## MaintenanceForums

Hi all,

I have question that is driving me crazy.

If I have a rotating disc (think about a fan or whatever), and instead of measuring with the accelerometer in the non-rotating part, bearings or so, If I attach an accelerometer (triaxial and wireless of course) in the perimeter of the disc, do you think i would measure a 1x, 2x, 3x components of the rotation?

don't go for application issues it is just a didactical question. If the accelerometer is attached to the rotary part I am thinking that the inertial mass of the piezo will be moving inside the accelerometer casing and at the same time the disc is rotating... which acceleration components would I measure? tangential, normal, Coriolis.. My concern is whether i will be able to read a 1x synchronous component or not

thanks and happy tuesday!

Tags: accelerometer, 1x

thanks!

so, I would measure torsional vibrations by placing the accelerometer in an eccentric position...

My understanding is that two tangential accelerometers, 180-degrees apart, are needed to cancel (by subtraction) the lateral motion from pure torsional motion. I would be more convinced with the Erbessed-Instrument "experiment" if another direct measure of torsional vibration was used for comparison. Perhaps for that experiment the torsional motion was dominant compared to lateral motion. I use the optical encoder method (located for high torsional displacement/velocity) and the Binsfeld strain-telemetry (located for high torsional strain).

A triaxial accelerometer would presumably be oriented for axial, radial and tangential (torsional) vibrations. A rotating coordinate system is expected to be different from the stationary X-Y-Z coordinates on the bearing housing. I know it is possible to balance a large slow speed fan using torsional vibrations! If you want to add any sensor mass that is eccentric to shaft axis, then you should balance it with an equal and opposite mass to maintain the integrity of the vibration measurement.

Walt

interesting Walt, for sure another mass 180 degrees apart is necessary to cancel the unbalance of the sensor

Then you answered one of my concerns. Setting up the sensor in the rotary part perimeter, tangential, axial and radial for the triaxial sensor, it is possible to still read an amplitude and phase value and perform a balancing. I will take in mind and try to do if I have the opportunity

i thought, beeing the unbalance 1x synchronous component and with a constant rotating speed (no tangential acceleration)the sensor wouldn't read anything in 1x harmonic.

Regards

Last edited by Registered Member