Coil on plug signal detection

A diagnostic apparatus for use in analyzing ignition signals generated by a coil on plug, the apparatus comprising:

• a signal detector comprising a first conductive planar layer and a second conductive planar layer separated by and affixed to an insulating substrate, said signal detector being disposed within a housing configured for placement outside of and in close proximity to a coil of the coil on plug housing with said second conductive planar layer interposed between said coil on plug housing and said first conductive planar layer;
• a signal wire coupled to the first conductive planar layer and coupled to a signal input of a signal analyzer;
• and
• a ground wire coupled to the second conductive planar layer and coupled to a ground input of the signal analyzer and the ground of the coil on plug,
• wherein said second conductive planar layer and said ground wire are configured to attenuate a portion of electromagnetic radiation incident to said first conductive planar layer from said coil.

A method of measuring electric ignition signals of a coil on plug of an internal combustion engine, the method comprising the steps of:

• holding a signal detector, comprising a first conductive planar layer and a second conductive planar layer which are separated by and affixed to an insulating substrate, outside of and in close proximity to a coil on plug housing with said second conductive planar layer interposed between said coil on plug housing and said first conductive planar layer;
• coupling a signal wire from the first layer to a signal input of an electronic signal analyzer;
• coupling a ground wire from the second layer to a ground input of the signal analyzer and the ground of the coil on plug;
• attenuating a portion of electromagnetic radiation incident to said first conductive planar layer from a coil of said coil on plug using said second conductive planar layer interposed between said coil on plug housing and said first conductive planar layer;
• and
• obtaining a measurement of the electric ignition signals using the signal analyzer based on detection of the electric ignition signals by the signal detector.