Det-Tronics OPECL Infrared Hydrocarbon Gas Detector - Manual (Page 23)

21 95-8556 10.1
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If a HART handheld communicator is not available,
the alignment procedure can be performed in
a limited way by monitoring the 4‑20 mA output.
(This method is only partially effective due to the
deadband built into the 4‑20 mA output.) If the
partial beam blocks result in output deflection
greater than 4.00 mA +/‑ 0.1, alignment should be
adjusted to eliminate the deflection. The oPeCL’s
status LeD can also be observed. The LeD should
remain green with the beam block in any position.
5. 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.
6. From the Root Menu, select the Status Menu
(selection #2).
7. From the Status Menu, select the Sensor Information
Menu (selection #3).
8. The Sensor Information Menu will display the
following:
(Absorption and Ratio are the readings of interest
while performing the alignment procedure.)
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Make alignment adjustments in very small
increments. After an adjustment is made, wait for
at least 10 seconds for the output level to stabilize.
Continue making adjustments, if necessary, until
the correct level is achieved.
9. Observe the absorption reading while performing
the following steps:
A. Perform a series of partial beam blocks to half
of the receiver lens using the partial beam block
tool (009762-002). Block the top, right, bottom,
and left halves of the lens individually. Verify
that the Absorption level displayed on the HART
communicator is as close to zero as possible.
B. If an absorption reading greater than +/- 5% is
realized, fine adjustment is necessary to achieve
optimal alignment. See Figure 21.
BEAM BLOCK TOP
If this block causes Absorption to increase
> 5%, move receiver down.
BEAM BLOCK RIGHT
If this block causes Absorption to increase
> 5%, move receiver left.
BEAM BLOCK BOTTOM
If this block causes Absorption to increase
> 5%, move receiver up.
BEAM BLOCK LEFT
If this block causes Absorption to increase
> 5%, move receiver right.
Figure 21—OPECL Beam Block Diagram
1) Active XXX
2) Reference XXX
3) Ratio XXX
4) Gas Gain X
5) Absorption XXX
Ratio value
Absorption value