Coast-down/Run up
Note: This feature is not available on the vb5 or vb6 instrument models.
Coast-down and run-up measuring involves taking a series of recordings with a short delay between them. This technique can be used to study the resonance behavior of a machine as its speed gradually increases during power-up, or decreases during coast-down.
- From the Main Menu press
Measure and use the left-hand arrow keys to highlight Coast-down/Run-up then press 
. - Use the left-hand arrow keys to select a parameter set or press
to create a new one and set the parameters as required. - Press and select the machine location to save measurements to, then press again to begin measuring. After the first spectrum has been recorded switch off the
machine, or begin ramping its speed up or down. - Once the machine has stopped rotating, or its speed has been fully adjusted, press
to stop measuring and return to the Coast-down/Run-up Menu.
The measurement location will contain a large number of measurements. You can transfer these to the Ascent software and display them as a waterfall chart, and as a bode plot if you used the tachometer as well.
Recommendations
We recommend using a tachometer to obtain the RPM reading for each measurement as this aids interpretation.
You can set the Recording Interval as either a time interval between recordings, or as a change in machine RPM. We suggest using the latter, with the RPM Difference set to machine speed / 20. This will result in approximately 20 recordings being taken during a complete coast-down or run-up.
A large number of recordings are taken during a coast-down or run-up. If you intend to repeat the process several times on a machine we recommend you save each set of recordings to a separate location so that they can be easily distinguished.
Last Reviewed: 11/Jun/2009 Source: vbSeries Reference Guide Revision 24 Mar 2009 - pages 73 & 74