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3. Principle of operation
3.1 Measuring Principle
An optical sensor array measures a combination of light scattered and absorbed by oil
droplets in the sample stream. The sensor signals are processed by a microprocessor to
produce linearized output.
If an alarm (set point form 1 ppm to 15 ppm) occurs, the two oil alarm relays are activated
after the adjusted time delay.
The microprocessor continuously monitors the condition of the sensor components and
associated electronics to ensure that calibration accuracy is maintained over time and
extremes of environmental conditions.
3.2 Display Visualization
The display visualizes the oil content status of the units. Using the buttons, it is also
possible to see information about the settings.
3.3 Alarms
The units contain two independent oil alarm circuits. From the manufacturing both alarms
are set to 15 ppm (according IMO). The set points can be changed according to the
requirements on site, to any point between 1 ppm and 15 ppm. An alarm point setting
above 15 ppm is not possible. The adjustment can be done in the programming mode as
described in the appendix (See section 21.2.3 Functional Buttons AL1/ AL2/ SET).
Both alarm circuits are also related to an alarm LED on the front panel.
Additional to the alarm LEDs each alarm circuit is equipped with a relay with potential
free alarm contacts. These contacts can be used for external processing of the signal or
for control of further functions. The alarm circuits contain two independent alarm delays,
which can be set separately.
In case of malfunction the “SYS LED” will indicate some type of internal fault of the unit.
This LED is flashing green in normal conditions and is red in alarm conditions.
If a malfunction or failure of the power supply occurs, relays (both alarm relays) will switch
to alarm condition. (See Section 22. Appendix III. for an easily understandable example).
If the unit is off, both relays will be in alarm condition.
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