Bently Panel Measurements
The information provided is for help with Commtest Instruments products:
- vbSeries® instruments
QUESTION
How do I set up for taking displacement readings from a Bently panel, with assurance that my connection will not cause a voltage spike or a 'trip' on the installed system? How do I read directly from a Keyphasor® output on a Bently panel?
ANSWER
The Commtest vb3000 and vb7 instruments support the connection to a Bently panel to read the Keyphasor® signal and the displacement output signals from the installed proximity probes.
In order to make absolutely certain that the connection of the instrument will not cause a voltage spike to the installed system; it is recommended that the measurement be set up on the second channel as a displacement measurement with no power applied.
This is accomplished in Ascent in the parameter setup screen as shown below.
The sensor setup is as follows:
Note that drive current is not enabled. (on vb3000 instruments the Input Coupling is limited to AC only, so the sensor gap cannot be measured)
In the instrument, it is necessary to have CH2 enabled, as shown below:
A straight-thru male BNC to male BNC cable can then be used for acquiring the data.
For measurements where it is desired to take displacement readings on both channels for an orbit display, both channels would have to be set up for displacement and the appropriate scaling, say 200 mv per mil.
To be absolutely certain that no drive current is present from a previous reading with a default sensor on CH1, it is necessary to take an initial reading without connection to the panel and then a re-take or over-write that data with the proper connection.
For connectivity to the Keyphasor® output, the vb3000 requires a special cable CABK0108 which conditions the signal to match its TTL-style input. The vbX instruments have a different connector, so require cable KEY70258. The vbX instruments have the conditioning electronics built-in, and can be told which type of conditioning to use via the Tach Trigger setup option, as shown below.
FAQ ID: 19360 Last Reviewed: 29 November 2007