Design Con 2015
Breaking News
Comments
Newest First | Oldest First | Threaded View
Steve.Picotest
User Rank
Blogger
Re: When to use averaging
Steve.Picotest   9/26/2013 1:59:49 PM
NO RATINGS
1 saves
This is a great question, though not a particularly simple one.  Some applications that would seem obvious to use averaging can be problematic, for example looking at the switch node in a power supply or a step load would seem like a suitable time to use averaging, but in many cases this isn't so. Another example is the step load of a POL, which often has large signal effects, so each cycle can be different than the one before or after it.  The switch node often has jitter in switching frequency and/or pulse width as well as amplitude modulation.  These artifacts would all be averaged distorting the the result or failing to let you see them. 

 

One time that you would want to use averaging  is to isolate a signal that is mixed with other signals.  Say you want to isolate the switching ripple from load induced noise (such as a step load).  If the scope is triggered on the switching frequency averaging will keep the switching ripple result and average out all other signals so long as the other signals are not synchronized to the switching frequency.

One way to tell if averaging is resaonable is to switch on persistance mode.  If the resulting waveform envelope is very small averaging is probably ok, but if the envelope is significant don't use averaging. 

If there is any doubt, skip the averaging.

The impact of averaging on the measurement can be substantial and a picture is worth a thousand words, so maybe I will do a blog on the subject. to appear after part 4 of this one.

 

Thanks for the great question.

 

Steve

 

Steve.Picotest
User Rank
Blogger
Re: When to use averaging
Steve.Picotest   9/26/2013 1:59:46 PM
NO RATINGS
1 saves
This is a great question, though not a particularly simple one.  Some applications that would seem obvious to use averaging can be problematic, for example looking at the switch node in a power supply or a step load would seem like a suitable time to use averaging, but in many cases this isn't so. Another example is the step load of a POL, which often has large signal effects, so each cycle can be different than the one before or after it.  The switch node often has jitter in switching frequency and/or pulse width as well as amplitude modulation.  These artifacts would all be averaged distorting the the result or failing to let you see them. 

 

One time that you would want to use averaging  is to isolate a signal that is mixed with other signals.  Say you want to isolate the switching ripple from load induced noise (such as a step load).  If the scope is triggered on the switching frequency averaging will keep the switching ripple result and average out all other signals so long as the other signals are not synchronized to the switching frequency.

One way to tell if averaging is resaonable is to switch on persistance mode.  If the resulting waveform envelope is very small averaging is probably ok, but if the envelope is significant don't use averaging. 

If there is any doubt, skip the averaging.

The impact of averaging on the measurement can be substantial and a picture is worth a thousand words, so maybe I will do a blog on the subject. to appear after part 4 of this one.

 

Thanks for the great question.

 

Steve

 

MeasurementBlues
User Rank
Blogger
When to use averaging
MeasurementBlues   9/26/2013 8:01:00 AM
NO RATINGS
>The averaging function is useful in cases where the measurement is very consistent and the noise you wish to eliminate is not time correlated with the measurement.

Steve, can you give an example of when to use avaraging?



Most Recent Comments
SpaceBug
 
_hm
 
_hm
 
David Ashton
 
R_Colin_Johnson
 
rick merritt
 
pguptaca
 
MeasurementBlues
 
MeasurementBlues
Most Recent Messages
11/26/2014
7:38:46 PM
Flash Poll
Top Comments of the Week
Like Us on Facebook
EE Times on Twitter
EE Times Twitter Feed

Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)
EE Life
Frankenstein's Fix, Teardowns, Sideshows, Design Contests, Reader Content & More
Max Maxfield

Book Review: Deadly Odds by Allen Wyler
Max Maxfield
8 comments
Generally speaking, when it comes to settling down with a good book, I tend to gravitate towards science fiction and science fantasy. Having said this, I do spend a lot of time reading ...

Martin Rowe

No 2014 Punkin Chunkin, What Will You Do?
Martin Rowe
Post a comment
American Thanksgiving is next week, and while some people watch (American) football all day, the real competition on TV has become Punkin Chunkin. But there will be no Punkin Chunkin on TV ...

Rich Quinnell

Making the Grade in Industrial Design
Rich Quinnell
13 comments
As every developer knows, there are the paper specifications for a product design, and then there are the real requirements. The paper specs are dry, bland, and rigidly numeric, making ...

Martin Rowe

Book Review: Controlling Radiated Emissions by Design
Martin Rowe
1 Comment
Controlling Radiated Emissions by Design, Third Edition, by Michel Mardiguian. Contributions by Donald L. Sweeney and Roger Swanberg. List price: $89.99 (e-book), $119 (hardcover).