Tri-ax accelerometer cross couple
Tri-ax accelerometer cross couple
(OP)
we recently ran a sine sweep and several random sweeps on a new vibration fixture to verify that we can pass through the various excitations frequencies of the fixture and still meet the customer req for deviation from expected input data.
We used a tri-ax accelerometer as our control, and the axis being tested passed all testing with flying colors. We did however notice at high freq, around 1khz (where we believe our first naturual freq of this fixture to be) the other two axis went from ~0Grms to levels similar to the control axis, even tho the control axis was spot on what it should be. The accelerometer was secured with wax near the product interface.
our customer is fine with this, as they have no requirements for cross coupling.
Should I be concerned? anything else to look at? i've never used a tri-ax like this so this was unexpected and want to explore further?
We used a tri-ax accelerometer as our control, and the axis being tested passed all testing with flying colors. We did however notice at high freq, around 1khz (where we believe our first naturual freq of this fixture to be) the other two axis went from ~0Grms to levels similar to the control axis, even tho the control axis was spot on what it should be. The accelerometer was secured with wax near the product interface.
our customer is fine with this, as they have no requirements for cross coupling.
Should I be concerned? anything else to look at? i've never used a tri-ax like this so this was unexpected and want to explore further?





RE: Tri-ax accelerometer cross couple
RE: Tri-ax accelerometer cross couple
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Tri-ax accelerometer cross couple
However, since the axis in question is the control, the closed loop nature of the table handles this quite well and eliminate the increased amplitude/accelerations of the resonance.. so i was suprised to see some of it in the other axis. it sounds like this is just the way it is... and we should move on?
RE: Tri-ax accelerometer cross couple
Anyway, yes it probably doesn't matter.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Tri-ax accelerometer cross couple
1) Are the resonances causing damage to the fixturing?
2) Do the resonances cause unrealistic damage to the specimen?
If the customer isn't bothered (he/she may not know better) then question one is your only concern.
RE: Tri-ax accelerometer cross couple
The UUT is relatively light and the table/fixture is rather "serious".
I do not have a problem with it, and we do not see failures. We are moving right along, but I was able to talk upper management into giving me time(money) to at least look at it- I would like to learn something if there is anything to learn. Sounds like this is expected/normal. My Q in one of the axis is less than minimal, the other is around 4.5 which is still low.
RE: Tri-ax accelerometer cross couple
RE: Tri-ax accelerometer cross couple
I recall I stumbled across a tech article recently about the limitations of triaxial accelerometers for machine monitoring. I could not find it when I just re-Googled. My recollection is 2 axes were often best limited to a few orders of rotation (few hundred Hz)