Introduction
The condition of oil and lubricants as they are used in engines and other important assets is becoming increasingly important as environmental concerns and economic constraints driven by fuel and lubricant prices are forcing manufacturers and consumers to optimize engine and equipment performance. Research on the properties of oil has revealed the following metrics to be leading indicators of oil quality:

• Viscosity
• Conductivity
• Dielectric Constant
• Water Content
• Soot Content
• Base Number
• Acid Number
• Particulate Count

Monitoring these metrics in real time has proven to be a cost effective means of preventing serious engine and equipment damage. Most of these measurements have had to be performed in the laboratory, a time consuming and often costly endeavor. With the advent of new sensing technologies, it is now possible to measure some of these metrics on-site and in real time. Of these metrics, viscosity, conductivity and the dielectric constant are the most readily amenable to being monitored by sensors.

Viscosity
One of the most important reasons to monitor the viscosity of oils is to detect fuel dilution, and as a parameter for the determination of the useful oil-life remaining. The leakage of fuel into an oil bearing cavity dramatically reduced the viscosity of the oil and therefore monitoring oil viscosity is an effective way to prevent continued fuel dilution. However, other factors such as fuel soot levels and oil oxidation can cancel this effect by increasing the viscosity of oil. And, therefore, it is equally important to measure other metrics, including the dielectric constant and the conductivity of the oil to provide an effective oil quality monitoring regime.

Dielectric Constant
The dielectric constant of a material is a measure of its ability to transmit electrical potential energy. The presence of charge carrying ions increases the dielectric constant of fluids. For example, the dielectric constants of oils range between the 2.0 to 5.0, while the dielectric constant of water is around the 70.0 mark. And therefore, the presence of water in oil can quickly be determined by measuring the dielectric constant of oil over time. A sudden spike is very indicative of the presence of water. However, water alone does not engender this result. An increased number of carbon ions can also dramatically increase the dielectric constant of oil. Soot concentration levels can therefore also be derived from the dielectric constant of oil.

Conductivity
Similar to the dielectric constant, conductivity is another important metric when it comes to determining oil quality. The conductivity of oil is dramatically impacted by the presence of particulate matter and water. The conductivity of oil increases with the presence of water, soot and metal particles within the oil. As can be surmised, none of these three metrics by themselves provides a definitive indication of oil quality, however, when combined the three metrics can yield to very wholesome estimates of oil quality. Algorithms that prioritize and combine these three metrics can yield single measure metrics, which, when interpreted correctly can provide actionable and reliable data with regards to oil quality.

What SenGenuity Offers Today
SenGenuity is the only major provider of SAW based Viscosity Sensors in the market. These sensors have been used in a wide range of oil based applications in both the fixed asset and mobile asset segments. The sensors provide exceptional on-site and real time viscosity trending capabilities. Their solid-state, plug-and-play capabilities make them ideal for process and automotive applications. The sensors are, at present, being evaluated by major manufacturers of diesel engines. However, as indicated earlier, while viscosity is extremely important, it is equally important to monitor the dielectric constant and conductivity of oils for mobile asset applications. SenGenuity intends on launching a combined conductivity and dielectric sensor in 2010 and intends to combine viscosity, conductivity, dielectric and temperature sensor monitoring by 2010 for the fluid condition sensor (FCS) platform. Please contact Kerem Durdag, Director of Sales and Marketing at 1-603-578-4066 or e-mail at sensors@sengenuity.com for related inquiries.