As I recall I could never get anything other than a Hz signal from them.
Actually everyone is correct in their own way.
One test is done to test the Bias Line Voltage which is in DC volts measurement.
because the bike is in fact a DC electrical system.
Bias line voltage is a circuit integrity check for computer.
and then the signal produced when activated is an AC voltage, measured in HZ.
The Ac voltage runs along the Bias line voltage.
By tapping on engine block or near sensor it should send a signal and should be able to read on Ac volts scale as well, as HZ scale.
And Kudos to John, John you would be surprised how many times for example
Mechanics I have worked with will condemn an Ignition coil on a car with multiple coils.
Without fully testing it. They could have moved the suspected coil to another cylinder.
And see if problem follows the swapped Cyl. You John did this on your bike by swapping around Knock Senor to prove it was good or bad.
For that I give you a gold star....bravo