Intro to Flowmeters - Part 3

In the previous sections we have looked at what flowmeters are, why they are important to us and we have explored mechanical as well as differential pressure flowmeters. The two types of flowmeters we have looked at had the disadvantage of downstream pressure drops and moving parts that are subject to wear and will break down over time. The flowmeters in this section have significantly less of a pressure drop or no pressure drop at all.

There are many types of electronic flowmeters, each with its own use and set of advantages/disadvantages. The main types of electronic flowmeters are the vortex flowmeter, magnetic flowmeter and ultrasonic flowmeter.

A magnetic flowmeter works with fluids that are conductive. In this type of device a fluid is passed through a flow tube. This tube is non-magnetic and has an insulated lining with electrodes inserted at each end. It is important to remove air or other gas bubbles from the flow prior to it reaching the flowmeter. Liquids that can collect on the walls of your conduit can cause a constriction that will affect the accuracy of your measurements.

Vortex flowmeters have been around since the early part of the 1970s and are used a lot as a alternative to differential pressure flowmeters. Vortex flowmeters have less effect on the downstream pressure, they are economical, easy to set up and have become popular across many industries. You will not want to use this type of flowmeter where there can be a buildup of "sludge" in the pipes lining or the meter itself.

Ultrasonic flowmeters measure the transit time or frequency shift of ultrasonic waves in an acoustic field. These come in both inline versions where they are installed as a permanent part of the system and also come in clamp on versions that can be moved from location to location. The portable version of the vortex flowmeter has no effect on the downstream pressure. One of the attractions of this type of flowmeter is the low maintenance cost and they last longer but they may have higher installation cost for the inline models.

There is another type of flowmeter and that is the mass flowmeter. They measure fluids or gases in units of mass flow such as pounds per minute. The most used types of these are the thermal flowmeter and coriolis flowmeters. Both of these devices are considered very accurate and have a very wide range of applications but may be more costly to set up.

This article is intended as a basic introduction to flowmeters. This three part article is not meant to teach you all you need to know about flowmeters but rather to help you understand the basic types and uses of them. Our site and other sites on the web contain much more detailed information. Some of these other sites are linked to buy banners and also in our links section.