Selecting a Pressure Transmitter
With so many choices, selecting a pressure transmitter can be a frustrating endeavor but it doesn’t have to be. With a few simple steps, finding the right transmitter for your application can be considerably easier.
- Understand your application. Examine the particulars of your application. Is it necessary to know if the pressure is negative or positive? Do you need to know the difference in pressure between two points? Answering these questions as well as others about your application will go a long way in helping select the right pressure transmitter. Having the right type of pressure transmitter for your application is essential to get the results you want.
- Pick the best transmitter for the right medium. Selecting the transmitter with wetted parts that are compatible with the medium to be measured helps to ensure a long-lasting measurement solution. Almost any pressure transmitter will last for a short period in the harshest environment. The real challenge comes in selecting the pressure transmitter that will yield the most reasonable lifetime for the project at hand. Steam, refrigerants and other corrosives all require special attention for effective longer-lasting measurement applications.
- More money means better results, right? Economics is also a part of engineering. Selecting the most accurate parts, the longest-lasting parts, and the parts constructed with only the best materials will drive up the price tremendously. Spending a couple of thousand dollars on an extremely high quality transmitter may ensure long-lasting and highly accurate results, but careful analysis may lead you to conclude that a couple off handed dollars will buy you a transmitter that will work just as well.
- Consider the range before you select the transmitter. Picking an accurate device for your particular application is a good start, but picking the wrong range can undo everything you are trying to accomplish. For instance, selecting a pressure transmitter with a range of 0 to 100 psi with an accuracy of +/- 0.5% to be used to measure a pressure that may reach a maximum of 10 psi is probably not a good idea. An accuracy of +/- 0.5% over a 100 psi range means that the maximum error you may see is +/- 0.5 psi. With a reading of 6 psi the actual value may be anywhere from 5.5 to 6.5 psi. An error of 0.5 psi means your device has inaccuracy of 8.3% at 6 psi. Selecting the proper range can have a great effect on the expected output and the expected accuracy of the transmitter selection
- What kind of output signal do you need? In the building automation industry there are generally two different analog signals used, 4-20 mA and DC voltage. Transmitters are usually available in both versions. However, any 4-20 mA signal can be converted to a voltage signal with the use of a resistor.
- Do you need special protection from the elements? Many applications require special protection, such as awash-down room, corrosive environment, or an outdoor environment. Some pressure transmitters are available in various NEMA ratings or can be assembled in special NEMA rated housings that help protect them from harsh environments.
Understanding your application and selecting the right transmitter for that application will yield accurate data that will instill confidence with your customers and allow you to spend less time on old jobs and more time on new ones.
