Paul,
The following is extracted from the Probst manual, page 90-91. The book
goes into far greater detail and includes sensor testing info.
Think of the KS as a tuning fork. When excited by certain vibrations, it
resonates and produces an AC signal of 6-9Khz, depending on the specific
design (depends on the resonant frequency of the particular engine design).
The amplitude of the KS signal will be up to 4-5 Vac.
If you have an o'scope available, this should be really easy to see just by
tapping on the manifolds with a hammer with the engine running.
Steve