4
Operation
The Sentry features a large bar-graph VU meter with 23dB range to give a good visual indication of
the noise level in a venue.
While the meter is operating in the green section, with even an occasional peak into the red, there is
no cause for concern. Factory set the Sentry has about 20 seconds delay when limit is just exceeded
before power is removed to allow performers time to reduce sound levels.
The Sentry will operate within the range 80dB - 120dB and may be pre-set to anywhere in this range.
Provision is included to operate at 2 different levels, for instance at different times of day. This
selection can be performed manually or automatically by a time switch. A front panel indicator shows
when level 2 is selected.
If a mains warning lamp is connected it will operate at the same point as the two red sections of the
meter. These are labelled "WARNING".
If the noise level is high enough to light the "OVER LIMIT" section of the meter (three red sections)
the noise has exceeded the allowable limit. If this is allowed to continue for more than the set time
period (about 20 seconds factory set) the unit will trip and remove the power to the contactor or relay.
Visual indication of this is provided above the reset button.
When the unit is first powered up the RESET indicator will be lit - wait for a few seconds and press
the reset button. The Sentry will now be reset and ready for normal operation.
The action of the timing circuit means that continually exceeding the limit even for short periods may
eventually trip the unit.
The unit has to be manually reset to restore power and this will only be possible after a short time.
The reset time is determined by the amount by which the unit is driven over limit. e.g. tripping the unit
by just exceeding the limit will result in a short period of a few seconds before reset is possible.
Tripping the unit by grossly exceeding the limit will require a longer period before reset is possible.
NOTE. It is important that a check is made before the unit is reset.
Check that it is safe to do so (eg are amps turned down).
Audio systems generally need to be powered up in a specific order. In an audio system comprising
of different components amplifiers, mixers, etc. a general rule is to switch power amplifiers off first
and on last to avoid possible loudspeaker damage. Therefore a band or D.J. may need to turn off
amplification equipment to protect loudspeakers before the power is restored.
All connections and adjustments are located beneath the removable cover plate (below the display).
Non reusable security labels are supplied with each unit to help detect unauthorised tampering.
Level 2
Level 2 is selected by shorting the 2 marked terminals on the Sentry grey connector strip. Switch may
be via switch or relay etc, the timer option is detailed below. The allowed level at weekends or
evenings may be different so the level 2 facility allows a quick switch.
Opening windows and/or doors allows more sound out of a venue, setting level 1 about 6dB lower
than level 2 and using magnet relays on doors/windows as the level 2 switch means running at level
2 (louder) as long as doors/windows shut and dropping to level 1 if opened.
