Simple Digital Water Flow Meter Circuit using

Simple Digital Water Flow Meter Circuit using
We will be taking a look at water flow sensor, its construction and working and how to interface with Arduino to extract some useful readings.

The proposed project can measure the rate of water flow in litre / minute and total water flow in litres.

Let’s take a look at this water flow sensor.

It is a Hall Effect based water sensor. It has three terminals 5V (nominal working voltage), GND and output. The +5V is red coloured wire, the black one is GND and yellow one is output.

The sensor gives out frequency directly proportional to water flow. The sensor can measure from 1 litre / minute to 30 litre / minute. The water pressure should be less than or equal to 1.75 MPa.

The water can be injected from one end and water flows through the other end.

The sensor may be placed after the main gate-valve of tank; if you want to measure the water flow in a network of water pipes or you can place just before a water tap to measure the water flow of single tap.

The placement of the sensor can be anywhere according to user’s need but, care must be taken to avoid leakage of water.

The sensor has a magnet and Hall Effect sensor; if we take a look at the sides of the water flow sensor, we can witness a plastic turbine in the path of water flow.

A round shaped magnet is embedded at the center of the turbine and the Hall Effect sensor is sealed and protected from moisture and placed above the magnet. The Hall Effect sensor produces a pulse for every revolution of the turbine.

Water Flow Waveform on Serial Plotter
We can see the pulses generated by water flow sensor on serial plotter.

We have blown air through the sensor to rotate the turbine as a test and the waveform generated is shown above. The denser waveform on left hand side represents higher frequency and faster rotation of turbine, the less dense waveform at right hand side signifies the vice versa.

A consistent water flow gives out consistent frequency output.

We have to convert the frequency into litre/minute scale. To do this, the manufacturer has given a formula:

Water flow rate (litre/min) = frequency / 7.5
So, we need to measure the generated frequency and apply the above formula in the program code.


JOYO M&C was awarded by Sinopec annual technology innovation awards for its invitational technology for its product and solutions of tank and terminal automation, by which operation is greatly faciliated and efficiency is greatly improved for customers.


Mass or Volumetric Flow Rate

So you want to measure flow? The answer would seem to be to purchase a flowmeter. With fluid flow defined as the amount of fluid that travels past a given location, this would seem to be straightforward — any flowmeter would suffice. However, consider the The following equation describing the flow of a fluid in a pipe.

Q = A x v

Q is flow rate, A is the crosssectional area of ​​the pipe, and v is the average fluid velocity in the pipe. Putting this equation into action, the flow of a fluid traveling at an average velocity of a 1 meter per second through a pipe with a 1 square meter cross-sectional area is 1 cubic meter per second. Note that Q is a volume per unit time, so Q is commonly denoted as the “volumetric” flow rate. Now consider the following equation:

W = rho x Q

Where W is flow rate (again-read on), and rho is the fluid density. Putting this equation into action, the flow rate will be 1 kilogram per second when 1 cubic meter per second of a fluid with a density of 1 kilogram per cubic meter is flowing. (The same can be done for the commonly-used “pounds”. Without getting into details — a pound is assumed to be a mass unit.) Note that W is a mass per unit time, so W is commonly denoted as the “mass” flow rate. Now — which flow do you want to measure? Not sure? In some applications, measuring the volumetric flow is the thing to do.

Consider filling a tank. Volumetric flow may be of interest to avoid overflowing a tank where liquids of differing densities can be added. (Then again, a level transmitter and high level switch / shutoff may obviate the need for a flowmeter.) Consider controlling fluid flow into a process that can only accept a limited volume per unit time. Volumetric flow measurement would seem applicable.

In other processes, mass flow is important. Consider chemical reactions where it is desirable to react substances A, B and C. Of interest is the number of molecules present (its mass), not its volume. Similar, when buying and selling products ( custody transfer) the mass is important, not its volume.
How much maintenance does a flowmeter require?
A number of factors influence maintenance requirements and the life expectancy of flowmeters. The major factor, of course, is matching the right instrument to the particular application. Poorly selected devices invariably will cause problems at an early date. Flowmeters with no moving parts usually will require less attention than units with moving parts. But all flowmeters eventually require some kind of maintenance.


Flow meters of Fluid and flow characteristics

The fluid and its given and its pressure, temperature, allowable pressure drop, density (or specific gravity), conductivity, viscosity (Newtonian or not?) and vapor pressure at maximum operating temperature are listed, together with an indication of how these properties might vary or interact. In addition, all safety or toxicity information should be provided, together with detailed data on the fluid’s composition, presence of bubbles, solids (abrasive or soft, size of particles, fibers), tendency to coat, and light transmission qualities (opaque, translucent or transparent?).
Pressure & Temperature Ranges
Expected minimum and maximum pressure and temperature values should be given in addition to the normal operating values when selecting flowmeters. Whether flow can reverse, whether it does not always fill the pipe, whether slug flow can develop (air-solids-liquid), whether aeration or pulsation is likely, whether sudden temperature changes can occur, or whether special precautions are needed during cleaning and maintenance, these facts, too, should be stated.

Piping and Installation Area
Concerning the piping and the area where the flowmeters are to be located, consider: For the piping, its direction (avoid downward flow in liquid applications), size, material, schedule, flange-pressure rating, accessibility, up or downstream turns, valves, regulators, and available straight-pipe run lengths. The specifying engineer must know if vibration or magnetic fields are present or possible in the area, if electric or pneumatic power is available, if the area is classified for explosion hazards, or if there are other special requirements such as compliance with sanitary or clean-in-place (CIP) regulations.


Based on 20 years experiences in the industry, JOYO M&C developed many products with invitational and patented technologies, most products and solutions are proven to be  with high competence in terms of functions and performances. JOYO M&C was awarded by Sinopec annual technology innovation awards for its invitational technology for its product and solutions of tank and terminal automation, by which operation is greatly faciliated and efficiency is greatly improved for customers.