combustion pressure sensor

[Larry Heath]

I think that they are using this device to detect the high frequency
pressure/shock waves or characteristic "ring" that are generated by
detonation and transmitted throughout the engine. Question is if it
"directly measures" or only indirectly corresponds to actual in cylinder
pressure or it generates a voltage signal variation based upon a change in
the local stresses and strains associated with the base stress and strain
induced in the sensor by the torque applied to the sparkplug. Therefore
every time you change the sparkplug(s) you would achieve a different base
voltage/calibration. After all this is or appears to be a simple pizo strain
gauge. You may be looking for or at signals that are only minute high
frequency variations on an overall base voltage that is generate in the
sensor by the torque/pressure applied buy the sparkplug and does not
"directly" read cylinder pressure. True pressure transducers use a much
thinner "window" that is directly exposed to the pressure and to which the
strain gauge is mounted or attached.  Now it appears to me that the
variations from one cylinder to another and from engine to engine and from
model to model would generate and insurmountable calibration curve problem
if one was trying to use the sparkplug/cylinder head as this window.

Now of course if each cylinder was equipped with one of these sensors then
one could detect which cylinder and at what point in engine relative time
detonation set in and a relative severity for the detonation.

Until someone gets more info on this device and its required associated
electronics and or calibration curve this is all speculation.

Later Larry

----- Original Message -----
From: "Rausch, Bernd" <br at rnt.de>
To: <diy_efi at diy-efi.org>
Sent: Friday, May 04, 2001 8:44 AM
Subject: AW: combustion pressure sensor


> They call it "a unique approach in measuring severity of knock in gas
> spark engines", and "it yields an output voltage that corresponds to
> cylinder combustion pressure".
>
> regards,
> Bernd
>
> -----Ursprüngliche Nachricht-----
> Von: Larry Heath [mailto:lgheath at earthlink.net]
> Gesendet: Freitag, 4. Mai 2001 14:16
> An: diy_efi at diy-efi.org
> Betreff: Re: combustion pressure sensor
>
>
> From your subject line I think that your barking up the wrong tree here.
> This is a "KNOCK" sensor or at least that is what their calling the
> thing.
>
> Not that this might not be a bad tool, its just not a combustion
> pressure
> sensor.
>
> Later Larry
>
> ----- Original Message -----
> From: "Rausch, Bernd" <br at rnt.de>
> To: <diy_efi at diy-efi.org>
> Sent: Friday, May 04, 2001 7:34 AM
> Subject: combustion pressure sensor
>
>
> > looks interesting, does anyone know this senasor ?
> > http://www.pcb.com/products/custom/cus140m05.html
> >
> > Bernd
> >
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