Application Summary
During the early years of television broadcasting, video production and distribution consisted primarily of moving the video signal from the camera where it was created to the transmitter where it was broadcast. Monitors connected to each camera were installed in the control room to help operators select the camera angle, and a few other monitors displayed the health of the video image before transmission. Technicians also checked oscilloscope displays of the composite video signal to ensure that it met NTSC standards.

Today, however, video signals are distributed over wider areas and go through much more processing than this. The signals are not only generated by cameras, but are often synthesized, manipulated, recorded, and re-recorded. Also, the signals are both analog and digital, so processing includes distributing the video signal over many more channels with more opportunities for failures along the way. Monitoring the health of these video signals requires an automatic system that lets technicians go about their daily tasks without constantly watching a monitor. Some highly sophisticated and dedicated diagnostic systems are available to do the job, but they are very expensive which forces some distribution amplifier manufacturers to look for less pricey, but reliable alternative solutions.

IOtech’s Solution
One such company, PatchAmp Corp., Hackensack, N.J., came up with a novel approach using IOtech Personal Daq/56 modules. The modules comprise a data acquisition system with USB connections hubbed to a central computer. They also contain analog and digital signal inputs for signal processing, recording, and alarming. PatchAmp builds video distribution amplifiers for numerous applications in studios, TV stations, and remote locations. It must ensure complete signal reliability, nearly 100% uptime, which is not an easy task.

The company uses Personal Daq/56 modules, about the size of a Palm Pilot, and DASYLab^® software to look for several types of common video failures, including frozen images, lost video signals, or completely black, green, or blue screens. The signals don’t require a high bandwidth, so PatchAmp converts all digital signals to an analog representation, and then rectifies the signal to obtain a varying DC voltage. Under the direction of built-in proprietary algorithms, the system analyzes the voltage and identifies each type of failure. The equipment is programmed to alarm each failure, and it directs technicians to the faulted rack instead of letting them search the entire site, which often hosts 100 or more individual channels.

Another type of fault is a hardware failure. Here, the failure is called a summing fault, detected by hardwired circuitry built onto the distribution amplifier card. These faults are activated when a card “dies,” or starts drawing excessive current if the air conditioning fails. Other hard faults such as lost signals and improper data are also summed together and trigger an alarm. But a frozen or black picture, for example, is not a part of the summary fault, so the Personal Daq/56 detects it.

One IOtech Personal Daq/56 data acquisition system connects to either a 24 or 32-channel PatchAmp distribution amplifier or one chassis. Often, however, two Personal Daq/56s are used in the 32-channel systems to double the acquisition speed. A Personal Daq/56 contains 16 digital I/O ports, four frequency channels, and 20 analog channels. Using the IOtech PDQ1 expansion module increases the capacity to 40 analog and 32 digital channels. The largest PatchAmp frame contains 32 amplifiers, so this is a perfect fit. Eight spare analog channels are then available for measuring power supply voltage and frame temperatures, and the four frequency channels monitor the fans’ speed.

Conclusion
Numerous PatchAmp video distribution amplifiers have been in continuous use for three or four years, and none have ever failed. The Personal Daq/56 system was selected because it is also highly reliable, fits the distribution amplifiers well, works easily with the software package, is small, and runs independently of the PatchAmp frame power supply.

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