Eddy Probe Side View

Normally "X" and "Y" vibration probes are measuring movement in different planes which would account for the difference in readings.

If both sensors are actually in the same plane it could be that the interconnection cables from the probes are not of the same length or are not of the same cable type (different size conductors or different twist per mm) or there is a loose connection somewhere in the circuit.

Also; If the scaling and/or range are not set to the same value in the configuration file(s) there will be a difference in readings.

In some cases there is an impedance nulling parameter that must be activated when different lengths of cable are used.

If you have not done so, it would be a good idea to contact Rosemount Technical Support.

Hi

As theory says, if proxi probe reads high vibration , Dc gap volatge also must be change, Initially, it was -10V so, it supposed to be change while showing high vibration, am i right? what if GAP voltage is not change means?

As per sensor sensitivity, 200mv/mil,if 10 volt means 50 mills. from probe tip to surface.

if probe reads high vibration means, 50 mills need to change? right?

Hi we using 3300XL proximeter system and we did set -10V as Gap voltage, hence we observe X,Y vibration discrepancy.. Where one is showing high vibration 55 mic and other one showing very low vib 15 mic.as per theory, when gap voltage decrease then vibration gets up. I found for this system has a linear range Up to -13 v, if we change the concern probe ( the one having high vibration) gap voltage to -13 V, will vibration can come down? We again did open the turbine, nothing found, clearance,lube oil properties, journal bearing, pipe stress, soft foot all are in range. Though we changed probe, proximeter, cable, card, etc etc.. No result. We decided to play with gap settings, shall we go forward?

Hi,

Try using the X plane probe that is giving you 55 mic reading in the Y Plane and Y plane probe in X plane by interchanging.

If both 55 mic and 10 mic readings remain same, then you can say that since the Original Y probe which you suspected of wrong reading is showing the same value (55 mic) which the Original X probe was showing, hence the probe is alright.

If the readings interchange with probe (*highly unlikely) then try to look in to sensor for issues.

Hope this helps...

PVL