SMART WiO – Water in Oil Sensor

The SMART WIO is a water in oil sensor measuring the humidity providing a key indicator of oil quality.


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.

  • Condition monitoring Lubrication oil including:
    • 2 and 4 stroke engines
    • Compressors
    • Pumps
    • Gear boxes
    • Turbines
  • Condition monitoring for Hydraulic oil including;
  • All machines using hydraulic oil up to 10bar
  • Measures the absolute water content in oil.
  • Early warning by using pre alarm and alarm
    • The PAV (Pre Alarm Value) is set to 50% humidity.
    • The MAV (Main Alarm Value) is set to 90%
  • Takes the oil temperature into consideration in order to measure the saturation
  • The sensor measures the saturation of the oil independent from the oil type and oil age
  • No cleaning of the sensor is needed.
20181016 150240 2
20181016 150240 2
FRG00035 xx reduziert scaled
FRG00035 xx reduziert scaled
20181016 150247
20181016 150247


Power Supply 18…32 VDC
Current Consumption 60mA
Polarity Protection Yes
Alarm relays Pre-alarm at 50% humidity
Main alarm at 90% humidity
Output Current <300mA
Operating Temperature -25 to +85 0C
Protection Degree IP67
Analog Output: Water in Oil 4…20 mA (equiv. 0…100% Humidity Linear)
Analog Output: Temperature 4…20 mA (equiv. 0…1000C Linear)
Dimensions: 125mm x 80mm x 57mm
Local Indication LED Indicators
Sensor Probe Specification  
Wrong Polarity Protection Yes
Operating temperature -25 to 85 deg C
Protection degree IP65
Pressure resistance against medium 10 bar
Connection type G3/4” Male Thread
Material Stainless Steel AISI 303; 1.4305
Dimensions 50mm x 187mm
Cable Length to Controller 15m
Insertion Length 120mm
Local indication LED Indicators


Indicator Dial Temperature   Indicator Dial Humidity  
Indicator Dial type Analog needle type Indicator Dial type Analog needle type
Unit of Measurement Degrees Celsius Unit of Measurement % Humidity
Range 0 – 1000C Range 0% – 100% Humidity
Dimensions 96mm x 96mm x 77mm Dimensions 96mm x 96mm x 77mm


Specifications and system descriptions accurate at time of publishing. These are subject to change.