Fluke 179 Fluke Digital Multimeters - For This AV Engineer Appearances are Not

Application Note

From the Fluke Digital Library @ www.fluke.com/library

For this A/V Engineer,

appearances are

not

deceiving

Using a DMM to test

A/V systems

For Tom Grieshaber, of Seattle-

based Vulcan, Inc., every new

audiovisual (A/V) system the

company develops is virtually a

custom project. Although each

uses many of the same compo-

nents as its predecessors, the

requirements of Vulcan’s cus-

tomers virtually guarantee that

the next system on the drawing

board will be a new adventure.

As manager of the systems-

engineering group, Grieshaber is

responsible for designing and

commissioning all of these new

A/V systems. Commissioning a

system invariably involves two

distinct processes:

Grieshaber and his team custom-built this test rack to support software burn-in and performance testing

for over 20 LCD touch panels, before installing the panels in the field. The touch panels are also a custom

manufacture, and together with a PC they run proprietary Vulcan software for controlling A/V and environ-

mental applications (from video to lighting).

1.

Set-up.

Testing system com-

ponents offline. All of the

infrastructure, core routing

components, and control sys-

tems must work, or must have

been tested to specifications.

2.

Live testing.

Testing the sys-

tem design once power is

applied, and making adjust-

ments dynamically.

Grieshaber’s process orientation

helps bring order to the more

complex process involved in sys-

tem building. Design incorporates

a wide range of technologies and

requires various control software

components (some of which are

proprietary), and a separate inte-

gration team builds each new

system from the ground up.

A first line of analysis

Although the group uses a num-

ber of specialized instruments,

perhaps the one tool that is com-

mon to all of the engineers on

Grieshaber’s team is a Fluke digi-

tal multimeter. “We typically use

a DMM to bring a system online

once it’s designed and built, or to

troubleshoot a problem that

needs preliminary engineering

analysis,” says Grieshaber.

“In a twist on a phrase, I’d say

that we bring out the DMM as a

tool for a ‘first line of analysis,’ he

says, “identifying problems when

we’re still early in the design

integration stage.”

Grieshaber says that when the

cabling infrastructure for a new

design is complete, the next step

is to isolate discrete logical blocks

so that he can then certify indi-

vidually. “At one time I may test

all of the 100 or more coaxial

cables that will go from room A

to room B,” he says. “In theory, if

not always in practice, I can do

that with my entire infrastructure

before I ever turn anything on. At

this point, by using continuity or

load testing, I’m using the DMM

to look for shorts, opens, misla-

beled cables, and similar

problems.” A common practice,

he says, is to terminate one end

of a cable with a load, view the

load from the other end, and

determine whether the load is

what he expects to see.

Fluke 179 Fluke Digital Multimeters - For This AV Engineer Appearances are Not

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