Carbon Monoxide Alarm User Manual

Page 26
5.3.3 Configuring toxic gas channels
There are two toxic channels in the PhD
2
design. They
are designated "Toxic 1" and "Toxic 2." Pressing the Cal
button will advance to the first toxic channel set-up
screen.
Besides identifying which Toxic channel is currently being
configured, the screen also identifies which type of sensor
has been selected. In the screen example above, "CO"
indicates a carbon monoxide sensor has been selected.
It is possible to use the "+" and "-" keys to scroll through
the current toxic sensor menu list.
CAUTION: If a new toxic sensor type is selected
verify that it has been properly installed in the correct
toxic sensor socket. Calibrate the new sensor before
use.
Highly reactive or "corrosive" gases such as ammonia,
chlorine, hydrogen cyanide, and hydrogen chloride tend
to react quickly with or be absorbed by other substances.
These reactions can occur so quickly that there may not
be adequate time for the gases to diffuse through the
moisture barrier in the standard PhD
2
sensor
compartment cover before they are gone.
The standard sensor
compartment cover (which includes a moisture
barrier) may not be used as long as a corrosive gas
sensor is installed. When the sensors installed in
your PhD
2
include a corrosive gas sensor, a special
sensor compartment cover (part number 35-692)
must also be installed.
Please be advised that the sensor compartment
cover used when a chlorine, ammonia, hydrogen
cyanide, hydrogen chloride, or TOX 1 sensor is
installed does not include a moisture barrier filter.
Avoid direct exposure to liquids to reduce the chance
for damage due to leakage.
The standard sensor compartment cover (which
includes a moisture barrier) may not be used as long
as a corrosive gas sensor is installed.
TOX
2
TOX
1
L.E.L.
O2
Figure 5.1: Placement of PhD
2
sensors in the sensor
compartment
If a sensor is not installed in Toxic 1 or Toxic 2, or if a
toxic sensor is to be permanently removed, use the "+"
and "-" keys to choose the "Disable" option from the toxic
sensor menu list.
5.3.3.1 Resetting the toxic sensor bias
voltage
Most of the toxic sensors available for use in the PhD
2
are "unbiased," that is, they do not require a constant
voltage applied to them while the instrument is turned off.
Four currently available toxic sensors do require a bias
voltage. The bias must be set at the time they are
installed The four sensors are nitric oxide (NO),
hydrogen chloride (HCl), ammonia (NH3), and the "TOX
1" broad range electrochemical sensor.
When a toxic sensor channel is being reconfigured
from one unbiased sensor type to another unbiased
sensor it is not necessary to adjust the bias voltage.
The bias voltage for all unbiased toxic sensors
should be set at 0.0 mV.
It will be necessary to readjust the bias voltage
whenever the new toxic sensor has a different bias
voltage than the old one.
Resetting the toxic sensor bias voltage requires
opening the instrument and adjusting a
potentiometer located on the main circuit board of
the detector. This procedure should not be done by
unauthorized persons. In many cases it may be
better to return the detector to the factory for
adjustment.
Biased type toxic sensors may only be installed in
Toxic Channel 1.
The following table lists currently available toxic sensors,
and their appropriate bias voltages.