Frequency Response Analyzer with Bode Plots

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ts8051
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Re: Frequency Response Analyzer with Bode Plots

Post by ts8051 »

Hello,
If you trying to develop a new frequency response analyzer tool, is it possible to compile it for macos? I will test it and make a report.

hexamer
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Re: Frequency Response Analyzer with Bode Plots

Post by hexamer »

Nicosten wrote:
Thu Feb 04, 2021 8:09 am
Dear all,

Can you recommend an external amplifier to insert after a PicoScope 5000D generator output (+/-2V into 50 Ohms) that can provide +/-10V into high impedance with possibility to add a bias voltage +/-5VDC ?
Many thanks in advance.
If you don't need it to do extreme things like drive a highly capacitive load or cover the full bandwidth of 20 MHz, what you're looking for is very easily achieved with a summing op-amp circuit on a breadboard (https://www.electronics-tutorials.ws/opamp/opamp_4.html). One input could be tied to a potentiometer in a voltage divider configuration to control offset and the other input used to amplify the scope's signal generator output.

If you don't mind some peaking in the output response, you can drive capacitive loads up to a reasonable level (maybe a few dozen or even hundred pF if you're lucky) with many op-amps before they become completely unstable. The difficulty with covering up to 20 MHz is that with 5x gain, you'll need an op-amp with fairly high GBW. Such op-amps don't often perform well (become unstable) with all the parasitics on a breadboard.

If you decide to go this route, pick an op-amp with wide supply capability. To get the signal you want, you'll probably need at least +/- 12 V supply. Then pick an op-amp with not alot more GBW than you need. You'll often see that some voltage feedback op-amps with high bandwidth have minimum gain requirements. So you may end up with a 10x amplifier instead of 5x. Based on a quick seach, these options which seem to come in PDIP packages might work to achieve 20 MHz: LM7171, LT1222. If you really don't need that much bandwidth, you can probably get away with a much more mainstream op-amp.
Last edited by hexamer on Mon Feb 22, 2021 8:06 pm, edited 1 time in total.

hexamer
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Re: Frequency Response Analyzer with Bode Plots

Post by hexamer »

I am happy to announce a new release of FRA4PicoScope: https://bitbucket.org/hexamer/fra4picos ... 0.7.3b.msi

The primary new features are:
  • Add support for new PicoScope 6000E models (PS6824E, PS6424E, PS6804E, PS6404E, PS6403E)
  • Add support for new PicoScope 4000A models (PS4x24A)
  • Real time plotting - Plots the Gain and Phase while the FRA is running. Useful to detect if something went wrong before much time has elapsed.
  • Fixed resolution mode and choice between fixed/auto resolution for FlexRes scopes
  • Add Demo scope so users can try out the application without a scope. To access, start the app with no scope connected. Requires CPU/Platform support of AVX2 instructions.
Full details, including a list of bugs fixed, can be found here: https://bitbucket.org/hexamer/fra4picos ... %20History

Thanks a ton to Trevor and Martyn at Pico for all their help!
Last edited by hexamer on Wed Feb 24, 2021 1:59 am, edited 1 time in total.

Nicosten
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Re: Frequency Response Analyzer with Bode Plots

Post by Nicosten »

Hi Aaron,
I have installed the latest version 0.7.3b, assuming I could use it without a scope ( as described in your notes). Unfortunately, the program does not start at all. I am using Windows 10 - 64 bit. The Picoscope application is already installed. Is it normal ?

hexamer
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Re: Frequency Response Analyzer with Bode Plots

Post by hexamer »

Nicosten wrote:
Mon Feb 22, 2021 2:07 pm
Is it normal ?
I hope not :)

I have a suspicion of what's going on here though. For some reason the popup asking you whether you want to use the demo scope does not come to the foreground, so it may look like the application is not running. If you Alt-Tab, do you see it?

If this isn't your problem, here are some other things to check:

1) Make sure you have the 32-bit version of SDK 10.7.20.192
2) Do you have AVX2 instruction support on your system - this shouldn't affect whether the program launches, but is a prerequisite for using the demo mode scope.

Nicosten
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Re: Frequency Response Analyzer with Bode Plots

Post by Nicosten »

Hi Aaron,
After havving installed the 32-bit version of SDK 10.7.20.192, it now works !
Thanks a lot for your help.
Best regards.

Nicosten
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Re: Frequency Response Analyzer with Bode Plots

Post by Nicosten »

Hi Aaron,

I have pushed my curiosity a little bit and tried to export the data to CSV and graph them with Excel.
It seems the X values are powers of 10, but I don't understand the Y values for Gain in dB.
The values start with -0.5 dB down to -35 dB but the shape is inverted. I have attached the files, could you please explain?
Attachments
FRA_passebas3KHzExcelscreen.gif
PasseBas3KHz.csv
(12.67 KiB) Downloaded 149 times
PasseBas3KHz.png

hexamer
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Re: Frequency Response Analyzer with Bode Plots

Post by hexamer »

Nicosten wrote:
Tue Feb 23, 2021 3:27 pm
Hi Aaron,

I have pushed my curiosity a little bit and tried to export the data to CSV and graph them with Excel.
It seems the X values are powers of 10, but I don't understand the Y values for Gain in dB.
The values start with -0.5 dB down to -35 dB but the shape is inverted. I have attached the files, could you please explain?
Nicosten,

Since the FRA application is graphing frequency on a log scale Log (Hz), to match the shape, you'll also have to tell Excel to use a log scale for the x-axis. See attached.

Thanks,

Aaron.
Attachments
PasseBas3KHz.xlsx
(37.31 KiB) Downloaded 145 times
PasseBas3KHz.jpg

Nicosten
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Re: Frequency Response Analyzer with Bode Plots

Post by Nicosten »

Hi Aaron,
Understood, thank you for your excellent support!
Best regards,
Nicosten

yosi
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Re: Frequency Response Analyzer with Bode Plots

Post by yosi »

Hi, I need your help.

