Water Flow Sensor

YFS201 Hall effect sensor is an example of this sensor. These sensors also require a display to display the measurements. This sensor outputs 4-5 pulses for every liter of liquid flowing through it per minute. It has a working flow rate of 1-30liters per minute. Easy to use and cost-effectiveness are the important characteristics of this sensor.