Apparatus and method for sensing particle accumulation in a medium

A method for detecting a relative permittivity of a medium to determine a percentage content in the medium of particles having an electrical loss component, the method comprising:

• establishing a baseline voltage level when the percentage particle content of the medium is substantially zero, the baseline voltage level associated with a first standing wave at least a portion of which is passed within the medium;
• varying the frequency of a microwave source to generate a second standing wave at least a portion of which is passed within the medium such that a null condition of the second standing wave is placed proximate a detection point;
• determining a second voltage level associated with a frequency when the null condition of the second standing wave is proximate the detection point;
• detecting a null voltage level of the null condition proximate the detection point;
• and
• determining a ratio of a difference between the second voltage level and the baseline voltage level over the null voltage level, the ratio being indicative of the percentage content of the particles.

An apparatus for detecting a percentage of soot content in a quantity of diesel oil, the apparatus comprising:

• a variable frequency microwave source;
• a probe immersed within the oil;
• a microwave detector;
• and
• a processor coupled with the microwave source, the probe and the microwave detector, the processor configured to calculate a ratio of a difference between a baseline voltage level associated with a first standing wave and a second voltage level associated with a second standing wave over a null voltage level, the second voltage level and the null voltage level determined in response to a change in a relative permittivity of the diesel oil and wherein the ratio is indicative of the percentage of soot content.