How often have you run into head-scratching problems with your equipment, called tech support, and been told to check the wiring. There’s a reason that tech support reps immediately want to know if you’ve checked the wiring – because it’s often the root cause of your troubles.
There are several problems that can arise from your wiring and connections that will prevent a sensor from reading properly, or stop an entire process in its tracks. We’ve seen our fair share over the years, and our support techs have a library of stories you can evoke if you’ve got the time.
So, without further ado, here are five of the most common identified in a survey by Control Design.
1 – Vibration and Loose Wiring
Vibration is common throughout industry. This can loosen terminated wires and break connections. For example, we had a customer in Central America install our heavy-duty digital pressure gauges on their pumps. However, their pump was vibrating so badly that it shook the batteries out of their sockets.
Now, a Velcro battery strap is standard on all heavy-duty gauges that use batteries. It keeps the batteries in place in even severe vibration cases.
Similarly, screw-down and spring-clamp terminal blocks prevent vibration from shaking wires loose in control instrumentation and panel boxes.
Because we have a number of customers who use our sensors in high-vibration applications, we routinely tie all internal wires down. We even fill the inside of many of our sensors with industrial potting to seal everything in place.
If you’re experiencing inexplicable problems with your equipment in and around vibrating equipment – look for loose wires and batteries. It might seem silly, but it happens to the best of us.
2 – Electrical Interference
We’ve covered this before, so pardon the broken record. However, electrical interference (EMI) is a constant problem that technicians and engineers battle on a regular basis.
It’s caused by electromagnetic fields produced by power sources and high-power electrical equipment. Electrical motors, variable frequency drives, and power sources are a common source of noise.
The solution is fairly simple, but requires diligence: route signal cables away from sources of EMI and use shielded cable for your signals. If needed, you can route your cables in metal conduit. However, the key is to make sure your cable and conduit are properly grounded.
As a rule of thumb, limit your shield grounding points to one. If you have two or more grounding points, make sure the electrical potential of each is the same. If you don’t, you may end up with ground loops that will only enhance the EMI.
3 – Corrosion and Moisture
Exposed connections are vulnerable to nearby corrosive elements, especially when moisture is present. Depending on the application, your wiring could experience airborne chemicals, cleaning agents, or salt spray, all of which will damage connectors and leads.
Using the right enclosures or properly rated equipment is crucial in any application where gases, moisture, or chemicals may be present. Se-Mar Electric’s Rich DiChristina explained to Control Design:
"We had a water treatment plant that was experiencing intermittent problems with an I/O cabinet and chassis of computer input/output cards. It was five stories underground. As soon as I got there I could smell the chlorine in the air. When I opened the cabinet, everything copper in it was green. The cabinet was vented, allowing in lots of chlorine gas."
Se-Mar had a few options, but settled on moving the panel to an air-conditioned control room and repairing the damaged components.
If moisture, chemicals, or gasses are a concern you can use sealed containers, appropriately IP or NEMA rated instruments, and the right materials to keep corrosion at bay.
4 – Labeling and Identification
Perhaps not a direct contributor to an initial problem, but definitely a big factor in downtime, the lack of proper labeling can magnify a wiring problem. If you don’t know what the wire is connected to, you’ll waste a lot of time figuring it out.
The problem is magnified when installation doesn’t follow the paper work. Cutting corners in your wiring will come back to bite you when the pressure’s on to get something fixed or replaced.
In extreme cases, software is used to sort out the details of each cable, such as where it’s connected, what signal it’s carrying (if any), etc. No matter what your method, make sure you follow the rules and stay disciplined.
5 – Stress
Not all cables created equal. If your cable needs to withstand repetitive motion, weighted suspension, or even the occasional hit from a sledgehammer, you’ll need to take special precautions to protect the integrity of your wiring.
For example, wiring on a pick and place machine will need to handle repetitive motion. Stranded cable is best.
The cable we attach to our PT-500 submersible pressure transducer includes Kevlar® strands to keep the cable from stretching if someone hangs the sensor by the cable.
Our hammer union pressure transducers often feature a protective cage around the top of the sensor to prevent oilrig workers from smashing the cable and connector with their sledgehammers when tightening the wing nut.
Wiring doesn’t exist in a vacuum. It lives in harsh environments, and the right cable for the job must be chosen or breakage will occur.
Let us know if you have any questions related to wiring your level sensors or pressure transducers. Our application experts are ready to help!
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