Security Becomes Big-Screen Sensation
What is the one key piece of equipment that is seen these days in all integrated systems, whether it is CCTV, fire, access control, central stations, or even mass evacuation? The device is the security monitor. This month we will take a closer look at not only the proven cathode ray tube (CRT) monitor we have learned to love, and hate, through the years, but on a more exciting note, the newer flat-screen LCD (liquid crystal display) monitors that are now popping up everywhere.
Recently, I joined the trendy multimonitor crowd by installing two LCD monitors on the computer in my office. As many of you already know, Microsoft® Windows™ operating systems such as XP™ and Vista™, allow a computer user to have a two or three monitor desktop. Even though I have been working with various firms selling multimonitor workstations for some time, it took a while for yours truly to catch up with the Joneses so to speak.
The first question I asked myself after working a few days with two monitors is, “Why didn’t I do this a long time ago?” The increase in productivity is phenomenal. Take my advice; if you are a procrastinator like me and haven’t done this yet, and are not selling your customers on the option of multiple monitor workstations, you are both missing the boat. Do it today!
Technically, both old and new monitors do not, and have not gotten, the attention they deserve. We can install a very elaborate CCTV or monitoring system. However, if the video monitors are not properly selected, installed and maintained, (Do you have service contracts?) your design and hard work will be diminished.
Make Sure Systems Are Grounded
Make sure that video monitors are properly grounded. Monitors with metal chassis have the potential to give a dangerous shock. I can remember a situation in the past where a person who had a monitor tucked in the back of a fast-food kitchen decided to connect the monitor with a two-prong extension cord. This resulted in an employee getting a very dangerous shock. First, the monitor never should have been in a dangerous wet area, and secondly, it should have been grounded properly.
Speaking of proper grounding, are you grounding your camera coax runs only at the head-end? This avoids bad picture quality from ground loops as we have discussed in earlier “Tech Talk” articles.
Poor pictures on monitors can also come from improper cable termination. If you have more than one CCTV analog monitor to connect, avoid using coaxial “T-Tap” style connectors. Use monitors that are equipped with a looping coaxial connection and loop through the monitors, making sure the last monitor in the loop is the only one with the 75-ohm termination switch selected.
How to Adjust Your Monitors
Adjusting CRT analog monitors properly has always been a challenge. There are typically four adjustments:
Horizontal hold — This adjusts the phase of the horizontal sync. This signal can become unstable from such things as a large signal voltage drop due to too long of a coax run or high frequency losses due to high capacitance.
Vertical hold — This adjusts the vertical sync phase. If cameras are not synchronized properly, you can get a “picture-roll” effect when using camera switchers. I have seen this corrected sometimes by reversing the phase to a camera by just simply reversing the power transformer leads to that camera. Cheaper monitors sometimes have more problems with vertical hold.
Contrast — This is an adjustment of the dynamic range of the electron beam. The range is from black or higher contrast to white or lower contrast. Room lighting is a major influence on this adjustment. I always recommend some background room lighting, as it will make viewing easier on the eyes. Contrast ratios are important in specifying LCD performance. A good minimum contrast ratio is 400 to 1.
I have found some freebee LCD monitor test programs on the Net. Get one that gives you all black and see how much back light gets through. You will see a big difference on cheaper LCD monitors. I have even heard that one of these programs can try shaking a bad pixel loose, though I have not seen this in action. Let me know if it really works. Several of these free monitor test programs I am referring to here can be found at www.benchmark hq.ru/english.html?/be_monitor.html.
Brightness — This adjusts the DC level of the electron beam while trying to maintain the contrast dynamic range. Brightness is adjusted to make the picture look more natural.
According to Vlado Damjanovski, CCTV expert and author of “CCTV, Networking and Digital Technology” (2nd edition), “A simple rule of thumb is to have the brightness and contrast adjusted so that the viewer can see as many picture details as possible.” To help with adjustments Vlado recommends a handy tester such as the TG-8 test pattern generator found at www.cctvlabs.com.
Flat Screens Surpass CRT Monitors
Now let’s talk about the exciting new kid on the block, the LCD flat-screen monitor. There are basically two types of LCD monitors: the passive dual-screen twisted nematic (DSTN) and the highly popular active matrix Thin Film Transistor (TFT).
LCD screens are made up of several layers of colored and polarizing filters, liquid crystals, glass alignment layers and a fluorescent backlight illuminator. Red, green and blue liquid crystal chambers let the backlight through and make up each pixel on the screen.
Early versions of LCD monitors had trouble with things like bad pixels and low contrast. This has improved considerably in newer models. The LCD monitor runs at a cooler temperature, has a lower profile and draws less dust than the high voltage flyback circuits in CRT monitors.
Backlights in LCDs will last about 20,000 to 30,000 hours compared to CRT tube life of 10,000 to 20,000 hours. The LCD backlights are cheaper and easier to replace as well.
This brings up one belated reminder on servicing CRT monitors. Know what you are doing if you work inside a CRT monitor. The capacitive nature of a CRT will still throw you across the room if not properly discharged first. Older techs know this, but younger ones may not, so be warned. The stored voltage after turning off a CRT monitor is deadly, and if the tube, which is in a vacuum, is cracked in handling it can implode and send the sharp electron gun right into you.
If you thought LCD monitors were a big deal then look out for the plasma displays. We have seen them in the hot home entertainment market, but have you considered them for the commercial security market. Simply put, plasma displays consist of many tiny cells located between two panels of glass. This glass holds an inert gas mixture of neon and xenon.
As LCD displays get bigger and the cost of plasma displays drop, new markets have opened up for security dealers in digital signage applications. Integrate digital signage in with your next mass evacuation system.
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