I have read a few tens of messages on this forum, but could not find help,
excuese me if I overlooked.

FRA4PicoScope.exe does not start on my Windows 10 PC.
What can I do to use this great software ?
Should I try older vesion ?
I know FRA4 a few days ago, I hope and wish to use it.

When I clicked FRA4-icon, it just quit, no messages.
Looking into eventviewer, I found some error mighte be happened in Kernel.DLL
The event log says,

event : APPCRASH
Response: Not available
Cab ID: 0
P1: FRA4PicoScope.exe
P2: 0.0.0.0
P3: 6032d480
P4: KERNELBASE.dll
P5: 10.0.19041.804
P6: b610d74d
P7: c06d007f
P8: 0012a8b2
P9:
P10:

I'm using picoscope 3206B, softwere version 6.
Pico Technology's PicoScope 6 App runs fine on my PC.
I have installed PicoSDK 32bit 10.7.20.192 Just before FRA4PicoScope_0.7.0b.msi.

I wonder .. maybe some API is required which is not available on my PC.
Oh, OS version is ' Windows 10 Home, 10.0.19041 build 19041'
CPU: Intel Core i5-7500, Memory: more than 12Gbytes available.

Thanks in advance.

hexamer
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Re: Frequency Response Analyzer with Bode Plots

Post by hexamer »

yosi,

Thank you for reporting this. I hope I can help. Here are a few thoughts:

1) I noticed that you say you installed v0.7.0b, whereas v0.7.3b is the version compatible with PicoSDK 32bit 10.7.20.192. If you really have installed v0.7.0b, please install the latest (v0.7.3b) and try again. Otherwise ...

2) Just in case the APPCRASH was something transient, I'll mention that there is a "bug" in the released version where it can appear as if it's not running but it actually is. However, for this to be the case, it has to fail to open your scope, then detect that your computer is compatible with demo mode (has AVX2 support). Since your scope should be supported (and I've not tested that scope), and your CPU has AVX2, this may be what's going on. To tell, launch the application and wait about 30 seconds or so - or until all the PicoScope splash screens stop appearing. Did you get the momentary PicoScope splash screens? Once you've given it enough time to fully load, either Alt-Tab to see if you can find the dialog that's prompting you whether you want to use demo mode, or bring up the task manager to see if the FRA4PicoScope.exe is still running.

3) If the APPCRASH is really happening every time you launch, I did find some info suggesting that it could be due to a user profile corruption. Does the application crash if you login as a different user?

4) If none of the above work, I can build you a debug version that might help give us some more clues. Please let me know as I'd like to get this fixed in case anyone else is having similar issues.

Thanks,

Aaron.

yosi
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Re: Frequency Response Analyzer with Bode Plots

Post by yosi »

Dear Aaron, Thanks a lot !

I could managed to fix.
When I installed PicoscopeSDK, I unselected Ps6000x devices.
That seems to be the reason of this problem.

First, I uninstall and re-install v0.7.3b of FRA4. -- nothing changed.
Next, signed in as different user, and try -- same, no change.

As to your suggestion '2)' , I could not figure out what you meant acturally,
because I 've never seen FRA4's splash screen at that time.
I thought you mean picotech's Picoscope application, and questioned why?
I have installed FRA4 into windows 7 environment, and knew FRA4 splash screen.

Then to make things clean, I reinstalled both FRA4 and SDK, that worked.
After mean time, I remember that I might disabled Ps6000a device.

Thanks again.

hexamer
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Re: Frequency Response Analyzer with Bode Plots

Post by hexamer »

Thank you, yosi, for reporting back. Since this:
yosi wrote:
Sat Mar 27, 2021 5:29 am
When I installed PicoscopeSDK, I unselected Ps6000x devices.
seems like a completely reasonable thing to do, I'll see if I can replicate. If I can, I'll work on improving the application so it doesn't crash and offers a better diagnostic.

hexamer
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Re: Frequency Response Analyzer with Bode Plots

Post by hexamer »

yosi wrote:
Sat Mar 27, 2021 5:29 am
Dear Aaron, Thanks a lot !

I could managed to fix.
When I installed PicoscopeSDK, I unselected Ps6000x devices.
That seems to be the reason of this problem.

First, I uninstall and re-install v0.7.3b of FRA4. -- nothing changed.
Next, signed in as different user, and try -- same, no change.

As to your suggestion '2)' , I could not figure out what you meant acturally,
because I 've never seen FRA4's splash screen at that time.
I thought you mean picotech's Picoscope application, and questioned why?
I have installed FRA4 into windows 7 environment, and knew FRA4 splash screen.

Then to make things clean, I reinstalled both FRA4 and SDK, that worked.
After mean time, I remember that I might disabled Ps6000a device.

Thanks again.
Well, I'm happy you got it working :), but I can't really tell what was going on. I tried re-installing the SDK without PS6000a and ps6000 support, but can't get it to crash. Only other thing I can think of that may be relevant is what version of the Picoscope app you had installed. The FRA app is setup to delay load the DLL files in order to implement a preference for the versions from SDK folders first. If it fails to load those, it can load DLLs from the Picoscope app. If there were some kind of incompatibiity there maybe it would cause an issue.

GJA14
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Re: Frequency Response Analyzer with Bode Plots

Post by GJA14 »

I'm looking to do loop gain and phase Bode plots on SMPS with switching frequency 100Khz or less. Are the 2204A and 2205A capable of doing adequate FRA plots for the above scenario or is it necessary to go up to higher models with higher sample rates, memory depth, and resolution and if so what are the minimum scope specifications needed for the above case?

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