Thanks, Dave.
Great info.
Russ, #1226B
-----Original Message-----
From: Dave Dahlgren [mailto:ddahlgren@snet.net]
Sent: Tuesday, February 25, 2003 12:15 PM
To: Russel Mack
Cc: James Tone; wmtsmith@landracing.com; Doug Odom; Land Speed List
Subject: Re: data recorder
I think what it really comes down to is what do you want to measure and what
budget do you have.. Most things can be done in various ways with different
degrees of accuracy and reliability. The distance to the right of the
decimal
point becomes ground zero for spending money. In most cases if the
information
you are looking for can be expressed as an integer or X.X then you are fine
with
the low cost(edelbrock and others in that price range). If the correct
reading
has to be X.XXX and at 1000Hz then multiply your budget by 10.
Looking at what we measure in LSR racing anything in X.X range will do just
fine
as there are very few high speed transients to look for. The accel rate of
the
car is low as is the engine speed rate of change. The chassis is another
matter
but there is very limited movement and no turns.. One of the real features
of
the high end stuff is the ability to measure different channels at different
speeds though. The edelbrock unit does not have this so you end up with a
water
temp that is read way too fast and wasting memory.. Do be careful though and
not
buy a system just for this feature as it does ot make it a high end system.
the
real question to ask is the number of bits the A/D converter uses and the
sample
rate of all channels. the other thing to ask is how many A/D converters are
in
it as this effects the sample rate and settling time. A good example is the
egt
and the water temp. If they are both using the same type of sensor with the
same
voltage range and one is 1300 and the 175 you need longer to have the system
settle to an accurate reading, you can at times even get some aliasing
between
the channels due to this. In the edelbrock unit I always use 2 boxes(K wire
amps) for egt's and another for water temp and oil temp for this reason.
There
are a lot of other gottcha's as well but they are pretty easy to work out in
the
end.
The place I would speed the money in a LSR data acq system is the quality of
the
sensors in relation to corrosion resistance though.
Dave
Russel Mack wrote:
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