Tuesday, January 21, 2014

Solving a repair problem with CCTV

CCTV at an airport

Closed circuit TV (CCTV) is a common necessity in public places, like airports, casinos or even supermarkets.  Generally speaking they are inconspicuous.  Often they are covered by an opaque dome. But, they are also hard to reach, by design.  To achieve the wide viewing coverage and for the protection from vandalism CCTVs are typically positioned high up and out of reach.  This makes for a difficult job to install or maintain them.  One of Agilent’s customers SSSTV in Las Vegas is in this business.  He told us about some of his challenges.

Indoor CCTV

CCTVs are powered by external power supplies, either 24 VAC or 12 VDC, +/- 10%.  It should be a simple task setting the right voltage at the power supply such that the correct voltage would result at the camera base.  However, the physical world may not always cooperate.

In most cases, there is a long power cable running between the protected cabinet with the power supply to the camera location.  There is an inevitable voltage drop along the way due to resistance in the conductors carrying power to the camera.  In an extreme case, the CCTV is on top of a light pole outdoors and the power supply is safely covered indoors.  The long wire is subjected to severe temperature cycling from the weather.  The nominal temperature range of Las Vegas can go from freezing winter to 106oF (41oC) in the summer.   Heat build up from the sun’s radiation can exacerbate the situation.  Soon customer would report camera malfunctions, possibly due to insufficient power supply at the camera base.

CCTV over parking lot

Often, after taking care to fix other issues, he would have to readjust the power supply so as to provide exactly 24 VAC at the camera base.  He would alternate between taking voltage readings with his meter at the camera base and making the power supply adjustment.  Mostly, it is a matter of climbing up and down long ladders a few times.

With Agilent’s WRC (wireless remote connectivity) meter, he is now able to see the meter readings as he adjusts the power supply.  He leaves his Agilent meter connected to the power input at the camera base.  The meter reading is transmitted via a Bluetooth adapter to his Android cell phone.  The app is free from Agilent or Google Play Store.  It just takes a few clicks to get going. No more climbing up and down ladders.

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