Carbon Monoxide Alarm User Manual

Page 12
2.2.1 Text Only mode
The simplest mode of operation is the "Text Only" mode.
In this mode, during normal operation, the LCD screen
does not display numerical readings, only the indication
"OK."
If an alarm condition occurs, that is, when one of the
sensor readings exceeds a pre-set alarm level, the
indication changes from "OK" to the numerical value, the
LED alarm light flashes, and the audible alarm sounds.
PhD
2
alarms are normally self-resetting. When readings
drop back below the pre-set alarm levels, the screen
reverts back to the "OK" indication, and visual and
audible alarms cease.
In the Text Only mode, only one push-button is used to
turn the instrument on and off, and to switch screens.
Pressing the large black MODE button allows the user to
toggle between available meter display "screens." Two
screens are available to the user in the "Text Only" mode.
The first screen is the gas level display discussed above.
Pressing the MODE button displays the second screen,
which shows battery voltage, running time for the
instrument, and temperature.
Pressing the MODE button again toggles the display back
to the first screen showing current gas levels.
2.2.2 Basic mode
The "Basic" mode of operation is designed for users with
a higher level of understanding, and a need for numerical
readings, but who are not experts in gas detection.
In the Basic mode, as in the Text Only mode, the user
has access to only two "screens" of information. In both
the Text Only and Basic modes, only one push-button
(the MODE button) is used to turn the instrument on and
off, and to switch screens. The major difference between
the two modes is that in the Basic mode numerical gas
level readings are provided, whereas in the Text Only
mode only an indication that conditions are "OK" is
provided during normal operation. Another important
difference is that it is possible to do a fresh air calibration
adjustment while in the Basic mode. This feature is not
enabled when the instrument is operated in the Text Only
mode. (Calibration procedures are discussed in
detail in Chapter 3.)
Basic mode current gas level screen:
If an alarm condition occurs, that is, when one of the
sensor readings exceeds a pre-set alarm level, the
numerical reading changes to reflect the new value, the
LED alarm light flashes, and the audible alarm sounds.
PhD
2
alarms are normally self-resetting. When readings
drop back below the pre-set alarm levels, visual and
audible alarms cease, and normal operation of the
instrument resumes.
Pressing the large black MODE button allows the user to
toggle between available meter display screens.
Two screens are available to the user in Basic mode.
The first screen is the gas level display discussed above.
Pressing the MODE button displays the second screen,
which shows clock time, number of data points saved,
temperature, run time, and battery voltage.
Pressing the MODE button again toggles the display back
to the first screen showing current gas levels.
No matter which mode is selected, anytime the PhD
2
is
on it is remembering the peak readings of all gases
measured, and is calculating both long term Time
Weighted Averages and Short Term Exposure Levels for
the toxic gases, and will go into alarm whenever
appropriate
2.2.3 Technician mode
The "Technician Mode" provides access to all advanced
functions and displays. Although it is possible to make a
fresh air "zero" adjustment while in the Basic mode, it is
necessary to be in the Technician Mode before beginning
the "span" calibration procedure or making use of other
advanced PhD
2
functions.
Calibration procedures are discussed in detail in
Chapter 3.
After the completion of the start-up and self-test
sequence, the meter display will show numeric readings
of the gases being measured.
If an alarm condition occurs, that is, when one of the
sensor readings exceeds a pre-set alarm level, the
numerical reading changes to reflect the new value, the
LED alarm light flashes, and the audible alarm sounds.