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      08-24-2008, 06:33 PM   #55
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Drives: E92 M3
Join Date: Sep 2006
Location: San Diego, CA USA

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Originally Posted by ArtPE View Post

I think the units for noise is an RMS value (sqrt(noise V^2 ~ 'power')), hence the sqrt of (hz)
mg = g x 10^-3
the sensor looks like it was designed for vibration/shock analysis
say the g force range is 1g
if the f of oscillation is say 1hz, noise is 0.3 mg
if the f is 400hz the noise is 0.3/20 mg 0.015 mg

this is a good primer

non-linearity is 0.3%, which is kinda like the accuracy or repeatability...

how do I donate?
This sensor is actually quite special in that is has true DC response and very consistent sensitivity up to 500 Hz. I felt this was required for this testing. It was quite tough to locate. Many accels used in vibration and modal testing do not offer ANY DC output.

The error specs do not lend themselves to estimating errors during the DC or nearly DC periods and this is what I would like to have. They do explain why the sharply rising data section have less noise. Peaks have a great deal of high frequency content and if the noise decreases with increasing frequency that likely explains this observation.

I understand the linearity . FYI: I was an ME designing, building and testing precision pressure and force sensors for some time....

Donations can be made to me through paypal. I'll pm you. Thus far we have spent about $600 and I have been given 4 $100 donations. As well, as you probably read, Ken is donating time and materials to make a real mounting system.

Ken: One other point: If there is any way at all to make this a universal mount (i.e. for all or most cars) that would be great. I seriously doubt it is possible but if you examine a bunch of seat rails you may come up with a clever solution. Otherwise it is a new mount for each bloody vehicle.