4.1 Laboratory Calibration Procedure
Calibration is carried out on the main board of PS-220 inside the open enclosure.
All voltages measured in PS-220 board are DC.
The negative probe of voltmeter is connected to TP2 (GND).
NOTE: TP3 and TP4 measure the same signal, but TP4 is located after an
additional buffer. It is better to measure at TP4.
4.1.1 Sensor in the Air
Measure and set the voltage at TP3 to 0.01 ÷ 0.03V using potentiometer
R3.
Approach this value from the direction of a higher voltage only. Stop tuning
immediately when the goal is achieved.
4.1.2 Sensor in Test Water (no Oil)
• If water is normally contaminated with a layer of oil, dip the sensor in oil. Take
the sensor assembly out of oil, and let oil trickle down for 15-20 sec.
• Put the sensor in water (without cleaning), and let it float freely. Secure cable
at the top of the vessel.
• Wait a few seconds, then measure and set the voltage at TP3 to 3.50V
using R5.
(For some demo units only: R5 is the calibration screw next to
WATER light on the front panel).
• Measure the voltage at TP1 and set it to 3.40V using
potentiometer R1.
The difference between the voltages at TP3 and TP1 determines the
minimum oil thickness detected. A difference of 0.1V (3.50 – 3.40) is the
most recommended sensitive setting.
4.1.3 Oil Layer Detection
• Add a 2mm layer of the oil to be detected to the water.
OIL light should turn on.
If OIL light is on, turn R1 counter-clockwise till WATER light turns on, then
clockwise till OIL just turns on.
Otherwise, if OIL light off, turn R1 clockwise until it turns on.
• If a layer other than 2mm should be detected, add the required oil
layer.
Turn potentiometer R1 clockwise (for layer less than 2mm) or counter-
clockwise (for layer more than 2mm) till the point where OIL light just turns
on and WATER light turns off.
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