Rolling Picture Bars

The problem comes about because both the AC power source and the CCTV installation have one or more common points of connection and thus cause a Ground Loop. These are usually due to improper grounding of AC plugs to a metallic portion of the structure. The real problem to the CCTV industry is that these AC ground currents will change with poor load balances and so the problems caused by a ground loop may be practically invisible one minute and intolerable the next. Due to the analog to digital conversion of video into still frames, DVR systems are more sensitive to “rolling power bars” than conventional analog monitors, time-lapse VCRs and multiplexers.

The easiest and most effective solution is to connect a “Power Conditioner” at each point in the system where grounded AC power is attached (all grounded cameras, lightning arresters, patch panels, required coaxial cable grounds, and any other possible source of grounding). A power conditioner (also known as a line conditioner) is an electronic device, commonly taking the form of a power strip, that smooths out the peaks and dips of AC power to create smooth power for precision electronics. Power conditioners are different from the typical uninterruptible power supply in that they continuously charge the battery and constantly run the equipment off battery power. Most UPSs simply pass the source power straight through while the source power is live. This can cause some sensitive equipment to fault or perhaps even be damaged in extreme cases. A dual conversion on-line UPS is a kind of power conditioner.

With a clear understanding of the source of these “rolling power bars”, and the exact situation that introduces this interference into CCTV systems, the CCTV Installer can assemble even a complex system with the confidence that no ground loops will interfere with the transmission of clear pictures.

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