Det-Tronics SW9200x Slickwatch IR Oil Detection System - Manual (Page 10)

OPTICAL ALIGNMENT
Accurate alignment is generally not critical when the
water surface is turbulent, but it is quite critical when the
water surface is calm. For this reason, alignment should
be accomplished when the water surface is calm to
allow for the worst-case situation. If the water surface to
be monitored is affected by tides or storm flood varia-
tions, these steps should be followed at mid-tide or the
usual water level.
While alignment is time-consuming, it can be reassuring
to note that it should not be necessary to repeat this pro-
cedure for the duration of the instrument’s use at a par-
ticular site. Once the correct alignment has been
achieved, the housings will be locked in position and
removal of the cover or window assemblies for servicing
should not affect the alignment of the instrument.
1. Use shims to “toe in” the transmitter and receiver so
that both appear to be aimed at approximately the
same point on the water surface directly below the
instrument, as shown in Figure 8.
2. Using the test jacks on the front panel, connect a
digital voltmeter (with a resolution of at least 1 milli-
volt DC) between the NUMERATOR output (blue)
and SIGNAL GROUND (green).
NOTE
All voltage readings must be taken using a DC volt-
meter with a 10 Megohm input impedance. Use of
other devices will give inaccurate readings.
3. Change the transmitter angle slightly and note the
change in the voltage observed in Step 3. If the
voltage decreases, change the angle in the opposite
direction to increase the NUMERATOR voltage.
9 95-8409
HEIGHT ABOVE WATER
SEPARATING DISTANCE
θ θ
A1455
Figure 8—Alignment of Transmitter and Receiver
Assuming Assuming
14.5 Inches 368.3 Millimeters
Height Diameter Separation Angle Separation Angle Shim Thickness
Above Water Monitored From Vertical From Vertical Under Box
(Feet) (Meters) (Inches) (Millmeters) (Degrees) (Degrees) (Inches) (Millimeters)
5 1.52 3.00 76.20 6.89 21.63 0.544 13.811
10 3.05 6.00 152.40 3.46 11.21 0.272 6.906
15 4.57 9.00 228.60 2.31 7.53 0.181 4.604
20 6.10 12.00 304.80 1.73 5.66 0.136 3.453
25 7.62 15.00 381.00 1.38 4.53 0.109 2.762
30 9.14 18.00 457.20 1.15 3.78 0.091 2.302
Figure 7—System Interwiring Diagram