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Commissioning AV Systems

Earlier this year, InfoComm International published the newest edition of its AV Installation Handbook, with new Also new is a detailed Commissioning Tests Checklist, developed by the Project Commissioning Working Group.

About the Checklist

Earlier this year, InfoComm International published the newest edition of its AV Installation Handbook, with new sections on audio, video, and control systems. Also new is a detailed Commissioning Tests Checklist, developed by the Project Commissioning Working Group. Not all tests are required for all systems. Ultimately, commissioning should be based on an agreement between client and designer. For more detail, you can download the list at www.infocomm.org.

Checking the Physical Installation

Equipment Inventory. Is all the equipment in shop or on site? List all equipment in the system that is not present and why.

Racks and Rack Cleanliness. Is all rackable equipment installed? Ensure all racks are clean, particularly of grease markings, etc., and that blanks and vents are installed in unused rack spaces.

Rack Thermals. Ensure you've inspected the rack's thermal gradient performance and checked that all equipment is operating within the manufacturers' guidelines.

Patch Bays. Make sure all patch bays are labeled and that patch bays are configured so that all outputs are in the top rows and inputs are in the bottom rows.

Cable Management

Tie Wraps. Make sure tie wraps aren't so tight that they could deform the cable. Unshielded twisted pair (UTP) cables should be laced and bound with Velcro ties.

Future-Proof Terminations. Terminations should have sufficient service loop to allow for re-terminating without having to open a cable bundle or a pathway to lay a new cable.

Dressed and Bundled. Verify that cables have been dressed appropriately and bundled according to type. Cables should also have appropriate separation
according to signal type and level.

Labeling Cables. Make sure all cables have clearly legible, unambiguous labels that are visible without having to take apart the system or the cable bundles. Cable labels should be permanent and non-slipping.

Audio Performance

Harmonic Distortion. Measure the total harmonic distortion of the audio system. The distortion level should not exceed industry best practices.

Signal-to-Noise. Measure the signal-to-noise ratio of the audio system. The noise level should not exceed industry best practices.

Frequency Response. Measure the system's frequency response for speech sound reinforcement, which should be determined during design. Also measure frequency response for program sound amplification.

Speaker Polarity. Program loudspeakers in the same system should produce consistent polarity for a mono input signal in all channels. Speech reinforcement systems should be polarized so that positive acoustic pressure on a microphone results in
positive acoustic pressure at all loudspeakers.

Multiple Sources. Calibrate audio system inputs so that there is zero or minimal difference between any input signal level.

Conferencing Systems. When working on a conferencing system, adjust the microphone input gain to demonstrate that a standard talker, positioned at each talker position in the room, produces a dBu level of zero at the output bus of the digital signal processor. Verify signal levels for both transmitting and receiving normal speech.

Amplifier Loads. Make sure no power amplifier exceeds its rated load. Record the impedance (and at what frequency) for each loudspeaker line of each power amp. If available, 63, 250, and 1,000 Hz are recommended.

Video Performance

NTSC Signal Gain. For NTSC sources, you should demonstrate that a consistent, 1-volt, peak-to-peak test signal at each source produces a 1-volt, peak-to-peak to each destination. Verify at each destination using NTSC bars, peak white, and five-step multiburst.

RGBHV Signal Gain. For RGB sources, you should demonstrate consistent 700 mV from each source to each destination. Observe results using a flat-field pattern signal at 1,024x768 resolution. Measure peak-to-peak voltage using a 200 MHz oscilloscope.

Projected Displays. Verify that projected displays are focused, centered, and evenly illuminated. Using a light meter, make sure a projected image has uniform brightness across the whole image, and measure the contrast ratio with ambient lighting in normal operating mode.

Multiple Resolutions. The video system should be able to display stable, properly scaled images with no artifacts when switching among, at minimum, 1,024x768, 1,280x1,024, and 1,280x720 sources, plus all sources in the performance criteria.

Source: AV Installation Handbook: Best Practices For Quality Audiovisual Systems, Second Edition, Infocomm International (www.infocomm.org.)



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