Det-Tronics OPECL Infrared Hydrocarbon Gas Detector - Manual (Page 24)

22 95-8556 10.1
C. If adjustments to the receiver were necessary,
perform a zero calibration and then repeat the
sequence of partial beam blocks. Repeat the
adjust, zero calibration, and recheck process until
no adjustments to the receiver are necessary, and
the partial beam block has little or no effect on the
receiver under test.
10. With the beam block tool removed, the Ratio reading
must be between 0.65 and 0.95. If a reading over
1.0 is indicated, check to make sure that no other
transmitters, IR sources, or potential reflections are
within view of the receiver. It is possible for multiple
transmitters to be viewed by a single receiver.
Although each receiver is electronically synchronized
to its transmitter, zero drift and/or false gas readings
are possible if the rogue IR source continues in the
event of a beam block on the primary transmitter.
If this situation occurs, a ratio of over 1.0 will be
realized. Det-Tronics recommends eliminating any
condition that causes a receiver to display a ratio of
over 1.0.
11. When correct alignment is achieved, tighten all
mounting bolts to 20 lb-ft minimum using care not
to disturb the alignment. The telescope can be
used during this step to give a visual indication to
judge the effects of the tightening process on the
alignment. Check the alignment one final time using
the beam block tool to verify that the alignment did
not change as a result of tightening. If necessary,
fine tune the alignment.
12. Upon completion, the OPECL receiver should
produce a 4 mA output signal and a green LED
indication. If not, ensure that the device has been
zero calibrated.
13. Proper operation can be confirmed by bypassing
all system alarms, then placing an optical test film
(sold separately) into the light beam and checking
for the appropriate signal output level on the HART
field communicator process menu screen. Test
Film p/n 007902-002 should produce an output of
0.5 to 1.1 LFL-Meters. Test Film p/n 007902-003
should produce an output of 1.5 to 2.1 LFL-Meters.
Alarm conditions, if present, should clear when the
test film is removed from the beam.
14. Confirm proper operation by completely blocking
the light beam with a solid object such as a piece of
cardboard until a beam block fault is generated.
15. Replace the HART port cover and the brow.
16. Restore all system alarms to normal operation.
gaIN lEvEl ChECK (Optional)
It is necessary to complete the alignment procedure
before checking the gain level. A handheld HART
communication device (or S3 Software for an EQP
system) is required to check the gain.
procedure
1. Connect the handheld HART communicator to the
receiver module’s onboard HART communication
port.
2. Turn on the HART communicator and check
for OPECL device recognition. When HART
communication is established, the OPGD Rx Root
menu will be displayed on the communicator display.
3. From the Root menu, select the Status Menu
(selection #2).
4. From the Status Menu, select the Sensor Information
Menu (selection #3).
5. The Sensor Information Menu will display the
following screen.
6. Observe the Gas Gain level indicated on the Sensor
Information Menu screen.
7. Table 4 can be used as a guideline for new
installations to assess Gas Gain level with proper
alignment.
1) Active XXX
2) Reference XXX
3) Ratio XXX
4) Gas Gain X
5) Absorption XXX
Gas Gain number
Table 4— Expected Gas Gain Settings for OPECL
Distance (m) gain Setting
5 1-3*
20 1*
40 1 - 2
60 2
80 2 - 3
100 3
120 3 - 4
*Use the Aperture Kit to get desired gain settings.