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help a rookie out part 2

Question asked by robcornish on Apr 17, 2014
Latest reply on Apr 29, 2014 by NevadaMark
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related question: http://ez.analog.com/message/138883

 

So I am doing shock testing using an ADXL001-500 and a DAQ (links to data sheets below) and I get the feeling that I something is not going quite right along the way. The idea is for each drop of an object, to get the maximum amount of G force it will experience. I am operating at a 5V input, and the accelerometer zero-offset voltage is about 2.32V +/-  0.04V (measurements while sitting stationary on a table). On any given drop I take the minimum and maximum voltage experienced, take the absolute value of (min/mix minus the offset of 2.32), and then convert the larger number from a voltage into Gs by dividing by the accelerometer sensitivity (in mV/g). Once finished I have a max Gs number that doesn't seem to be quite right.

 

To give an example, say on one drop I see a max V of 4.4719V and a minimum of 1.6184V.

     For this I would use the max V, with a difference of 2.1479V

     The sensitivity on the data sheet for the adxl001-500 at 5V says 3.3mV/g = 0.0033V/g

     To convert the max reading into Gs I would do 2.1479/.0033 = 650.8788

This makes me scratch my head since this is only supposed to be a +/-500g accelerometer

 

Any ideas as to why this might be happening or what I should do to fix this? I'm still relatively new to all this. Thanks for any and all help.

Rob

 

links to datasheets:

http://www.analog.com/static/imported-files/data_sheets/ADXL001.pdf

http://www.mccdaq.com/PDFs/specs/USB-1608G-Series-data.pdf

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