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1.5
Displays and controls
ZoneGuard systems include an 8-character LCD readout
located at the controller which is used to display gas
readings and other messages. Built-in LED alarm lights are
used to indicate “OK” / Power-on (green), “Low Alarm”
(amber), and “High Alarm” (red) conditions.
The On/Off “Mode” button is to initiate the automatic
calibration sequence and to control most other day-to-day
procedures. The button is located on the exterior of the
controller housing, on the underside of the case. Four
additional push-button controls (“-”, “+”, “Alarm” and “Cal”)
are located on the inside of the controller housing door.
These buttons are used for advanced procedures such as
changing operating modes, changing alarm setpoints,
adjusting calibration gas values, making optional setup
choices, and other advanced procedures.
1.6 Alarm
Logic
The Zoneguard personal, portable
gas detector has been designed for the detection of
dangerous atmospheric conditions. An alarm condition
indicates the presence of a potentially life-threatening
hazard and should be taken very seriously. Failure to
immediately leave the area during an alarm condition
may result in serious injury or death.
In the event of an alarm condition it is important to
follow established procedures. The safest course of
action is to immediately leave the affected area, and
return only after further testing together with other
appropriate safety procedures determine that the area
is once again safe for entry.
ZoneGuard alarms are user adjustable and may be set
anywhere within the range of the specific sensor. When an
alarm set point is exceeded the audible alarm sounds, the
appropriate bright LED alarm light indicator are turned-on,
and (if equipped) the optional external strobe light(s) and/or
remote high intensity audible alarm are activated. (Any
external alarm devices controlled by means of the
ZoneGuard alarm relay contacts will also be activated.)
ZoneGuard alarms are normally of the self-resetting type.
When readings drop back below the pre-set alarm levels,
the instrument returns to normal operation, and the visual
and audible alarms cease.
It is possible to set ZoneGuard alarms so that they "latch".
In the latched condition, once an alarm occurs both visual
and audible alarms will continue to sound even after the
atmospheric hazard has cleared. The instrument must be
manually reset before the alarms are silenced.
Procedures for latching ZoneGuard alarms are given in
Chapter 4.
ZoneGuard systems equipped with toxic or combustible gas
sensors are provided with two levels of gas alarm: “Low”
(warning) and “High” (danger). Toxic and combustible
alarms are configured as “ascending”, meaning that they are
triggered when gas concentrations exceed the alarm
setpoints.
ZoneGuard systems equipped with oxygen sensors have
four levels of gas alarm, two “ascending” alarms (“Warning”
and “Danger”) for oxygen enrichment, and two “descending”
(“Warning” and “Danger”) alarms for oxygen deficiencies.
Descending alarms are activated when oxygen
concentrations drop below the alarm setpoints for oxygen
deficiency.
Note: “Warning” level alarms may be manually
acknowledged and silenced for a period of 10 minutes
by pressing the Mode button. If the alarm condition
continues to exist after 10 minutes has elapsed, the
“Warning” alarms will be reactivated. If the alarm
condition reaches the “Danger” level during this 10
minute period, the “Danger” level alarms will
immediately be activated regardless of whether or not
the “Warning” alarm has been silenced. “Danger” level
alarms may not be manually silenced.
The procedures for adjusting alarm setpoints are given
in Chapter 4.
1.7
Special microprocessor features
Several automatic programs prevent tampering and misuse
of the ZoneGuard by unauthorized persons. Each time the
detector is turned on, an electronic self-test is performed
that assures the user of proper performance.
Optional setup choices include latching alarms, changing the
concentration of the gas that is used during Auto Calibration
adjustment, as well as changing or restoring the factory
alarm settings by using the 4 push-buttons on the instrument
keypad. It is also possible to enable or disable use of the
external Mode button.
ZoneGuard software also includes an “Alarm Test” function
that can be used to automatically “ramp” readings
throughout the full range of the sensor. The “Alarm Test”
function is used to verify alarm setpoints as well as the
proper activation of the audible alarm, LED alarm light
indicators, optional strobe lights or horn, as well as other
alarm devices or peripheral equipment controlled by means
of the ZoneGuard relay contacts.
Chapters 4 and 5 describe how to use these advanced
technical features and setup choices in greater detail.
1.8
Relays and outputs
See Appendix F for ZoneGuard electrical schematics
and wiring diagrams.
1.8.1 VAC relay contacts
ZoneGuard systems include DPDT relay contacts for
warning (low) and danger (high) gas alarm conditions.
ZoneGuard relay contacts are rated at 5 Amp at 250 VAC,
non-inductive load.
1.8.2 VDC
outputs
ZoneGuard systems also i12 VDC outputs rated at
0.5 Amp for warning (low) and danger (high) gas alarm
conditions.
