Oil quality monitoring

Oil quality monitoring

Oil condition monitoring supports maintenance in hydraulic systems, industrial gearboxes and lubrication circuits. Depending on the instrument, oil moisture sensors measure relative humidity and temperature, while multiparameter sensors also track relative dielectric permittivity or electrical conductivity. Changes are interpreted against the oil type, operating conditions and reference values.

For water-in-oil monitoring, relative humidity indicates the degree of water saturation at the measurement temperature; it is not a percentage of water by volume. Water content in ppm is available only where supported by the model and suitable oil-specific calibration data. Oil particle counters provide separate information about particulate contamination and cleanliness, for example as ISO 4406 codes. They serve a different purpose from moisture sensors.

Some instruments combine oil condition parameters with level measurement. Specify the required measurements, oil type, additives, viscosity, pressure, temperature, flow through the measuring point and mounting arrangement, together with a 4–20 mA output or communication such as RS232, CANopen or SAE J1939. Parameter combinations and interfaces are checked for the selected model. Online trends complement laboratory oil analysis.