Tan Delta vs. Other Technologies

By far the most common method used by these sensors is the measurement of the dielectric constant of the oil, the theory being that as the oil degrades the capacitance decreases.


However, all of these types of sensors suffer from the same issues:-

  1. Lack of sensitivity – Capacitance alone is not a good measure of overall oil condition.

  2. Temperature instability – As the dielectric constant of an oil also changes with temperature, it is difficult to see any actual oil changes.

  3. Lack of repeatability – Due to the above.

Some manufacturers have therefore taken the approach to combine various measuring techniques in the same sensor such as:-

  1. Dielectric Constant

  2. Moisture

  3. Viscosity

  4. Temperature

  5. Relative Humidity


These sensors then give multiple outputs and either by customer analysis and/or expert system attempt to establish the overall oil condition. This tends to be very confusing and still suffers from the limitations listed above.

More recently variou

s new methods and technologies have been applied, these include the use of tuning fork technology, complex dielectric and FTIR (Fourier Transform Infrared Spectroscopy). Other than the tuning fork which has very limited capability, the new technologies do offer a limited level of sensitivity but the interpretation of the output is complex, problematic and can suffer from the same limitations listed above.

The Tan Delta Oil Quality Sensor (OQSx), uses a patented method accurately measuring the electro-chemical properties of the oil at a molecular level. This is achieved by using a very high frequency AC current to accurately measure the ratio between conductance and capacitance of the oil, giving an extremely high level of sensitivity to all common oil wear mechanisms and contaminations with exceptional temperature stability and repeatability.


The sensor is configured with the electro-chemical fingerprint for the required oil, as the oil changes (for example with oxidisation, additive depletion, contamination and/or viscosity change), the electro-chemical fingerprint of the oil also changes and these minute differences are detected by the OQSx.


Repeated independent testing has established the point at which this increased molecular activity (regardless of the cause) will have a detrimental effect on the oils ability to lubricate.


This gives the OQSx the ability to monitor an oil through its whole lifecycle from brand new to End of Life, giving you an accurate oil condition by constantly measuring the difference between the clean oil and the current live oil, giving a simple traffic light output with an index to enable complete trending of the oil condition over time.




Posted on 07 Aug 2017

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