PureAire Monitoring Systems, Inc.
10/25/07
13
4: Normal Operation
The
Air Check
✓
EX
is a single point monitoring system designed for the
continuous detection and measurement of toxic gas leaks.
4.1 Power Up Delay
The
Air Check
✓
EX
incorporates a power up delay that holds the analog output
at 4 mA for one minute after power is applied. This allows the sensor to stabilize
and reduces the possibility of triggering an erroneous alarm.
4.1.1 Sensor Poisoning
It is important to understand that all catalytic sensors may be poisoned, causing
loss of sensitivity. Silicon, sulfur and lead containing compounds are especially
detrimental. All combustible gas detectors operating in these environments
should be calibrated more frequently.
4.2 Concentration Display
This is a real time display of the measured concentration of the target gas. The
concentration value appears on the LCD; the target gas and unit of measure
(PPM, PPB, etc.) are indicated adjacent to the digital display.
When the instrument is in the normal monitoring mode, the left arrow indicator
on the LCD will be “off.” Should the measured concentration exceed the range of
the instrument however, the left arrow indicator will flash rapidly and three
horizontal dashes (
- - -
) will appear on the LCD.
4.3 Analog Output
During normal operation, outputs an analog signal directly proportional to the
measured gas concentration, with 4 mA being “0” and 20 mA being full scale.
4.4 Fault Alarm
The
Air Check
✓
EX
features a self-supervised gas sensing system which alerts
the operator to sensor faults, such as a missing sensor, or negative drift. In the
event a sensor fault is detected, the analog output will drop to 0 mA, FLt will
appear on the local digital readout, and the red Keypad/Fault LED will flash at
one second intervals. If the instrument is configured with the alarm relay option,
the Alarm 3 (Fault) relay will also be activated.
4.5 Concentration Alarms
If the
Air Check
✓
EX
is equipped with the Alarm Relay option, the appropriate
Alarm 1 or Alarm 2 relay will activate when the measured gas concentration
exceeds the alarm setpoint.
