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3.1
REMOTE CALIBRATION OPTION
In most applications, it is recommended to install the
PointWatch Eclipse CO
2
model where it will contact the
gas of interest as quickly as possible. Unfortunately,
the best location for early warning can often result in
accessibility problems for the operator when calibration
is required. In these applications, the Model PIRTB
Termination Box is highly recommended to provide the
ability to calibrate the detector from a remote location.
The PIRTB consists of a termination/circuit board, housed
within an explosion-proof junction box. The circuit board
contains a magnetic reed switch for initiating calibration,
an indicating LED to signal the operator when to apply
and remove the calibration gas, and a wiring terminal
block. A version of the junction box is furnished with
a small viewing window that enables calibration to be
performed without hazardous area de-classification.
The PIRTB may be installed up to 100 feet away from
the Eclipse. Refer to Figure 16 for remote calibration
configuration options.
NOTE
The remote calibration switch is intended for
initiating calibration only. Resetting latching alarm
outputs using the remote calibration switch cannot
be accomplished without entering the Calibration
mode.
The following recommendations are provided to enhance
operator ease and convenience of remote calibration
configurations:
1. Install the Eclipse in such a manner that the onboard
LED is visible whenever possible. This will aid in
checking device status "at a glance."
2. The Eclipse is provided with a calibration gas nozzle
on the weather baffle, which allows the use of
permanently attached calibration gas delivery tubing
(either polyethylene or stainless steel). The tubing is
typically routed in parallel with the remote calibration
cabling to the same location as the PIRTB termination
box. This arrangement enables a technician to
initiate calibration and deliver the calibration gas to
the Eclipse from a single location.
3. When permanently installed calibration gas tubing
is utilized, always install a shut-off valve at the open
end to prevent unwanted gas or debris from entering
the tubing.
4. Always purge the permanent tubing with pure
nitrogen prior to and immediately after calibration
to ensure that residual carbon dioxide gases are
cleared. Always close the shutoff valve after post-
calibration purging is complete. This will ensure
that all the carbon dioxide gas is eliminated from the
Eclipse optics.
5. Note that permanently installed calibration gas
tubing will increase the calibration gas consumption
rate as a function of total tubing length.
Other methods of remote Eclipse calibration include
utilizing HART or MODBUS communications. Refer to
the HART and MODBUS appendices for details.
