8
combustible sensor located in a 100 percent
pure combustible gas or vapor environment
containing no oxygen will be unable to burn
the combustible gas and will produce a
reading of zero percent LEL.
1.4
One Button Auto Calibration
The Ex Chek detector has been designed
for easy verification of accuracy.
Biosystems’ “One Button” calibration logic
means that all normal day-to-day operating
procedures, including automatic calibration
adjustment, may be undertaken through the
use of the single on/off MODE button.
The accuracy of Ex
Chek instruments should be checked
periodically with known concentration
calibration gas. Failure to check
accuracy can lead to inaccurate and
potentially dangerous readings.
Calibration is a two step procedure. In the
first step the Ex Chek is taken to an area
where the atmosphere is fresh and a "
zero
"
adjustment is made by pressing the on/off
MODE button. The second step of the
calibration procedure is the sensor response
or "
span
" adjustment. In this step the
sensor is exposed to known concentration
calibration gas. If the instrument recognizes
a deviation from the expected response, it
will automatically adjust itself so that the
readings match the concentration of the gas
being used.
Calibration procedures are discussed in
detail in Chapter 3.
1.5
Display backlight
A manually activated display backlight
allows the LCD to be read even in dim light
conditions. Pressing the on/off MODE
button once at any time during normal
operation causes the backlight to be
activated for 10 seconds. In the event of a
gas alarm the backlight turns on
automatically and remains on until the alarm
condition has cleared.
1.6
Alarm logic
Ex Chek alarms are user adjustable and
may be set anywhere within the range of the
sensor. When an alarm set point is
exceeded a two-toned audible alarm
sounds, a bright red LED alarm light flashes,
and (if equipped) the optional vibrator type
alarm is activated.
Ex Chek alarms are normally self-resetting.
When readings drop back below the pre-set
alarm levels, the instrument returns to
normal operation, and the visual and audible
alarms cease.
Ex Chek alarms can also be set to "latch"
during an alarm condition. In the “latched”
mode, once an alarm occurs both visual and
audible alarms continue to sound even after
the atmospheric hazard has cleared. The
alarms must then be manually reset by
pressing the MODE button.
Procedures for latching Ex Chek alarms
are given in section 4.2.
1.6.1 Atmospheric hazard alarms
The Ex Chek personal,
portable gas detector has been designed
for the detection of combustible gas
accumulations. An alarm condition
indicates the presence of a potentially
life-threatening hazard and should be
taken very seriously.
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 to return only after
further testing determines that the area is
once again safe for entry. Failure to
immediately leave the area may result in
serious injury or death.