Cloud VTX-WM1, Инструкция по установке и эксплуатации

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VTX-WM1 Installation Guide v1.1
13
Impedance Tests
The VTX-WM1 card includes a variable
frequency test oscillator which may be
programmed to apply a test tone (at 40 dB
below the amplifier’s maximum output level) to
the amplifier output at a future date and time,
and, if desired, at regular intervals thereafter.
(It is recommended that tests are scheduled
for the hours of building non-occupation).
The amplifier output voltage and current are
monitored during the test and hence the load
impedance checked. This gives the engineer
a first-line confirmation that all the speakers
connected to each amplifier channel are
present, connected and functional.
Clicking
Tests
(click the amplifier button
first) opens the
Test List
page for the
amplifier:
In order for the impedance tests to be
meaningful, an initial Load Configuration
test must be run, to establish a reference
impedance at the frequency to be used. The
upper pane of the Test List page is concerned
with this initialisation.
Configuring the Load
The amplifier must be powered on and each
channel connected correctly to its normal
speaker(s). Select each channel in use from
the drop-down list under
Channel
. (If any
channels are in Bridge Mode, select the lower-
numbered channel of the pair.) Select the
frequency to be used for the test from the
drop-down list under
Frequency
. If using a
bi-amped (or tri-amped, etc.) speaker system,
the frequency for each channel will need to
chosen to match the relevant driver type. The
frequency selected should be approximately in
the middle of the frequency response range of
the speakers/drivers connected to the channel.
Consideration should be also be taken of any
loudspeaker enclosure resonant frequencies
– these may be particularly evident at low
frequencies, and should be avoided, as their use
will give misleading results.
Click the
Config
button. This will generate
a dialogue box warning that a test tone is
about to be fed through the audio system.
Click
OK
if you are happy for this to occur.
A progress bar is displayed, and when the
test is complete an impedance value will be
displayed in the
Expected
field. To re-check
the expected value, set a
Tolerance
value
(30% is recommended initially) and click the
Test
button. A second test will be run, and
the results displayed.
The
Remove
button may be used to cancel
the current reference impedance value for the
selected channel. This should be done if, for
example, a loudspeaker has been removed or
replaced.