Bump Tests vbClassic
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:
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Fmax |
5X Running Speed (suggested) |
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Averaging |
Peak Hold |
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Optional changes depending upon your preferences
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Quantity |
Displacement |
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Channel |
CH1 & CH2 |
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Units |
Your preferred units e.g CPM or in/s (set this parameter in Display Options) |
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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.
MORE INFORMATION
For more detailed information you can purchase the technical paper 'Natural Frequency Testing' from Technical Associates of Charlotte, P.C.
FAQ ID: 11651 Last Reviewed: 1 November 2005