Many applications need a precise
measurement of water flows both for drinking water, irrigation, and removal of
dirty water, RO water, condensate water, sewage water or water use in
industrial processes. An accurate measure of the amount of water used comes
from the water flow meter.
We list basic types of digital flow meters for measuring water:Each type works differently with advantages and disadvantages.
Below we explain some Knowledge of flow meter:
The accuracy of an electronic water flow meter shows as a percentage showing how the volume of water measured by a flow meter compares to the exact volume. A low percentage indicates an accurate measurement of volumetric flow.
The repeatability of a digital flow meter is the ability to precisely measure the same volume of water under the same conditions of temperature, pressure, and flow. Excellent repeatability indicates quality measurement over a range of different conditions.
The output from the digital water flow meter could be 4-20mA analog output, pulse or frequency output, the digital communication could be HART,RS485 or Profibus-DP.
Electromagnetic flowmeter is a flowmeter that measures flow according to Faraday's law of electromagnetic induction. The advantage of the electromagnetic flowmeter is that the pressure loss is extremely small, and the measurable flow range is large. The ratio of the maximum flow to the minimum flow is generally more than 20: 1.The applicable industrial pipe diameter range is wide, up to 3m, the output signal and the measured flow are linear, the accuracy is high, and the conductivity can be measured ≥5μs / cm Acid, alkali, salt solution, water, sewage, corrosive liquid and fluid flow of mud, pulp, pulp, etc，or used as industrial water meter, But it cannot measure the flow of gas, steam and pure water.
Digtal Magnetic water flow meter standard with pulse
& 4-20mA current output, option with
RS485,HART or profibus-DP.
The turbine flow meter works mechanically by allowing the water flowing through the pipe to rotate a free-spinning turbine. The velocity (speed) of the blade rotation is directly related to the velocity of the water flowing through the turbine flow meter. The output signal (frequency of rotation) is fed through a second device to provide a reading as flow rate, volume and other variables.
A turbine flow meter is straightforward to install and needs minimal maintenance – occasional recalibration and servicing.
Turbine flow meters work efficiently in clean water ,so it can be used as RO water flow meter, chilled water flow meter, tap water flow meter or drinking water or water from well. Turbine flow meters are sensitive to particles in the water and changes in viscosity. The turndown range is 10:1 at best, and they are not the best flow meter in low flow conditions.
The output from digital turbine water flow meter
can be current output or pulse output.
When water flows past an obstruction (like a rock in a stream) eddies form. These miniature whirlpools are vortices. Different types of sensors measure the frequency of the vortices created by a shedder bar. The volumetric flow rate is directly proportional to the vortices frequency.
The vortex flow meter has excellent repeatability (0.15%) and has no moving parts resulting in minimal maintenance. It is not suitable for low flow rates, and it needs to be in the middle of a straight pipe run (minimum length). Installation is straightforward and it is consistently accurate in a range of conditions.
Electronic vortex flow transmitters with digital
display to show water instant flow and total flow, it is with output , such as
frequency , pulse or 4-20mA.
Water moves through a tube or tubes. The tube vibrates and the flow of water through the vibrating tube(s) causes a twist in the tube. The twist is proportional to the mass flow down the pipe – measure the twist – calculate the mass flow. The mass flow rate can easily convert into a volumetric flow rate.
The Coriolis flow meter’s accuracy is unaffected by the amount of flow or fluid density. They have excellent repeatability (0.1%) and turndown of 20:1.
Compared with the turbine and vortex flow meters, they are high cost, but they are low maintenance and easy to install. A Coriolis flow meter is sensitive to noise and vibrations, which can cause measurement errors, but additional equipment (extra cost) filters this noise out from the readings.
Coriolis flow meter is to measure water mass
flow, output frequency, pulse or 4-20mA.
A rotameter measures the rising of a float in a tapered tube. The tube is made from glass, metal, or plastic and is mounted vertically so the water comes through the narrow end and exits through the wide end.
The principle is simple – the water pushes the float up a widening tube until the float reaches a stable position when the waters upward force balances the float’s weight. A table shows the float position compared with water flow.
A rotameter is a variable area meter and is several hundred years old. They don’t require power to operate, they are low cost, and the process is repeatable and easy to understand by observation. They are straightforward to install and require minimal maintenance. They operate from low to high flow rates with excellent accuracy.
Silver Automation Instruments offer metal tube rotameter with transmitters ,it can output 4-20mA or pulse.