2 Channel Measurements

There are times when it is useful to take 2 simultaneous measurements and compare the phase (or position of the shaft) from one position relative to the other.  This is most commonly used with displacement probes on journal bearings and is a powerful diagnostic tool on this type of equipment, as well as provides you with the ability to create orbit plots.

 

Compare Phase in the NEST

To do this in the NEST software you will begin by:

  • Creating a template in the setup machine module.

Once there:

  • Select “Manage”
  • Then select “New machine Falcon”
  • Give your new machine, or your more accurate reading setup a name
  • Drag a motor down and enter in an HP and RPM (these values are arbitrary in the “Template” creation so simply put something in there – when you apply this point to a machine, it will use the values provided for that machine)

Once that is done:

  • Go to the measurements tab (which is where we will be setting up the readings)
  • On the “Measurements” tab you will need to change the “Setup input” to a displacement probe and enter a value for the sensitivity of your sensors
  • Next, hold the control button down and select two positions (horizontal and vertical)

Once you do this:

  • Select “Add” to create your readings (Relative displacement and Position are the two readings that you will want to create, they are listed under the “Parameter – Measured” menu option)

It is also useful to create both a time signal and a displacement spectrum which are located under signal.

There are many other readings you can create for this type of probe but I listed the primary ones above.

 

Creating Orbit Plots

You can also create orbit plots like you would by using displacement probes on both the Falcon and NEST software. Although the data will not be as accurate due to the limitations of double integrating the signal from acceleration to displacement, it can still be useful.

To take this kind of data, you will:

  • Create a machine and disable the Axial position
  • Set up custom measurements for this machine
  • And add a reading for a “Time Signal” similar to the image below on both horizontal and vertical points.

As long as you have the machine setup like this you will be able to view orbits on the Falcon itself.

Next you will have to:

  • Load this machine into the Falcon
  • Go to settings (we will need to change the measurement parameter to “Multi” and “Wired” for data collection – if we are using a wired triaxial accelerometer)

The setting will look like the image above.

After you get set up and acquire the data you will be able to:

  • Push the “Eyeball” icon to view the data on the time signal reading
  • There will be an option on the lower left corner of the screen to view and orbit plot

When you upload the data to the NEST you will also be able to:

  • View an orbit plot by selecting both the horizontal and vertical time waveform readings and opening them on one graph.

  • With the graph displayed on the screen go to “Processing/Orbit/Filtered(F0,H2,H3)” like the image below.

This will give you the orbit plot data filtered to running speed.

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