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MSO5000 Bode Plot Capability: Is it Good Enough? [Many tips about a 1st scope]

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2N3055:

--- Quote from: balnazzar on October 09, 2022, 01:22:59 pm ---
--- Quote from: 2N3055 on October 09, 2022, 11:53:59 am ---Most of them support Hexamers FRA application, but not lowest 2000 models. Not all models are available now.

--- End quote ---

I'm trying to get more info about that. In particular, which ones are 'lowest enough' not to support the FRA app.

It seems the absolute lowest model (10 MHz) is not supported [source: pico forums, Hexamer's posts]
It is unclear if for example, the 25,50,70,100 MHz models support it.

The wiki says:
The current design of the application requires a PicoScope device that has at least 2 channels and a function generator. [...]
Some devices are not compatible due to other unique impediments. For example, the PS3204 function generator currently does not output a pure sine.

It also seems that the FRA won't work with an external function generator.

--- End quote ---

2000 series with small memory does not work. Because it has to capture large burst at a time.
Actually it works but not all the time and with all settings.. I don't remember the details.
2207B up to 2408B have 64 MB memory and they work fine for sure.
Which puts it in a almost same price bracket as smaller of 3000 series, that are better devices.

PS3204 is old discontinued device...

Interesting thing about Hexamer's FRA fro Picoscope is that full source is available. And if you look into source, signal generating part is separated in module and can be replaced with code that drives some other generator... In  fact there are preparations in code for it..

jasonRF:

--- Quote from: balnazzar on October 09, 2022, 01:22:59 pm ---
--- Quote from: 2N3055 on October 09, 2022, 11:53:59 am ---Most of them support Hexamers FRA application, but not lowest 2000 models. Not all models are available now.

--- End quote ---

I'm trying to get more info about that. In particular, which ones are 'lowest enough' not to support the FRA app.

It seems the absolute lowest model (10 MHz) is not supported [source: pico forums, Hexamer's posts]
It is unclear if for example, the 25,50,70,100 MHz models support it.

The wiki says:
The current design of the application requires a PicoScope device that has at least 2 channels and a function generator. [...]
Some devices are not compatible due to other unique impediments. For example, the PS3204 function generator currently does not output a pure sine.

It also seems that the FRA won't work with an external function generator.

--- End quote ---
The 3204 is a very old model that is out of production (EDIT: I see 2n3055 beat me to it!).  My understanding is that it works fine with most of the more modern Picoscopes.   Again, I have never had any problems using it with my 2204a.  Works every time.

And yes, only Hexamer  has written a plugin to interface with another function generator.  But the hooks are there, as 2N3055 points out.

If you want to use an external function generator to do Bode plots outside of FRA4Picoscope there are several options. 

1. Just like you can with any scope, do it the old-fashioned way and manually do the measurements frequency by frequency, then plot in your software of choice.  This is complicated by the fact that the Picoscope software does not have automated time-delay or phase-difference measurements, which is a little irritating.  You can use math channels to program your own, or you can use cursors and do it the slow way... 

2. Use the PicoSDK (software developement kit) and write you own code.  If you are using c or c++ it might take some time depending on your programming skills, but if you are happy with a simple Python script there are Python wrappers for the PicoSDK functions.   The key will be learning how to control your function generator from Python.  I have started playing with this recently, and it doesn't look bad at all to control a Picoscope and read the data, although it will probably take another couple of hours to get a simple end-to-end script to make basic plots (mostly hampered by the fact that I don't really know Python).  The only computer-controllable signal sources I have are a nanoVNA, tinySA, and an Arduino-controlled AD9833-based generator still on a solderless breadboard.  While I can control all of them just fine from Python, all just use simple commands over a COM port.  Commercial function generators may take more work to interface. 

3. Semi-automated.  For each frequency: setup the function generator and scope settings, then save the waveforms in an output file.  One file per frequency.  Then you can suck the data into your favorite software (I have done this with Octave), looping over the files to compute the gain and phase for each frequency and then generate the plot.   I have done this a number of times with my 2204a using an old 12-MHz BK Precision DDS function generator (an ebay special) that has no provisions for software control.  This approach takes some time - using keyboard shortcuts I can do about three frequencies per minute (mostly dominated by the wonky function gen interface).  I estimate the frequency as part of processing each file, so don't need to keep track of that info separately or do the frequencies in any particular order.

jason

balnazzar:

--- Quote from: jasonRF on October 09, 2022, 02:40:23 pm ---
But any 5000-series pico has 8 independent ADCs (I think that's why they can get to 16 bit resolution.. By stacking ADCs..)

Dave did a teardown of a 5000B scope a bunch of years ago (I think it was a 5443B), so I know that it has a single ADC chip that draws something like 1/2 Watt.  It is a very specialized chip, and they basically designed their scopes around it.  I suspect they use that same chip in the current 5000D series, unless it is obsolete.     

Regarding FRA4Picoscope, it works fine with my 2204a, the cheapest Picoscope in the current lineup.  For years that was my only scope and I used that app many times.  There are examples from at least two different 2000-series (including my 2204a) in the thread
https://www.eevblog.com/forum/testgear/picoscope-2000/

jason

--- End quote ---

Thanks for the information!

I was making reference to this forum post: https://www.picotech.com/support/topic14311.html
Particularly, the third post from above. Says that the 2204A has something that hinders the FRA app. Maybe it was solved in the successive software releases?

About the 5000 series, they advertise them as having eight (!) ADCs. Maybe it's just for the lastest 5000 series models?

One question about that little 10 MHz scope. How often did you hit the bandwidth limit in your work? For example, you were able to accurately observe transients up to which frequency?

Thanks!

balnazzar:

--- Quote from: 2N3055 on October 09, 2022, 02:57:10 pm ---Interesting thing about Hexamer's FRA fro Picoscope is that full source is available. And if you look into source, signal generating part is separated in module and can be replaced with code that drives some other generator... In  fact there are preparations in code for it..

--- End quote ---

That's very good news. If it's witten in Python, I have some programming experience with it.
Thanks!

balnazzar:

--- Quote from: jasonRF on October 09, 2022, 03:27:11 pm ---
If you want to use an external function generator to do Bode plots outside of FRA4Picoscope there are several options. 

[...]

--- End quote ---

Thanks a lot, very detailed reply!

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