Security Sales & Integration

October 2012

SSI serves security installing contractors providing systems and services; surveillance, access control, biometrics, fire alarm and home control/automation. Coverage in commercial and residential product applications, designs, techniques, operations.

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T e failure of proper analysis is in the lack of asking all the troubleshooting questions. T e one major question missed in this situation was: When does the problem occur? In this case, the interference only occurs during nighttime hours. Normally, a ground loop is constant and does not vary between day and night. T is image appears to again be a 60Hz problem; however, it is actually more likely to be AC hum induction. One cause of AC hum is video cable picking up magnetic and electrostatic hum fi elds radiated by power wiring. T is is caused by a video cable in close vicinity to a 100/220VAC power source. Locating this problem can be time- consuming, especially if you are not familiar with the overall installation. Here is a little help in determining whether the interference is a ground loop or AC hum: If the two areas of distortion on the video image are the same shape, size and usually color, the problem is hum induction. If the two areas of distortion are diff erent shape, size or color that usually indicates a ground loop situation. Let's move on to the next problem. Figure 3: Noisy Power old? When does the problem occur? What type of transmission method is incorporated and is it in conduit? Is the interference constant or intermittent, and what is the color of the lines of interference? devices such as air handling units, any type of motor generator device and even mechanical punch clocks used at many workplaces. T ere are two basic solutions to this problem. First, locate a diff erent power What is the age of the system? R New When does the problem occur? R Day Transmission method? Conduit? Interference? Color of interference? In this case, we have white lines randomly across the screen. T e system has been installed for more than a year, and the interference comes and goes anytime throughout a 24-hour time period. T e video transmission method is active UTP. After reviewing the image, we see If lines are white, the problem is induced directly into the camera equipment, normally via the AC input power. This is typically referred to as dirty or noisy power. CASE NO. 3: COLOR HOLDS CLUES In looking at the troubleshooting challenge of Figure 3, let's review the questions. Is the system new or that the number of interference lines can easily be counted; therefore we can rule out high- frequency sources such as RFI or microwave as the probable culprit. What does the color of the lines of interference indicate? A few facts of information may help in solving this problem. If the lines of interference are gray or black, the problem is usually induced into the cable transmission method used by the camera system. If the lines power in AC are white, the problem is induced directly into the camera equipment, normally via the AC input power. T is situation is typically referred to as dirty or noisy power. T is situation is caused by the camera equipment being fed by a power source that also powers other Example of a Troubleshooting Checklist R Old R Coax R Yes R Night R Both R UTP R No R Constant R Varies R Gray R Fiber R Black R White input source for the camera, preferably one that is conditioned and free of noise spikes. T e second choice would be to insert an AC line noise fi lter. T is fi lter will eliminate any spikes of energy on the AC power line from reaching the camera. Inline AC Noise Filter LINE LOAD Camera equipment An AC line noise filter keeps energy spikes from reaching cameras. In the past, most cameras were VAC; now DC-powered and dual-input voltage cameras are popular. Courtesy Radius Power It should be noted that in the past most surveillance cameras operated on VAC; however, DC-powered and dual- input voltage cameras are becoming OCTOBER 2012 / SECURITYSALES.COM / A5 ss1012dumies.indd A5 9/26/12 1:45 PM

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