Det-Tronics PW9200x Pathwatch IR Gas Detection System - Manual (Page 13)

the reflection is visible in the receiver window
when standing at the transmitter.
8. Remove the window assembly and check the sig-
nal at the NUMERATOR test jack (blue) on the
digital voltmeter. If the signal is greater than 100
millivolts, proceed with fine alignment as
described in Step 10.
9. If the NUMERATOR signal is still less than 100
millivolts, gross alignment can be obtained by
scanning the receiver. Set the pan adjustment of
the receiver to one side as far as it will go by turn-
ing the pan knob fully clockwise. Beginning with
the tilt adjustment set as far up as it will go (tilt
knob fully clockwise). Slowly move the tilt of the
receiver down as far as it will go by turning the tilt
knob counterclockwise. Watch for a sharp
increase in the signal strength (greater than 50
mV on the digital voltmeter). Change the pan of
the receiver by moving the pan knob a quarter
turn clockwise. Slowly move the tilt from bottom
to top. Repeat this scanning procedure until the
digital voltmeter indicates a NUMERATOR signal
greater than 100 millivolts.
10. Make small adjustments in the receiver pan and
tilt to maximize the amplitude of the NUMERATOR
voltage.
11. Make small adjustments in the transmitter pan
and tilt to maximize the amplitude of the NUMER-
ATOR voltage at the receiver.
12. Move the high lead of the voltmeter to the RATIO
test jack (brown) on the front panel and read the
output voltage. The RATIO voltage should be 0.1
± 0.1 vdc. If the output is not within this range,
adjust the OUTPUT ZERO potentiometer on the
front panel to bring the voltage within the desired
range. Clockwise turns will increase and counter-
clockwise turns will decrease the RATIO output
voltage.
13. Replace the receiver window assembly and read
the NUMERATOR voltage at terminal 3 in the
junction box. The NUMERATOR output obtained
should be between 0.3 vdc and 0.5 vdc. If the
NUMERATOR output is within this range, proceed
to Step 15. If the NUMERATOR output obtained
exceeds 0.5 volts or is less than 0.3 volts after fol-
lowing all steps of the Optical Alignment/Signal
Strength procedure, the preamplifier gain must be
adjusted as described in Step 14.
14. To adjust the preamplifier gain, follow the Access
to Internal Components procedure (see
“Maintenance” section) and locate the preamplifi-
er P.C. board within the heat sink fins. The
preamplifier gain adjustment potentiometer is
located on the preamplifier P.C. board and can
be reached by inserting a screwdriver between
the fins from the bottom of the heat sink (as
viewed when the housing cover is open, but
attached to the housing by its hinges).
If the NUMERATOR output voltage is less than 0.3
vdc, turn the preamplifier gain potentiometer
clockwise. If the NUMERATOR output voltage is
greater than 0.5 vdc, turn the preamplifier gain
potentiometer counterclockwise.
15. Once optimum alignment has been obtained,
carefully adjust the locking knob assembly on the
back of each mount so that the end of the shaft
just makes contact with the back of the front
plate.
DO NOT over tighten the locking knob
assembly.
16. View the target attached to the transmitter mount
through the receiver alignment scope to verify
that the cross hairs are centered on the target. If
the cross hairs are not centered and optimum
alignment is verified, adjust the cross hairs to
center on the target using the adjustment knobs
provided on the scope. Replace the protective
end caps on the alignment scope.
17. Repeat Step 16 for the transmitter alignment
scope.
NOTE
Optimum alignment must be accurately main-
tained to ensure proper operation of the instru-
ment. Careful adjustment of the alignment scope
cross hairs will enable verification of alignment
accuracy.
18. Recheck that the NUMERATOR output has not
been affected by steps 15 through 17.
19. Remove the receiver window assembly and return
the MODE selector switch on the front panel to
the OPERATE position. Replace the window
assembly.
OPERATION/PERFORMANCE CHECK
NOTE
All voltage readings must be taken with a dc volt-
meter with a 10 megohm input impedence. Use
of other devices will give inaccurate readings.
Proper operation should be verified periodically by
performing the checks and tests described below:
11 95-8400