Flow transducers

Recent advances in flow detection have resulted in more accurate, durable and cost-effective meters. It is becoming increasingly important to be able to connect flow meters to a computer for instant flow readings, remote flow control or to enable unattended process operation.

To meet these demands, new types of flow transducers are being introduced and older designs are being improved and upgraded.

The primary factors to consider when selecting a flow transducer are:

• type of medium e.g. water, air;
• medium flow velocity range;
• medium temperature and pressure;
• accuracy;
• measuring range;
• output value type e.g. voltage, current;
• ease of installation and maintenance requirements.

Let's take a closer look at the principle of such transducers and what types we can find in the industrial sector.

Working principle of flow transducers

Flowmeters are used to measure the velocity of air or liquid flow. Flow meter sensors work in different ways, but have the same end goal: to provide the most accurate and repeatable flow measurement for a specific application, whether for process control, general scientific research or semiconductor processing.

The most common solutions can calculate the flow level or its quantity based on the cross-sectional area of the pipe. Then, the analytical components of the transducers convert this value into an appropriate output signal.

You can find transducers based on Faraday's law of induction. A medium flows through a pipe in a certain magnetic field, producing a voltage proportional to the amount of that medium or its velocity.

Another type are transducers, which through the flowing medium, count the resulting turbulence depending on the speed of the medium. If we know the cross-section of the pipe, we can determine the flow rate.

Other solutions use ultrasound reflections and measure the transit time of the signals between the ultrasound transducers. By calculating the time difference between the reflections received by the transducers, the flow rate can be determined and converted to an output value accordingly.

There are also sensors with spring-loaded pistons. Through the flowing medium, a piston located in a valve of the transducer housing exerts pressure on a spring. The position of the spring is monitored by special sensors, usually magnetic, which send the corresponding analogue signals to the evaluation units.

Applications for flow transducers in industry

Flow transducers are used in almost all areas of process and engineering where liquids or gases are used, e.g. to provide equipment and machinery with coolant and lubricants, in hall and building ventilation systems, in processing etc. If the flow is not correct, significant damage and downtime in the industry can result. Inaccurate flow measurements or failure to measure can cause serious and irreversible consequences. In modern installations, electronic monitoring systems are used to prevent such situations. Below are some of the many applications of flow sensors:

• controlling irrigation and water consumption in the agricultural industry;
• maintaining energy efficiency and usability of HVAC systems;
• wastewater treatment facilities;
• monitoring product flow in the food, pharmaceutical and other industries;
• monitoring pump operation, balancing system flow;
• diesel and other oil flow monitoring, cooling water flow in power industry;
• monitoring of water, fuel and lubricant consumption and related products in the form of sludge and slurry in the mining industry.

Choosing the right solution for your industrial process

Choosing the best flow transducer for industrial systems is not as complicated as it sounds. The most important variables in this choice are pipe size and the type of fluid used in the cooling system. There are many flow monitoring technologies, such as the models described in this article and each type of device can be purchased for different pipe sizes.

For a basic water-cooling system, a simple impeller flowmeter is usually sufficient. These are economical and easy to install in almost any system, and they are compatible with many types of pipe. The unit is simply installed so that the impeller is in line with the direction of water flow. Many impeller-type meters are available with temperature probes that plug directly into the meter to calculate overall efficiency.

Ultrasonic meters are useful in applications where liquids other than water are present, as some chemicals can damage impellers. Ultrasonic meters can also measure flow in both directions.

Electromagnetic flowmeters measure flow in conductive fluids. Electromagnetic flow meters are useful for slurries and other liquids containing solids that could contaminate the impeller or interfere with the ultrasonic transducer.

In summary, improving the efficiency of industrial systems has a direct impact on a facility's bottom line. Flow monitoring is a critical variable in efficiency calculations. To best manage a facility's energy consumption, more information is always better so invest in durable, high-quality flow measurement equipment.