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1.6.3.1 Low battery alarm settings for NiCad
battery packs
The PhD Ultra includes low battery alarms that are
activated whenever battery voltage approaches a
level that will soon lead to instrument shut down.
When the battery voltage in NiCad-equipped
instruments is reduced to approximately 3.3 volts,
an audible alarm will sound and the display will
indicate that a low battery condition exists. At this
stage, the low battery alarms may be silenced for a
fifteen-minute period by pressing the MODE button.
After the first low battery alarm, the alarm will sound
again every fifteen minutes until the voltage drops
to the “Very Low Battery” level.
The “Very Low Battery” level occurs when the
battery voltage drops to 3.25 volts. Due to the risk
of imminent shut down, when the battery voltage
reaches the “Very Low Battery” level it is no longer
possible to silence the low battery alarms. At this
point, it is necessary to immediately leave the
hazardous area in which the instrument is being
used.
When the voltage drops below 3.25 volts, the PhD
Ultra will display a "Dead Battery" message to warn
the user of imminent shut down. The instrument will
then automatically turn itself off.
Following any low battery alarm the batteries should
be replaced if the PhD Ultra is equipped with
alkaline batteries or the battery should be recharged
if the PhD Ultra is equipped with a NiCad
rechargeable battery.
1.6.3.2 Low battery alarm settings for alkaline
battery packs
If the PhD Ultra has been equipped with a
disposable alkaline battery pack, the initial low
battery alarm will be activated when voltage is
reduced to 3.2 Volts. Protective shutdown occurs at
3.1 Volts.
Use only Duracell MN1500 or
Ultra MX1500, Eveready Energizer E91-LR6, or
Eveready EN91 size AA 1.5V Alkaline batteries.
Substitution of batteries may impair intrinsic
safety.
1.6.4 Other alarms and special
microprocessor features
PhD Ultra software includes a number of additional
alarms designed to safeguard proper use of the
instrument. When the PhD Ultra detects that an
electronic fault or failure condition has occurred the
proper audible and visual alarms will be activated
and an explanatory message will be displayed.
The PhD Ultra is designed to
detect potentially life threatening atmospheric
conditions. Any alarm condition should be
taken seriously. The safest course of action is
to immediately leave the affected area, and
return only after further testing determines that
the area is once again safe for entry
.
1.6.4.1 Combustible sensor “over-limit” alarm
latch
Protective software “latches” the combustible alarm
when the sensor is exposed to 100 % LEL
combustible gas. Under these conditions the
combustible gas reading will show an “X” to indicate
an over-limit condition. The current gas reading
display will alternate with a screen showing the
message “LEL sensor over limit”. The audible and
visual alarms will sound continuously until the
instrument is manually reset by turning it off, and
then turning the instrument back on in an area
where the air is known to be fresh.
The “over-limit” alarm condition is discussed in
detail in Chapter 3.
1.6.4.2 Missing sensor
The PhD Ultra continually monitors sensor status.
When the instrument recognizes that a sensor is
missing, the display will show “X” instead of the
normal gas reading, the audible alarm will sound
and the LED indicator for the affected sensor will be
activated. Alarms will be silenced when the sensor
is replaced.
1.6.4.3 “Needs Cal”
Whenever the instrument is turned on, the PhD
Ultra automatically determines and displays
readings for the sensors that are recognized by the
instrument. If changes have been made to the type
or number of sensors installed since the last time
the instrument was turned on, the audible alarm will
be activated and a “Needs Calibration” message will
be displayed. A message screen will indicate which
sensors must be calibrated before further use.
A sensor that cannot be
calibrated or is found to be out of tolerance
must be replaced immediately. An instrument
that fails calibration may not be used until
testing with known concentration test gas
determines that accuracy has been restored,
and the instrument is once again fit for use.
1.6.4.4 “Can’t ID sensor”
If the PhD Ultra is unable to read the EEPROM of a
smart sensor currently installed, or if a smart sensor
is removed while the instrument is turned off without
being replaced with another sensor, a “Can’t ID
Sensor” message will be displayed for the affected
sensor channel (e.g. toxic 1”). Press the mode
button to acknowledge the condition and the
instrument will proceed to operate with those
sensors that can be successfully read.
