[Diy_efi] Question on Knock Sensors

[Carter Shore]

Using the same sensor as both the driver and receiver
will give an unrealistic result.
The knock sensors are resonant piezo elements, which
means that when used as drivers, the output sound
level will also peak at the resonant frequency, even
though the excitation voltage is maintained at 1V pp.
So of course all of the sensors will appear to have
similar frequency response.
It would be more accurate to use a broadband element
like a hi-fi speaker as the excitation element. The
sensors under test could be rigidly attached to the
speaker frame, or perhaps even just suspended directly
in front of the speaker, driven through an amp.

Carter

> .... I have profiled the
> sensors by getting a 1/4
> NPT pipe coupling and screwing one sensor in one end
> and another sensor in
> the other end. I set up with 2  DR562      sensors.
> I applied a sine wave
> from a HP 3324A to one sensor and looked at the
> output of the other sensor
> with a Nicolet 440 scope. with 1 VPP amplitude I
> sweep the frequencies from
> 1Khz to 50 Khz The highest amplitude was always at 6
> Khz. Of the 14 sensors I tested they all responded >
the same. I concluded that the sensors
> are not all that different and could be
> interchanged.I then tested 9
> external det modules from AASS,HKD,HKR,BLN,ANBZ ect.
>  The output is 10 volt
> until between 4 Khz and 12 Khz the output would go
> low . Again 6 Khz was the sweet spot.     



		
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