Carbon Monoxide Alarm User Manual

Page 13
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 MODE button allows the user to toggle
between available meter display screens. Several
additional screens are available to the user in the
Technician mode.
The first screen is the gas level display discussed above.
Pressing the MODE button once displays the peak
readings of the gases being measured during the current
monitoring interval.
The instrument will automatically cycle between two peak
reading screens, one for oxygen, and one for the other
gases being measured. The oxygen peak reading screen
shows both the high (HI) and low (LO) readings.
Pressing the MODE button again displays the STEL
(Short Term Exposure Levels) of the toxic gases being
measured. Since STEL calculations are made using the
most recent fifteen-minute monitoring interval, it is not
possible to compute a toxic gas STEL until the PhD
2
has
been monitoring for at least fifteen minutes. Until the
minimum monitoring time has elapsed, the STEL screen
will show an "X" where the reading should be.
Anytime after the first fifteen minutes have elapsed, the
STEL screen will show the appropriate numerical value.
Pressing the MODE button again displays TWA (Time
Weighted Average) exposure levels. TWA values are
calculated by projecting exposures over an eight hour
period. It is not possible to compute a toxic gas TWA
until the PhD
2
has been monitoring for at least one hour.
Until the minimum monitoring time has elapsed, the TWA
screen will show an "X" where the reading should be. The
screen also indicates how many completed (full) hours
the instrument has been on. (If the PhD
2
has been on for
less than one full hour the screen indicates "0" completed
hours.)
Pressing the MODE button again displays the final screen
showing 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.
2.2.4 Changing operating modes
It is possible to shift from one operating mode to another
while the instrument is in use without the loss of data. It
is not necessary to turn the instrument off before
switching. Simply remove the keypad cover to expose
the four mini-push-buttons, and simultaneously push the
"+" and "-" buttons to change operating modes. Each
time the operating mode is changed the display screen
will briefly indicate which operating mode has been
selected.
Shifting modes or otherwise reprogramming the
instrument should only be done by employees who
are authorized to do so.
2.3 Batteries
2.3.1 PhD
2
battery options
Two types of rechargeable batteries are available for use
in the PhD
2
design. The type of battery selected must be
specified at the time of purchase.
2.3.1.1 NiCad
A removable NiCad battery pack is available as an option
with the PhD
2
design. The NiCad battery pack is secured
by two screws located on the bottom of the PhD
2
case,
and may be removed or replaced without disassembly of
the instrument. The NiCad battery pack may be safely
removed and replaced even while the PhD
2
is being used
in hazardous locations.
CAUTION: Make sure the PhD
2
is turned off before
removing the NiCad pack! Removing the NiCad pack
before the instrument has properly stored the current
data during shut-down may result in the loss of data
from the most recent monitoring session.
CAUTION: If the NiCad battery pack is removed it
must be replaced within one hour to avoid the
potential loss of recorded gas measurement data.
(Calibration and configuration data are stored in a
non-volatile permanent memory, and are not subject
to loss due to battery removal.)
CAUTION: Care should be taken not to over tighten
the screws which secure the NiCad battery pack into