turn on suggestions

Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.

Showing results for

- Navigation
- Simcenter
- Forums
- Blogs
- Knowledge Bases

- Siemens PLM Community
- Simcenter
- Testing Forum
- RMS Calculation

Options

- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Printer Friendly Page

Solved!
Go to solution

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Highlight
- Email to a Friend
- Report Inappropriate Content

12-20-2016 09:31 PM - edited 12-20-2016 09:39 PM

I exported some spectral data from LMS Test.Lab to Excel, and tried to reproduce the RMS/Overall calculation according to this formula I found in the online help of LMS Test.Lab:

I don’t get the same RMS value in Excel as I do in LMS Test.Lab!

Here is a screenshot from LMS Test.Lab:

The total RMS in LMS Test.Lab is 0.02554 g. In Excel, using the online help formula, it is 0.0443203 g. A screenshot of my Excel calculations is below.

Any ideas?

Solved! Go to Solution.

1 REPLY

Solution

Solution

Accepted by topic author TBake

12-20-2016
09:39 PM

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Highlight
- Email to a Friend
- Report Inappropriate Content

12-20-2016 09:37 PM - edited 12-20-2016 09:41 PM

Hi,

Noticed that you had *peak* data values with a Hanning window. The data values are amplitude corrected (factor of 2) for a Hanning window.

The *RMS total* is based on individual *rms* values which are energy corrected (factor of 1.633). Other windows (Flattop, etc) have different amplitude and energy correction values.

To get the correct total RMS value you must:

- Multiple the peak values by 0.707 to convert to rms
- Divide by 2 to remove amplitude correction
- Multiply by 1.633 to energy correct
- Square all the values
- Divide the last and first squared value by 2
- Sum all the squared values and take the square root

Here is a screenshot from Excel, with one of the key formulas showing:

The rms and energy correction is also mentioned in the online help, although an example is not given:

Doing the extra rms and energy correction with the same 10 values you showed in your example gives the correct RMS total of 0.02554 g

Follow Siemens PLM Software

© 2017 Siemens Product Lifecycle Management Software Inc