PicoScope Beta 6.9 Beta New Filter Options

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Steve Smith
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PicoScope Beta 6.9 Beta New Filter Options

Post by Steve Smith » Thu May 22, 2014 3:39 pm

Beta releases have NOT been fully tested by us. If you choose to install and use the beta software you should expect to run into bugs. These bugs may range in severity from minor features that don’t work to problems that may cause your PC to crash.

This forum post is intended to provide a brief introduction to a new feature prior to full instructions being added to the manual. If you have any questions / comments about its use (including just wanting to thank the developers for adding the feature :D) then please post below.

Most PicoScope oscilloscopes have both hardware-based low pass filters (bandwidth limiters) and software-based low pass filters (digital filters). Each type of filter has different advantages and disadvantages that are described in the manual. These filters can be used independently or combined for maximum flexibility.

As low pass filters are the ones most commonly used, they are available in the channel options as shown below:
In PicoScope 6.9.5 we have added more digital filters (high pass, band pass etc.) and made them available as maths channels. The advantage of using maths channels is that you can now display the original (unfiltered) waveform at the same time as the filtered waveform. In the example below I have used a sine wave exhibiting noise (Cha A Blue) whilst the maths channel below (Black) provides a filtered version of the same sine wave with the noise removed.
To use these new functions follow these steps:

1. Create a new maths channel (Tools > Maths Channels > Create)

2. Select Advanced in the maths channel "Equation Editor" and on the left choose the filters option. You then have a choice of

* High pass
* Low pass
* Band pass
* Band stop
You can select the filter type using the relevant filter buttons (in the example above "LowPass"), then select the channel and frequency in Hz. The correct format for a 10 Hz low pass filter on channel A is as follows:

LowPass(A,10) as with the example waveform above.

This feature will provide ideal protection from the pitfalls of over-filtering given you can see the "before and after" effects of the amount of low pass filter applied to the original waveform. O2 sensors spring to mind due to the vulnerability of the low frequency, low voltage signal in the typical harsh environment of an engine bay.

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Re: PicoScope Beta 6.9 Beta New Filter Options

Post by FioranoCars » Sun Jan 31, 2016 3:31 pm

Hi Steve
Just been playing in offline mode with a few waveforms from last weeks work, and noticed a few things while trying to play with Maths Channel Filtering. I had a particular need to keep the raw signal and also display a filtered version, so this feature was perfect, and allowed me to get exactly what I wanted ... but a few thoughts and ideas from my toying ... I'll stick to using the phase "offline" for saved captures without scope attached, not sure, if with a scope attached, it would change any of these issues ... as scope is at work!

Anyway, as it's nearly 2 years since these things were introduced, here are some comments, well apart from "keep the improvements coming" and "continue to provide an amazing product and great support environment"!

1. Being able to play and modify settings and filters 'Offline' after the fact and see them applied without a scope connected is essential, so thanks for this, can you keep as many features and tools usable without the scope attached, while not devaluing/loosing your Intellectual Property which is clearly huge!
2. With 'Offline' waveforms, some settings cannot be changed, like time base, when in reality it's not hard to achieve that (increasing or reducing the number of buffers/pages),
3. where as the capture rate I understand is fixed!! BUT does it need to be? Applying a lower rate (reducing file size ~ tweaking templates) would be a useful addition, to see how low a rate you can use without loosing the detail needed, so that would be nice to have too!
4. Ignore this - re-read the help file!! Loaded Probes verse Library! ... But where are the custom "Library" Probes and Maths items stored? It was easy in WinXP, but Win7x64 can't seem to find them? Still looking!
5. When making changes to Channel settings, the filter/resolution (12-16bit) are applied in real time, allowing tweaking to achieve the desired result ... While with maths channels, the changes are not applied until you leave the Maths Channel menu ... Please can we have an "Apply" button in the equation editor screen to allow rapid trial and error/tweaking/playing. You have a real time error checker (flashes a red x), so maybe even apply each time you type? (maybe a preview check box to avoid excess CPU load, defaulted to off)?
6. The Filters Options have tooltips showing the formulae syntax, however none of the other advanced elements have these ... can they be added?
7. The help files for advanced items are missing examples or detailed explanations ... Maybe adding links to more advanced topics/articles on the website, like this article allowing quick and easy access to more help ?
8. There is at the end of the channel list a drop down, it's pretty "hidden" ... maybe this could be given more prominence... in my blinkered past, I've never noticed this, not played with it yet, but will shortly!
9. There are two (or more?!) features not shown on the editor screen, Sign() and [t], can these be added and tool tips along with them?

and finally ...
10. Any chance of a more detailed and advanced filtering tutorial, with a compare and contrast to the Channel settings equivalent filter/resolution options Verse the Maths Channel options? Especially the Pro's and Con's of multi filtering and ordering of the filters etc, go on, please!

Hope it's useful feedback?
Ricahrd Lukins

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