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Accelerometer selection

Accelerometer selection

Accelerometer selection

(OP)
One of our products recently underwent a random vibration test at an external test house. The test was completed as per our test procedure (3 point control on the test fixture using a maximum control strategy with the location of the control and monitor lines as specified in the procedure). Following review of the results, everything is fine and the unit has undergone a post vibration RF functional check with no issues.

However, the test report details of the ISP control accelerometers used and they have different sensitivity values (2 @ 10mv/g & 1 @ 100mv/g). My limited understanding is that sensitivity of the control acc should be based on the input spectrum in order to ensure that the test doesn’t exceed exceed the limits of the acc (and conversely, ensure the output is sufficiently large). However, how do you verify the ‘correct’ acc has been used?

Are there any issues with mixing acc of different sensitivities? Presumably for the same test criteria, the higher sensitivity acc has a higher potential to be overloaded than the lower sensitivity acc ones?

Thanks for help as the above is outside my usual field
G

RE: Accelerometer selection

Not an issue, generally. The front end to the analyser has a table of some form where the sensitivity of the accelerometer is entered.

Of course if they haven't set that correctly then there are problems.

They should be checking for clipping etc, most systems have red lights and so on to discourage the user from running into clipping. The more likely issue is that the less sensitive accelerometers would generate more noise at a given signal level.

Cheers

Greg Locock


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RE: Accelerometer selection

(OP)
Thanks for the info, Greg.

The test report has the selftest results and the sensitivity values have been set as per the acc calibration info and the gain stteings are fine.

My query was that I noticed different acc sensitivity values and wanted to knwo the rational behind it and whether it has any influence on the test results (for reference, the input spectrum goes from 20Hz-2kHz with an input RMS of 21 Grms with most of the energy between 60 & 250Hz as the PSD level is 1.6g2/Hz).

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