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Waveform averaging - the PicoScope way

Forum for discussing PicoScope version 6 (non-automotive version)

Waveform averaging - the PicoScope way

Postby Pico Stuart » Thu Aug 28, 2014 4:07 pm

PicoScope 6 has a wealth of features available at your fingertips including some really excellent advanced maths channels.

Advanced Maths Channels

This feature can be found by going into Tools->Maths Channels, then clicking “Create”, and the “Maths Channel Wizard” will appear.



• Clicking Next will allow the user to enter basic equations.

Math Channle wizzard.jpg
Maths Channel Wizard


• Clicking the Advanced button will reveal further buttons.

advanced button step 3.jpg
Advanced Math Channel Wizard


• The min, max, x - bar *(average) and peak (also known as envelope) works on multiple waveforms/buffers. Here, x - bar is chosen on channel A.

*
average.png
* Average Symbol
average.png (2.77 KiB) Viewed 4121 times


• After clicking Next, the channel name and colour can be defined.

maths channel wizzard colour selection..jpg
Channel name and colour selection


• After clicking on Next, the units and range can be defined. The range can be left to be automatic or it can be customised by selecting the tick box.

Range and units for maths channel.png
Range and Units for your Maths Channel


• The next screen that appears summarises the actions taken. The Finish button has to be selected at this stage to save the settings unless further editing is required.

finish.png
Creation Process Complete


• When finished, the newly created Maths channel appears in the Library and can be enabled by clicking the tick box and then selecting OK:

Library.jpg
Library
Library.jpg (22.89 KiB) Viewed 4121 times


• The signal below shows a very noisy sinewave. PicoScope averages the signal over a number of buffers and cleans up the signal dramatically.

noisy sine wave step6.png
Sinewave


• The image below shows the peak (also called envelope) taken from a signal that is sweeping up and down in frequency. This takes the min and max pairs and draws a line between them. The peak measurement is the same as drawing a line between the min and max measurements. This mode is useful for analysing jitter on a signal.

averaged + peak hold -- step 7.png
Multiple views


Have fun and as always we are here to help.

Kindest regards,

Stuart
Applications Engineer
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Re: Waveform averaging - the PicoScope way

Postby F4CTZ » Fri Sep 25, 2015 4:56 pm

Hello,

I'm currently using a 5244B and the averaging function would be very very helpful if I can use it on the FFT.

Indeed, the averaging would help me lowering the noise floor of the picoscope.

Is it possible in the actual version. If yes, how to do it because I'm unable to see spectrum from a mathematical channel like Average(A).

Thanks for the help,
Best Regards,
Fabien.
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Re: Waveform averaging - the PicoScope way

Postby Martyn » Mon Sep 28, 2015 11:06 am

Not sure if this approach would help but may be worth trying.

Set the scope running in time domain, at 200ms/div, then right click on the display and select AddView, and chose spectrum. You will now have a second view of the data in a frequency domain plot, but using the time domain data.

The time domain window is controlling the data collection, so if you now if you click on the time domain window, so that it has focus, and then use the Channel Settings, you have the option to add Resolution Enhancement which will help to reduce the noise floor. The spectrum window is calculated on the collected data so this will also reflect the reduced noise floor.

You may need to play around with the timebase and number of samples to get the correct spectrum range, as well as Tools->Preferences->Sampling to change the transition time so that data is collected in block mode, not streaming.
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Re: Waveform averaging - the PicoScope way

Postby jcapek » Tue Nov 10, 2015 5:09 pm

Hello,

I am trying to set the averaging function of waveforms by following the instructions here. The resulting waveform is really nicely smoothed, but it seems the level of averaging is independent of the number of samples in the buffer. Even if I set only one picture in the buffer, the resulting curve is nicely smoothed.

I need a possibility to set the number of waveforms for averaging. Is there any way to do this?

Thank you very much for your help.

Jiri
(Picoscope 6403C)
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Re: Waveform averaging - the PicoScope way

Postby Martyn » Fri Nov 13, 2015 1:33 pm

When using the Maths Channel Average it performs a continuous running average, including the waveforms that have been overwritten by newer ones, not a running average of the waveforms in the buffer. This additional functionality has been requested of the development team although not currently added into the software.

There is a workaround by trying Tools->Alarms, changing from Capture to BuffersFull, then adding a new alarm action to Stop Capture.

When you run the scope it will now stop once the buffers are full, and the Maths Channel average will be for the stored buffers.
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Re: Waveform averaging - the PicoScope way

Postby jdepalma » Thu Jan 07, 2016 4:50 pm

Hi Martyn,

I have as question about saving the average waveform. I followed the above instructions for the work around to stop collecting after the buffers were full - I set it to collect 128 scans in the buffer. I am relatively new to Pico. I went to try and save the average, and when I did, I did not realize that it was saving 128 different files!

Is it possible to only save the 128-scan average as a single file? Or, how do I average all the files together? Thanks in advance.
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Re: Waveform averaging - the PicoScope way

Postby Martyn » Fri Jan 08, 2016 8:36 am

Use Save Current Buffer, which will just save the last one.
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Re: Waveform averaging - the PicoScope way

Postby jdepalma » Fri Jan 08, 2016 1:10 pm

Hi Martyn,

Thanks for the tip! I have another question for you about averaging.

The physical oscilloscope attached to my instrument has the option to run in sample mode OR run in average mode, where I can take the summed average of 4, 16, 64 or 128 individual shots to make nice looking spectra. In other words, if I set oscilloscope to average four acquisitions, then it will average each new acquisition into the total average displayed on the screen, as it is acquired. When it gets the fifth acquisition, it discards the average information created by the first acquisition, and adds the fifth to the total average. When you get the sixth acquisition, it discards the second and adds the sixth, and so on. Is this possible in the your software? I tried to figure it out (and do did my boss) but we were unable to figure it out. Is this possible?

In additionally, I am currently writing LabView software to take the same spectra I described above. I have written a VI that can read the 5444A's output in real time, display a live waveform, and then average as many spectra as I desire. This is OK, but I am looking to do the same binned continuous averaging I described above. Do you have any sub-VI's which do this, or could you point me in the correct direction?

Any help is appreciated. Thanks.
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Re: Waveform averaging - the PicoScope way

Postby Martyn » Tue Jan 12, 2016 8:16 am

The rolling average of the waveform buffers, discarding the oldest and adding the newest,is a feature request for our PicoScope software already, although I have no timescales as to when/if this will be implemented.

We don't have any Vi's that will do this, I would look to have a rolling set of buffers that you load the live data in to, and then average these. In this way you can initiate the collection of new data to the live running buffer whilst performing the averaging of the last x buffers.
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