How do knock sensors work?
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On The Tree
Joined: May 2002
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From: san jose, ca
How do knock sensors work? I understand what they monitor. I am wondering how does it sense detonation? How does it tell the computer the motor is detonating?
Thanks in advance
<small>[ February 06, 2003, 11:36 AM: Message edited by: jrios ]</small>
Thanks in advance
<small>[ February 06, 2003, 11:36 AM: Message edited by: jrios ]</small>
Re: How do knock sensors work? http://kickme.to/KOBox
I have a good explanation on there for you. I'll be posting how to build these circuits soon. Gotta get some free time to do the write-up first <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
-Tony
I have a good explanation on there for you. I'll be posting how to build these circuits soon. Gotta get some free time to do the write-up first <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
-Tony
Re: How do knock sensors work? I read some of the datasheets for the
first knock sensor ICs and the basic
idea is this:
There is a transducer (microphone)
attached to one or two places on the engine
(usually the head). The transducer output
is filtered in frequency (for characteristic
engine resonances which pertain to spark
knock, eliminating other noise) and time
(only monitored within a certain window
about the spark point, to only "see"
preignition / detonation events and reject
other false inputs). The devices I looked
at had a bunch of "tuning" components off-
chip for making the right setup.
I don't recall anything about the interface
to the computer. I expect technology has
marched on, and the company I refer to
has closed the fab where they formerly
made these and has pretty much deemphasized
the automotive segment. You may still be able
to find datasheets and app notes though.
See
http://www.intersil.com/data/fn/fn3601.pdf
for an app note on these earlier knock sensor
ICs.
first knock sensor ICs and the basic
idea is this:
There is a transducer (microphone)
attached to one or two places on the engine
(usually the head). The transducer output
is filtered in frequency (for characteristic
engine resonances which pertain to spark
knock, eliminating other noise) and time
(only monitored within a certain window
about the spark point, to only "see"
preignition / detonation events and reject
other false inputs). The devices I looked
at had a bunch of "tuning" components off-
chip for making the right setup.
I don't recall anything about the interface
to the computer. I expect technology has
marched on, and the company I refer to
has closed the fab where they formerly
made these and has pretty much deemphasized
the automotive segment. You may still be able
to find datasheets and app notes though.
See
http://www.intersil.com/data/fn/fn3601.pdf
for an app note on these earlier knock sensor
ICs.
