How Do You Gauge AV Performance?

• By Will Craig
• 01/31/06

Gauging the performance of AV equipment is often a subjective experience. For product demonstrations, we all have our own ideas about good, better, and best (and 'bad') when listening to loudspeakers or examining a projected image. Likewise, with service complaints from end-users, "issues" can be subjective to the user. And, when determining whether a contractor has fully met the terms of their specifications for installing new systems, it is helpful to have something besides subjective experience with which to accept or reject their work. There are a number of handy tools that can help with taking measurements and making observations that can bring objectivity to a subjective process of evaluating AV equipment, rooms, and systems.

The first device that a campus technologist should have in their kit is a test signal generator. These will help you in troubleshooting situations, both by providing a live signal in the desired format, but also through using test patterns to identify problems and shortcomings in AV systems. The one in my tool bag is an Extron VTG-300R, which generates a wide variety of audio and video/graphics test signals and has a rechargeable NiMH battery. This makes it convenient to use it for testing and commissioning a large number of outlets and systems without needing to be constantly plugging and unplugging a wall wart or power plug. Similar products in the $200-$1200 range include the Multidyne TS-12 (no graphics), and the Kramer VP-810 (no video, color bars only). The Extron VTG-400 takes the features of the VTG-300 to the next level with additional output scan rates and video test patterns, for another $1000 in cost.

A common application for the graphics capabilities of an Extron test generator is to use a field of single-pixel cross-hatched lines to detect skew problems, which are common when using CAT-5/5e/6 UTP transmitters and cabling that has been improperly installed and/or configured.

The audio tone can be used to quickly check laptop audio input jacks to verify audio-follow-video switching, and can provide a constant tone for checking loudspeaker output. Several times I have found during college/university system checks that the contractor neglected to wire one or more loudspeakers - Oops!

A basic sound level meter can be a useful tool in certain situations, especially when explaining to the facility manager why it is important for the mechanical systems to be quieter in an upcoming renovation project. Another application would be testing whether sound reinforcement systems are providing suitable amplification of voice or program audio over ambient background noise. A good starting point would be the Extech #407740 for around $200 (www.extech.com ), through there are plenty of good choices.

For more detailed audio analysis in a convenient, handheld package, I like the Terrasonde audio toolbox series. Their audio products are handheld, rugged, and provide a surprising number of audio analysis features for the price.

Light level meters are useful for tweaking lighting in existing rooms, and for measuring whether the amount of light that you requested for your new distance learning room has actually been provided by your lighting designer or electrical engineer. When you ask for 50 foot-candles on the instructor's face and you only get 25, the light meter is critical to getting things fixed right away, and on someone else's dime. I use an Extech Q527, but there are plenty of models that are good for general-purpose measurements between $100 and $200.

All of these testing devices can pay for themselves quickly if put to good use. An annual budget of $500-$1000 for AV test equipment could deploy all of the types of test gear mentioned in this article within three years. And, through identifying problems using objective criteria and getting them fixed, you can spend your time money on more fun pursuits--like those new product demonstrations.

Links to vendors mentioned in this article:
www.extron.com
www.kramerelectronics.com
www.extech.com
www.multidyne.com
www.terrasonde.com