8
audible and visible alarms will continue to sound even
after the atmospheric hazard has cleared. To turn the
alarm off, simply press the MODE button. If the PhD Lite’s
alarm latch is disabled and the alarm condition is no
longer present, the instrument will automatically return to
normal operation, and the visible and audible alarms will
cease without further input from the user.
The procedure for changing alarm and OK latch
settings is covered in section 3.2.3.
1.5.2 Atmospheric hazard alarms
The PhD Lite portable gas
detector has been designed for the detection of
deficiencies of oxygen, accumulations of flammable
gases and vapors, and accumulations of toxic vapors.
An alarm condition indicating the presence of one or
more of these potentially life-threatening hazards
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.
A rapid up-scale reading followed
by a declining or erratic reading may indicate a
hazardous combustible gas concentration that
exceeds the PhD Lite’s zero to 100 percent LEL
detection range.
The combustible gas alarm is activated when the percent
LEL (Lower Explosive Limit) gas concentration exceeds
the pre-set alarm point.
Two oxygen alarm set points have been provided; one for
low concentrations associated with oxygen deficiencies
and one for high concentrations associated with oxygen
enrichments.
Three alarm set points have been provided for each toxic
gas that is monitored: TWA (Time Weighted Average),
STEL (Short Term Exposure Limit), and Ceiling.
Appendix A discusses alarm levels and factory default
alarm settings.
The procedure for adjusting alarm settings is covered
in section 3.2.2.
1.5.3 Sensor overrange alarms.
The PhD Lite toxic gas channel will go into alarm if a
sensor is exposed to a concentration of gas that exceeds
its established range. If the peak alarm is enabled it will
go off before an overrange alarm provided a STEL or TWA
alarm is not activated first. If the peak alarm is disabled
and a toxic sensor goes into overrange alarm a “SENSOR
OUT OF RANGE” message will appear at the bottom of
the display while the audible and visible are activated.
The maximum range value will be displayed for the sensor
in alarm. If the LEL sensor goes into overrange alarm, the
message “LEL OVERRANGE” will intermittently appear,
both the audible alarm and the flashing LED alarms will be
activated and an “X” will appear on the LCD in the place
of the numeric reading for the LEL sensor.
In the event of an LEL overrange
alarm the PhD Lite must be turned off, brought to an
area that is known to be safe and then turned on
again to reset the alarm.
Note: The PhD Lite features automatic warning
against LEL sensor response failure due to lack of
oxygen. When oxygen levels fall below 10% of gross
volume, the PhD Lite will intermittently display a
message indicating that O
2
is too low for LEL to
operate.
1.5.4 Low battery alarms
Note: The voltage figures given below are for PhD
Lite instruments with firmware version 3.18 and may
be slightly different for units with other versions of
instrument firmware.
The PhD Lite 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 is reduced to approximately 3.23 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 3.13 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 to 3.10 volts, the PhD Lite will
display a "Dead Battery" message to warn the user of
imminent shut down. The instrument will then
automatically turn itself off.
After any low battery alarm the batteries should be
replaced if the PhD Lite is equipped with alkaline
batteries or the battery should be recharged if the PhD
Lite is equipped with a NiMH rechargeable battery.
The PhD Lite must be located in a
non-hazardous location whenever the alkaline
batteries are removed from the instrument.
Removing the alkaline batteries from the instrument
in a hazardous location may impair intrinsic safety.
Use only Duracell MN1500 or
Ultra MX1500, Eveready Energizer E91-LR6, Eveready
EN91, Radio Shack 23-874 (not ATEX approved) size
AA 1.5V Alkaline batteries, Eveready CH15 (not ATEX
approved) or Radio Shack 23-149 (not ATEX
approved) size AA 1.2V NiCad batteries, or Eveready
L91 size AA 1.5V Lithium batteries (not CSA or ATEX
approved). Substitution of batteries may impair
intrinsic safety.
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