Pressure Measurement Spec & Install Best Practices

When specifying a pressure measurement system for a given application, Elden Tolman, product development engineer for Automation Products Group, says the first priority for the end-user should be to consider the environment where the equipment will be used to determine requirements for such key variables as chemical compatibility, vibration, weather-ability, pressure type (absolute, gage, sealed), power availability, communication signal output options, and field calibration. “In the case of pressure gauges, going digital offers superior accuracy and control options, such as field programming and calibration, data logging, etc.,” says Tolman.

Tolman warns users to beware of how specifications are called out and how they are applied. For example, he says some manufacturers will call out a linear accuracy of 0.25 percent of span, which may be calculated using a straight-line method or a best-fit-straight-line (BFSL) method. Some manufacturers will take a single half scale (or midpoint) measurement to do the calculation, which Tolman says can be misleading given that many pressure sensors exhibit a characteristic “S” curve. This means that if they exceed the specification, it will be worst between the zero pressure and half scale or between the half scale and full-scale pressure.

Regarding installation best practices, Tolman says pressure transducers with chassis (or case) ground call for special consideration of grounding techniques. He says, “This becomes increasingly important in applications where there is any chance of a difference in potential between the transducer and the grounding point of the control box.”

Ultimately, improper installation and/or improper use are the primary reasons for poor pressure measurement performance. As such, Tolman says it is always best to follow manufacturer’s recommendations when it comes to specification, installation and maintenance. “Sometimes people who have worked with pressure measurement for years presume they know how things should be done and trust their own experience to be correct even over a manufacturer’s recommendations and warnings,” says Tolman.

This is the second part of a two-part article on pressure measurement. To read the first part, "3 Key Pressure Measurement Technology Trends," click here.

Matt Migliore is the editor-in-chief of Flow Control magazine. He can be reached at Matt@GrandViewMedia.com.