The selection of the best electrical connection option for a pressure transducer has a number of questions that relate. With an increase in third party agency approvals and expanded use of transducers and transmitters in commercial and industrial applications, the variety of options available can be overwhelming. In simplest terms, understanding where, who and what types of sensors are being installed are basic steps to selecting the best transducer electrical connection option.
For explosion-proof environments, a pressure transducer is typically wired into a junction box and cable is run through conduit according to the electrical code. With certain instruments, the junction box is integral to the transducer, so terminations are made within the housing. The length of the cable can be limited and electrical terminations coming directly from the transducer are limited to cable options.
Intrinsically safe and non-incendive locations do have connector options available. An intrinsically safe transmitter will require a Zener barrier whereas non-incendive approvals require conduit over the electrical connection, which can be made to an connector. Always consult local regulations regarding safety in selection of the correct connection type.
Submersible pressure transducers applications typically are installed with cable connections to allow the diaphragm to correct for barometric pressure changes at the surface (or outside of the tank). Cable is the ideal option to ensure that this occurs. It can be specified with materials that are compatible with various liquids and gases for long term use. Submersible installations, such as diesel tank level, can be considered hazardous and can also require intrinsically safe installation. Again, ensure to check safety requirements.
For sub-sea applications, connectors can be a better option. The pressure associated with submersion cannot typically be held with cable connections to prevent water ingress and thus an electrical short.
Is the pressure transducer going to be installed indoors or outdoors? Will it be subjected to high pressure wash-down or submersion? While a typical transducer looks like a piece of pipe with a thread, there are sensitive electronics internal to the housing which can have an electrical short when exposed to liquids. When selecting either option, ensure to prepare for UV resistance, possible flooding, high pressure wash down or high humidity. Gauge pressure transducers with connectors can be vented through the connector itself using a moisture barrier.
For high pressure applications, sealed gauge reference is safe option. It protects the electronics from moisture penetration (from a flood zone or mining truck that sees a pressure washer), yet prevents the transducer from correcting for barometric pressure. In higher pressure applications, barometric pressure is a smaller percentage of the overall range, so less likely to effect the overall reading.
The location of the install and the personnel assigned can make a difference in the electrical connection selection. For example, if a field technician with no formal training in pressure transducers is installing it, a connector is probably a safer option. It can reduce the risk of wiring mistakes and make a faster connection by plugging A into B. Long lengths of cable on the transducer in the wrong hands can be problematic if the cable jacket is cut by accident. This can lead to either sending the sensor back for repair, replacement, or splicing the two ends together. The replacement of a cable assembly can be much more cost effective, easier to stock and more timely.
A connector would be a preferable choice when the system might require future repair by the owner or user of equipment. Pressure transducer manufacturers for the most part offer the same or similar connection option and pin-out configurations. If MRO is a future potential, choose an connector that is fairly common and available.
On the other hand, having cable integral to the transducer can be a nice option for trained personnel. They can use the same transducer at multiple locations on site and cut the cable back for optimal lengths.
For certain industrial and OEM applications, a single piece of equipment can use various sensors. Using connectors can save time by centralizing wiring to a cable harness. In some cases, a cable with an in-line connector is also an option. It keeps the harness neat in a central location and allows the pressure transducer to reach around other items and parts.
Using different electrical connections for different parts is an added safety feature. To ensure an 100 PSI transducer is installed in one area and the 10,000 PSI transducer is put at another section, different connectors (and different process connections) can prevent issues and protect employees and system users.