### Introduction to Electromagnetic Flow Meters

#### What is a magnetic or electromagnetic flow meter?

Also referred to as a “ magmeter” it is a device that measures the volumetric flow of liquids in a pipe (e.g gallons per hour, liters per minute) on a continual basis and is a well known piece of equipment in water and wastewater industries.

#### What is the principle of operation

The electromagnetic equipment works by creating a magnetic field (normally by coils that are positioned at opposing sides of a pipe)

In order for this measurement technique to work, the liquid needs to be conductive.

The induced voltage will vary depending on the velocity of the liquid.

For a more detailed explanation on just how this is achieved, the following video presentation has been developed by SG Flowmeters Pte Ltd .

In this technical magnetic flow meter video presentation, it becomes easier to grasp and to visualize the working concept and the reason for the implementation of the coils and electrodes.

#### Electromagnetic Flow Meters (Video Transcript)

Magnetic flow meters are devices that utilize a magnetic field to measure the velocity of a fluid, normally in a pipe. This velocity can be converted to a volumetric flow rate such as liters per minute or gallons per hour. How do magnetic flow meters work? Firstly, a magnetic field is created by coils on opposing sides. Normally these coils are made of copper. A conductive fluid passes through the magnetic field and the induced voltage will vary depending on the velocity of the liquid. Voltage is generated by the fluid flowing through the magnetic field. The faster the fluid flows, the more voltage is generated through the electrodes . The voltage is measured by the electrodes . This shows one of Faraday’s laws in operation. The volumetric flow rate can be calculated by using the equation Q= Av. Calibration of Magnetic flow meters at the factory to a high standard and Reynolds compensation improves accuracy and repeatability. Volumetric flow rates can be displayed in both metric , imperial and SI units e.g Meters cubed per hour, gallons per minute etc. Outputs for magnetic flow meters can be 4-20mA, pulse, modbus and other protocols for remote transmission of a reading. Magnetic flow meters are very popular in measuring the flow of raw water, tap water, drinking water, sewage water and wastewater. The magmeters are often seen in all types of manufacturing plants that measure inlet, outlet and process water consumption. Since magmeters have no moving parts, they can be manufactured as full bore, full flow through measuring devices. Magnetic flow meters are able to measure flow bi-directionally This presentation was brought to you by SG Flowmeters Private Ltd.

#### What is a battery powered magnetic flow meter?

As the name suggests, it is a flow meter that runs on batteries. This means the meter does not need an external power source.

#### What are the most common applications for battery powered flow meters?

Very often, an organization might come across a situation where there is no power available due to long distances from electrical substations which means it is very difficult to tap power from the grid unless extremely long cables are implemented. Without a reliable power source, the option is to buy and install a flow meter than runs on battery power.

There are many types of battery-operated flowmeters. Some are used as portable flow meters while other are permanently installed in a flow line. In Singapore, we have supplied battery operated solutions for turbine flow meters,  battery powered electromagnetic flow meters and ultrasonic flowmeters.  One of the main differences in the design often has to do with the electronics. To ensure a longer working life for the battery it is often required that the electronic circuits are a low power consumption type. Where this is not possible, it is recommended to minimize the data retrieval. For example, if a flow meter is reporting the flow rate to an external device every 500 ms, then the battery life is compromised due to the larger energy consumption. This issue can be mitigated by setting the output, data logging or data output to a more reasonable time interval e.g. one a day.

#### What are some the advantages of using a battery-operated electromagnetic flow meter equipment?

1. Lower capital expenditure
2. Minimized wiring or no wiring at all
3. Ability to measure flows in remote areas
4. Ability to measure flows in difficult to access areas
5. Installation requirements minimized
6. Flexibility, especially if it needs to be relocated to another project.

Another huge advantage of a battery-operated flowmeter is the ability to obtain flow data very quickly. In some cases, the user may even opt to measure the flow rate using a locally available ultrasonic flow meter  which has virtually no installation requirements except for the clamping of flow sensors to the outside of wall of a pipe.

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