Sorry - noisy in the signal conditioning sense, not in the 'clackity clack'
sense. Accelerometers generally have a signal 'noise' associated with them, as
do
all measurement devices. My understanding (I could easily be wrong on this, as
most of my measurement experience is with thermal stuff, not mechanical, though
Ive used accelerometers a bit) is that low priced ones give enough noise off
(i.e.
just random signals) that they would be difficult to use and not so good for a
safety critical system like ABS.
Course, I could be way off base on the 'noise' bit. Thats what I was told by a
guy that has done some research in the field when I asked this exact question
about a year ago.
A. Arabian
REwald9535@aol.com wrote:
> In a message dated 01/21/2000 10:57:47 AM Pacific Standard Time,
> arabian@allegronet.com writes:
>
> > A number of cars use accelerometers, but NOT for axial deceleration
> > measurement
> > generally. They are for lateral acceleration - i.e. cornering. The ABS
> > operates slightly differently when cornering than when going straight (more
> > braking on the inside wheels I think, but I could be way off base on that.
> > Don't remember the specifics). Anyway, my guess based on my limited
> > measurements experience is that accelerometers (or at least reasonably
> > priced
> > ones) are just too noisy to be used very well for axial deceleration.
> >
> As far as I know no ABS system uses accelerometers. the wheel speed sensor
> uses a toothed wheel and some type of pickup (magnetic is the most common) A
> magentic sensor generates a sine wave and the signal goes to an analog to
> digital converter (typicaly a Schmit trigger) this A to D converter may be in
> the control unit on in the sensor. The control unit is just looking at the
> frequency of each wheel and calculates G force from changes in frequency of
> each wheel.
> Accelerometers are used in yaw control systems, my company car has one. I do
> have one question, your comment about noisy? The sensor in my car is solid
> state and as such is stone silent. How do the ones in your experience work?
> Rick Ewald
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