Octave Band Analysis with Ascent

The information provided is for help with Commtest Instruments products:

• Ascent®/MAS VB versions 7.xx and later

QUESTION

Can Ascent/MAS VB be used to perform 1/3 octave analysis?

ANSWER

You can use band alarms to achieve 1/3 octave style analysis by creating power based band alarms at 1/3 octave intervals.

Setup

Download the appropriate file below which contains pre-setup 1/3 octave band alarms. You can use these band alarms to perform 1/3 octave analysis on your own data.

• If you are running Ascent 7.41 or lower click here to download this file to your PC.
• If you are running Ascent 8.00 or higher click here to download this file to your PC.

Using the Band Alarms

Note: Although not strictly necessary we advise you to remove existing alarms from your selected location before applying the imported alarms.

• If you are running Ascent 7.41 or lower open a location in Ascent/MAS VB and double-click the downloaded file to import the band alarms.
• If you are running Ascent 8.00 or higher open a schedule entry in Ascent/MAS VB and double-click the downloaded file to import the band alarms.

These band alarms are set for velocity units and all thresholds are 1 mm/s rms. However, you will see what is effectively a third octave summary at the top of the spectrum plot.

Third octave analysis example one

(Click either of the images below to enlarge them.)

The yellow highlighting indicates that the level in that band exceeded 1 mm/s rms. This threshold is arbitrary.

Example two

Changing the Band Alarms

Once you have plotted some data you can rescale and resize the band alarm display at the top of the chart by moving the mouse over a power band alarm and pressing and holding down the right mouse button.

• Drag up and down to change the size of the band alarm display area.
• Drag left and right to change the scale/range.
• Change the thresholds (alert, warning, danger) of a band by double-clicking a band to open the Alarm Band Editor. Reset the thresholds or add new ones by selecting a threshold and typing in new values.
• Change the font color of the band alarm text by selecting Options>Edit/Change Scheme. Scroll down the list to the Band Alarms folder and double-click Alarm Band Text within this folder to open the Font window. From here you can change the font, color, and size.

Note: More detailed instructions for editing alarms can be found in your Software Reference Guide.

Re-using the Band Alarms at Other Locations

Once the band alarms have been imported to one location you can store these alarms in the Ascent/MAS VB library for quick access. The library is used to store commonly used components so that they can be quickly retrieved and reused.

• To store the band alarms, right-click the alarm icon that was created in the navigator list after import and select Library>Add Selection to Library.

Full instructions on storing and retrieving items in the library can be found in your Software Reference Guide.

FAQ ID: 11791 Last Reviewed: 01/11/2005