Patent ID: 6891383

Claim:
A method for detecting a concentration of soot particles in engine oil comprising the steps of: applying a microwave signal having a frequency to one end of a transmission line having a probe tip at a second end of the transmission line and varying the frequency of the microwave signal within a range of frequencies, the probe tip being exposed to the engine oil; detecting a probe voltage at a stationary detection point along an axial length of the transmission line for selected frequencies within the range of frequencies; determining a probe frequency of the selected frequencies when the probe voltage is equal to a null voltage of a standing wave within the transmission line; comparing the probe frequency to a probe reference frequency, wherein the probe reference frequency is a frequency of the microwave signal when the probe voltage is equal to a null voltage for a known concentration of soot particles in the engine oil; and calculating the concentration of soot particles in the engine oil based upon a result of the comparing step.