Determining an estimate of soot load in a diesel particulate filter using a radio frequency sensor

An engine assembly for determining an estimate of soot load in a diesel particulate filter of the engine assembly, the engine assembly comprising an engine control module and a radio frequency soot sensor, the engine control module configured to:

• receive a first mean attenuation value derived from attenuation values for each of a first plurality of radio frequencies within a first band of radio frequencies detected by the radio frequency sensor;
• receive first standard deviation data for the mean attenuation value relating to the first plurality of radio frequencies within the first band of radio frequencies;
• determine whether the first standard deviation data exceeds a standard deviation threshold;
• (a) in the event that the first standard deviation data does not exceed the standard deviation threshold:
• use the first mean attenuation value to infer a value for soot load in the diesel particulate filter;
• (b) in the event that the first standard deviation data exceeds the standard deviation threshold:
• receive a second mean attenuation value derived from attenuation values for each of a second plurality of radio frequencies within a second band of radio frequencies;
• receive second standard deviation data relating to the mean attenuation value for a second plurality of radio frequencies within the second band of radio frequencies detected by the radio frequency sensor;
• and
• in the event that the second standard deviation data does not exceed the standard deviation threshold:
• use the second mean attenuation value to infer the value for soot load in the diesel particulate filter.