Bump Tests

The information provided is for help with Commtest Instruments products:

Ascent®/MAS VB, vb instrument

QUESTION

How do I perform a bump test using my vb instrument? I want to use this as a quick way to determine the resonance frequencies in a machine structure.

ANSWER

If you are using vb firmware 3.00 or later choose Bump Test from the Measurement Menu. The parameter settings listed below will be automatically applied for you. Follow the instructions from 'Taking the Measurements', further down this page.

If you are using a firmware version prior to 3.00 follow the procedure below.

From the instrument Main Menu press [1] to enter Measure Mode.
From the Set Parameters Menu reset the instrument to factory default settings by pressing SHIFT+RESET.

Set up a measurement with the following parameters:


Fmax	5X Running Speed (suggested)
Averaging	Peak Hold

Optional changes depending upon your preferences


Quantity	Displacement
Channel	CH1 & CH2
Units	Your preferred units e.g CPM or in/s (set this parameter in Display Options)

Note: In free run mode with peak hold averaging the vb instrument will continue sampling and keeping the peak values for each spectral line until the parameters are changed or you go to the Main Menu.

Taking the Measurements

Press START/STOP to begin sampling.
Hit (i.e. 'Bump') the machine with the hammer.
Repeat several times.

Tips/tricks

Press [3] then ENTER to clear the spectrum
Press [8] to toggle the channel displayed if both CH1 and CH2 are being measured.
Use the up and down arrow cursors to check the frequency of any resonance peaks found.

Storing the Measurements

Press START/STOP to stop the FFT from being updated.
Press MENU to display options for storing the currently displayed channel or both channels.
Select the machine, point and direction(s) when prompted, to indicate where the data should be stored.

Note: If using both channels you must store the measurements from each channel at a different direction/axis as Ascent/MAS VB identifies recordings by their date/timestamp and direction. If the date/timestamp of two recordings is identical at the same direction in the instrument, one recording is discarded).

FAQ ID: 11651 Last Reviewed: 01/11/2005