The working principle is a capacitive measurement operating on absorption of water in oil. The physical measured value is % Humidity. New oil has the ability to hold a certain amount of dissolved water. The maximum water amount oil can hold is called “saturation point”. Above the “saturation point” free water will fall out which can cause corrosion inside of the engine. The “saturation point” is influenced by temperature and other different factors like the composition of oil mineral or synthetic, formulation of additives and will change during the lifetime of the oil. The Water in Oil Sensor (WiO) is not measuring free water or emulsion, which is detectable by regular Water in Oil test kits, it measures the absolute water content in oil.
The PAV (Pre Alarm Value) is set to 50% humidity.
The MAV (Main Alarm Value) is set to 90% humidity.
More than 100% humidity means free water is present. From this point regular Water in Oil test kits begin to measure.
Normally in the field, the water in oil content is measured by a Water in Oil test kit. The results are mostly <0.02% (or 100.02% humidity), this value means free water content. If the WiO Sensor shows the main alarm, the value is higher than 90% humidity and damage could be caused to the engine if 100% humidity is reached.