After reviewing the top 5 product considerations (pressure, media, temperature, and environment) in which the pressure transducer will be installed, it’s time to look at transducer construction, circuit design and the pressure transducer manufacturer's supply chain.
1. Construction/Robust Mechanical Design
When comparing industrial pressure transducers, look for one with an all-welded construction for a robust design. Also consider the robustness of the connectors welded on the housing. Be sure a wide selection of pressure fittings, including standards like 1/4” and 1/8” NPT as well as custom process fittings are available.
Some pressure transducers need to be protected from humidity to prevent corrosion around the pins in the connector whereas other transducer designs can be subjected to humid environments without any issues.
To isolate a gauge pressure transducer, remove the unit from the humid environment and locate it in a nearby sealed junction box where it can breathe through a cable to the atmosphere. A desiccate may also be placed in the junction box to further protect the transducer from humidity.
If the pressure transducer will be located in a harsh environment, select a unit with an ingress protection (IP) rating that satisfies the needs of the installation.
- IP65 provides complete protection from infiltration of dust and is protected from water projected from a nozzle.
- IP67 rating is protected against dust and the effects of temporary immersion of water.
- IP69K rating is for high pressure, high temperature applications.
In addition, the unit should be EMC approved to withstand electromagnetic interference. Furthermore, the construction should have high vibration and shock tolerances. When possible, avoid transducers sealed with epoxy, internal elastomers and o-rings because they do not react well with some process media like refrigerants. Also, avoid crimped or thread-sealed housings to avoid water ingress problems. Finally, look for a unit with minimal solder joints.
2. Robust Circuit Design
Sputtered thin film strain gauge technology is considered state of the art for industrial applications. This type of transducer employs the well-proven Wheatstone bridge principle. (See Image Right) In this design molecular layers are sputtered onto a 17-4 PH stainless steel diaphragm and the circuit is etched to provide excellent resistor definition and uniformity. Sputtered thin film technology allows the design of simple, highly accurate and compact strain gauges deposited onto the back of the sensing diaphragm, which is in direct contact with the media.
This method virtually eliminates drift, while offering enhanced sensitivity. Because the circuit is etched on, there is no glue or epoxy to break down or separate, which would result in measurement inaccuracy.
This circuit design offers other features such as linear temperature compensation. This is an important consideration because extreme temperature fluctuations can adversely alter a transducer’s output signal. To avoid this, a unit with temperature compensation capabilities counteracts known temperature errors in the media by electronically adjusting the transducer’s output signal.
3. Supplier’s Supply Chain and Design Control
There are many OEM pressure sensor suppliers that design and manufacture pressure transducers for industrial process environments. An industry best practices is to choose a supplier that makes most of its own components, has direct control over its printed circuit board assemblies, and has control over its supply chain. In addition, it’s recommended to purchase from a company that owns and controls the intellectual property of the transducers’ critical design components.
Suppliers that own the intellectual property of their products have the flexibility to customize a product to meet a unique situations and requirements.
In most instances, a transducer can be selected from a supplier’s catalog or website. But if it’s not a clear-cut selection—when extreme temperatures, pressures or environments are involved—it’s wise to contact the supplier to review the system.
Learn more in this free whitepaper available now: How to Select a Pressure Transducer for Industrial Applications