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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.

Ground loop feedback is a common electrical problem caused by different circuits within a system having varying connections to earth's ground. This can lead to intermittent issues based on seasonal conditions. CAS DataLoggers' Application Specialists have put together an introduction to help understand this phenomenon.

Ground Loop Feedback Explained

Ground loop feedback occurs when connected electrical devices have multiple paths to the earth's ground, forming a loop. This can result in unintended currents and voltages, as well as differing ground potentials between devices. This discrepancy can manifest as measurement offsets or signal noise, disrupting normal operation.

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Induced currents in ground loops from mains AC power cause buzzing or humming sounds. In video, they create onscreen stripes, while computer and networking users may experience shutdowns or communication gaps. Engineers and technicians also notice offsets or noise in their data. Neglecting ground loops disrupts operations for businesses, often overlooked during installations.

Computers and data devices are typically connected to the ground through power supplies and data cables. Ethernet cables maintain ground isolation, but RS232 cables have their own ground conductor. This can create a ground loop if devices are in different areas of a building.

A computer can control manufacturing equipment but may need a different power source than the machine. Each breaker panel has its own ground stakes, ideally with no resistance. However, resistance can occur, causing erratic operation or shutdown of the computer and the equipment it controls. Ground loops can impact low-level measurements due to cabling. Shielded cables are usually used for sensitive measurements to protect the signal from electromagnetic interference. The shield should be connected to the ground at only one end to collect interference and keep the signal clean. If connected at both ends, it creates a potential ground loop, allowing interference to couple to the measured signal as electrical noise.

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Ground loop feedback increasingly threatens industrial processes due to the sensitivity of newer electrical equipment. For instance, external analog voltage signals can control recent variable frequency AC drives. If these drives encounter noise on the control signal, they may experience errors or failure.

In the upcoming part 2, find out how exactly to diagnose ground loop feedback as well as five steps to reduce and prevent ground loops from occurring.

For more information on ground loops, or to find the ideal solution for your application-specific needs, contact a CAS DataLogger Application Specialist at (800) 956-4437 or visit us at https://www.dataloggerinc.com.