5 Ways to Eliminate Ground Loops – Part I
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Most workers already know that proper grounding is a fundamental safety precaution for all kinds of electrical equipment. However, it's less well known that while grounding can prevent and resolve many safety and power issues, improper grounding can create problems in data logging, data acquisition, and measurement and control systems. One of the most common problems is known as ground loop feedback–an electrical phenomenon often resulting when different electrical circuits within a system and its peripherals have different connections or paths back to earth ground.

Ground Loop Feedback Explained

Ground loop feedback is a frequently encountered wiring issue arising when two or more connected electrical devices have more than one path to earth ground. Together, the separate paths form a loop. Electrical and magnetic fields which flow through the loop can generate unintended currents and voltages. Or, the ground points of the different devices may not be at the same potential voltage due to current and resistance in the ground path.

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Whether using different safety grounds or a safety ground and an earth ground, one of the most common examples is buzzing/humming sounds caused by currents induced in ground loops from mains (60 Hz) AC power. In video applications, users will notice this feedback in the form of onscreen stripes, while computer and networking users can experience shutdowns or gaps in their data communication.

In a worst-case scenario, this could cause an interruption in operations since many businesses heavily rely on PLCs and measurement systems for process and machine control, quality control, final test, etc.–yet ground loops often escape troubleshooting investigations and are equally neglected as a factor in many installations, arising later when electrical configuration or environmental conditions change.

Computers, data loggers, and data acquisition/control systems are normally connected to the ground through their AC power supply and the ground pin on the plug that goes into the wall outlet that shares the ground wire in common building wiring.

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Increasingly, ground loop feedback poses a threat to industrial processes given the sensitivity of newer electrical equipment. As an example, the more recent variable frequency AC drives can be controlled by an external analog voltage signal. These drives may have a sensitive input front end and when encountering noise on the control signal, the drives can experience errors or even failure.

In the upcoming part 2, find out how exactly to diagnose ground loop feedback and the five steps to reduce and prevent ground loops from occurring.
To find the ideal solution for your application-specific needs, contact a CAS Data Logger Application Specialist at (800) 956-4437 or visit us at https://www.dataloggerinc.com.