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Bently Nevada probe gap adjustment
How to configure the gap for the BN probes in the MKV and MKVI panels

Would like to know from someone in the on how the configuration for the Bently Nevada probes done in MKV and MKVI panels.

My question is about configuring the gap voltage settings for radial and axial probes of Bently Nevada probes connected directly to MKV and MKVI panels without the Bentley Nevada monitoring system. On which pages can we see the settings for the gap voltage for radial and axial probes?.

What is the advantage in connecting the Bentley probes directly to the MKV and MKVI panels without using the Bentley Nevada monitoring panels.

A reply from anyone in the would be highly appreciated.


Best connection point for the Bently Nevada proximity probes depends on whether your turbine is gas or steam.

For a GE gas turbine, the Bently Nevada probes are used for monitoring and alarm, not trip protection (seismic probes are used for protection), so best practice is to connect the probes (proximators) to the Bently Nevada monitors. The analog output from the monitors is connected to the Mark V or Mark VI control for indication on the turbine control displays and logging in the Historian (if applicable).

For a GE steam turbine, the Bently Nevada probes are used for protection and should be connected directly to the Mark VI turbine control; I believe the same applies to Mark V, but it has been a while since I was involved in a Mark V project. The turbine control then repeats the signal to the Bently Nevada monitor.

You set the gap voltage as close as possible to the center of the linear span, and zero out your reference from there. There are various offsets you can use once the gap voltage is set to determine trip setpoints and alarm setpoints or to massage the signal once the raw voltage is input to the TVIB card.

GEH-6421 Volume II on the VVIB cards describes how to set up the probes directly to the MKVI. The only advantage I see with paralleling to the BN cabinet would be to send the information to system 1 as we do here at Hope Creek. Any questions please feel free to contact me.

Anthony Mesiano
Hope Creek Generating Station
Electrical/I&C System Engineer
Anthony.Mesiano [at]

By Vib Gap Voltage on 8 January, 2010 - 1:56 am

If you have used bently nevada vib system that could show gap voltage from bently nevada sysytem. But You have to know connect monitor system. Hepas of time i adjusted 9 volts Dc .

2 out of 2 members thought this post was helpful...

True statement on the center of the linear range, typically (-1) to (-18) VDC. To make it simple, gap vibration probes for either (-10, or -10.5, or -11) VDC. As for the Thrust, assume the center zero is -10 VDC. With the rotor barred active say 12 mils, total float 24 mils, set the probe for -12.4 VDC.

12 x .2 = 2.4 VDC, plus the -10 VDC for the center. Ask the turbine crew to bar the rotor inactive then active 3 times to verify the readings and repeatability.

Most end users get into trouble with position measurements. I can assist.

Ken Hoellger

1 out of 1 members thought this post was helpful...

Excellent reply Ken, well done, I fully agree with Ken's reply.

By vineet buxy on 1 April, 2015 - 12:07 pm

can you pls explain from where we get this .2 value in 12*.2 thing..

calculated from temperature change.

Example calculation: 12 inches (300 mm) of 4140 steel with a temperature change of 100F (38C) will grow 0.008 inches (0.2 mm). Therefore, the measurement will show 8 mils. of apparent thrust motion that is due only to thermal growth.

Mine question is that -10V gap voltage setting is for new type of vibration probes and corresponding proximitor 3300series 5mm/8mm.
What about the old type of vibration probes and their corresponding proximitor 7200 series 5mm/8mm. What is the recommended gap voltage setting for old type?

By Bobby Keen on 30 May, 2019 - 5:12 pm

How do you get the probe set correctly to neutralize any shaft run out when using these to measure vibration?

We are showing over (3) mills but it is not an accurate value.

>Mine question is that -10V gap voltage setting is for new
>type of vibration probes and corresponding proximitor
>3300series 5mm/8mm.