Det-Tronics SW9200x Slickwatch IR Oil Detection System - Manual (Page 12)

INSTRUMENT OUTPUT
The 0-10 VDC RATIO output is available on all SW9200
instruments at the RATIO (brown) test jack on the front
panel, and at terminal 1 of the receiver junction box
when the OUTPUT SELECT switch is set to position V
(volts). When viewing an oil film using the standard 0-10
VDC output, the RATIO output will vary according to the
type and severity of the oil spill. The output does not
increase linearly with film thickness. Generally, a thin
film of oil will give a RATIO output between +1.5 and +10
VDC, with wide fluctuations due to irregularities in the
film. Thicker oil films (greater than 10 um average thick-
ness) tend to produce a steady RATIO output between
+3.0 and +7.0 VDC.
An optional Film Thickness Discriminator can be ordered
with the instrument. Located on the Options p.c. board,
this option converts the standard 0 to 10 VDC RATIO
output to a “high” -”low” output. With the Film Thickness
Discriminator option, the OUTPUT SELECT switch on the
front panel must be set on the O position (options).
When a “thin” film (less than 10 micrometers) is
observed, the RATIO output will be a positive voltage
(approximately +1.0 VDC). When a “thick” film (greater
than 10 micrometers) is observed, the RATIO output will
be a negative voltage (approximately -15.0 VDC).
The Selectable Criteria Alarm option, located on the
Options p.c. board, delays the activation of the oil alarm
relay until either of two selectable conditions are met.
NOTE
If either the Film Thickness Discriminator or
Selectable Criteria Alarm Option has been pur-
chased with the SW9200, additional information will
be found in the APPENDIX.
An optional 4-20 mA output can be ordered with the
instrument or can be field installed at any time after pur-
chase. The 4-20 mA output option, located on the
Options p.c. board, converts the standard RATIO output
from 0 to 10 VDC to 4-20 mA. If installed, the 4-20 mA
output will be available at terminal 1 of the receiver junc-
tion box when the OUTPUT SELECT switch on the front
panel is set to the mA position. The 4-20 mA current can
be tested by removing the RATIO wire in the junction
box and connecting a current meter between the RATIO
wire and terminal 1. The 4-20 mA output will drive a
user-supplied load of 0 to 500 ohms. The 4-20 mA out-
put is surge protected by transient protection devices.
NOTE
The Film Thickness Discriminator, the Selectable
Criteria Alarm and the 4-20 mA Output options can-
not be used in combination in the SW9200.
The RATIO output in this manual is indicated in 0-10
VDC. For instruments using the 4-20 mA output, the
standard 0-10 VDC output can be read at the RATIO test
jack (brown) on the front panel or at the receiver junction
box when the OUTPUT SELECT switch is set to the V
position. In addition, a voltage to current transfer curve
is provided in the APPENDIX.
Outputs should be monitored as required by the particu-
lar application. When the instrument views clean water,
the RATIO voltage will be between 0.5 and +1.5 VDC.
The voltage levels at the outputs of the NUMERATOR
and DENOMINATOR will vary according to the water
surface condition.
If the above mentioned indications do not occur, or in
the event of a prolonged instrument status alarm, consult
the Troubleshooting Table.
OIL ALARM THRESHOLD ADJUST-
MENT
Based on the specific application of the instrument,
select the RATIO voltage threshold at which the Oil
Alarm will activate. The Oil Alarm is factory set at +2.0
VDC. To test the SW9200’s sensitivity to oil films, allow it
to view clean water and then add a small quantity of oil
to the water, either in a test pan or on the water surface
being monitored. Appropriate containment and cleanup
procedures must be carefully followed to avoid violation
of Federal, state or local regulations. If the oil alarm acti-
vates at a smaller quantity of oil than required by the
instrument’s application, instrument sensitivity may be
slightly decreased (or increased) by the following proce-
dure:
1. Attach a digital voltmeter between the OIL ALARM
SETPOINT jack (grey) and SIG. GND. (green) on the
front panel.
2. Adjust the OIL ALARM ADJUST potentiometer on
the front panel so that the Oil Alarm set point voltage
is slightly lower than the desired RATIO output.
NOTE
The oil alarm threshold adjustment is disabled
when the Film Thickness Discriminator optional p.c.
board is used.
The oil alarm threshold adjustment provides the
definition of “oil observation” for the Selectable
Criteria Alarm Option. See the APPENDIX for infor-
mation on the alarm criteria settings for this option,
if installed.
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