Frequency Response Analyzer with Bode Plots

[TanTAH]

Hi all,
Please help me config for FRA test:
I want to make FRA with bode plots of control loop system, I try with PICO 2405A.
+ About my system required to test:
- AWG signal: Sine wave or White noise; Frequency range = 0.05 to 3Hz with step = 0.05Hz, Voltage = 2V.
- Input of Chanel B: AC.
+ Question need your help:
- How to setting in "FRA For PicoScope" application because as my setting it take long time to finish (picture attached)
- What is recomment parameter setting in "FRA For PicoScope" application for my test.
- What is type of AWG when we click "GO" for test because in "FRA For PicoScope" no have chooise sin wave or white noise or anything else.

Thank you very much!

[cykeltur]

Hi
i have installed 8b version:
FRA4PicoScope_0.8.0_beta.msi

I have the PS 3205A, and
when I connect it to the pc (and see the red light)
then start the FRA sorfware.
The software state it doesent find the HW.
then in the program it state in yellow text:
Status: PSDEMO S/N: PS-DEMO-001 successfully initialized.
WARNING: Unable to load SDK for PicoScope Families: PS2000, PS2000A, PS3000, PS3000A, PS4000, PS4000A, PS5000, PS5000A, PS6000, PS6000A

please help

[hexamer]

Hi all,
Please help me config for FRA test:
I want to make FRA with bode plots of control loop system, I try with PICO 2405A.
+ About my system required to test:
- AWG signal: Sine wave or White noise; Frequency range = 0.05 to 3Hz with step = 0.05Hz, Voltage = 2V.
- Input of Chanel B: AC.
+ Question need your help:
- How to setting in "FRA For PicoScope" application because as my setting it take long time to finish (picture attached)
- What is recomment parameter setting in "FRA For PicoScope" application for my test.
- What is type of AWG when we click "GO" for test because in "FRA For PicoScope" no have chooise sin wave or white noise or anything else.

Thank you very much!

Hello TanTAH,

Thank you for your questions. Without understanding the system you're trying to measure, it's difficult to advise on every setting, but I understand you have two primary concerns (duration and stimulus type). I'll explain them in reverse order because the answer to the second one may make the first one easier to understand

1) The FRA Application works on the principle of a swept (stepped) frequency sinusoidal stimulus. It turns on the AWG at specific frequency, then attempts to capture an integer number of cycles, then performs a DFT at that frequency to measure I/O amplitude and phase. I know there are FRA methods of injecting broadband stimulus to a system (e.g. step or impulse), then applying a frequency transform to measure the I/O response. However the FRA application was not designed this way, so there is no such option to set the AWG output type.

2) The duration of the full sweep in your case is largely driven by the low frequencies you use and the "Minimum cycles captured" setting. That setting controls exactly how many stimulus cycles are captured. So, at 0.05Hz, a single capture takes 20 seconds * 16 cycles => 320 seconds. Then, with auto-ranging needing to repeat that until it finds the optimal range, it will take longer. The simplest way to speed it up is to change "Minimum cycles captured" to something lower (all the way down to 1 if necessary). You could lose some SNR, but it may not be noticeable.

Thank you,

Aaron

[hexamer]

Hi
i have installed 8b version:
FRA4PicoScope_0.8.0_beta.msi

I have the PS 3205A, and
when I connect it to the pc (and see the red light)
then start the FRA sorfware.
The software state it doesent find the HW.
then in the program it state in yellow text:
Status: PSDEMO S/N: PS-DEMO-001 successfully initialized.
WARNING: Unable to load SDK for PicoScope Families: PS2000, PS2000A, PS3000, PS3000A, PS4000, PS4000A, PS5000, PS5000A, PS6000, PS6000A

please help

Hello. The WARNING message is indicating that there is no SDK installed

Please install the latest Pico 32-bit SDK: https://www.picotech.com/download/softw ... 26.362.exe before running the application

Thank you, Aaron.

[rotalumis]

Hi there,
I have a Picoscope 4262 and FRA works flawlessy. Trying with my other Picoscope, a 4227, while succesfully initialized, gives me three errors, one after the other:
1) Fatal error: Failed to determine sample buffer size: 14
2) Fatal error: Unable to determine minimum stimulus frequency. Unable to determine maximum samples.
3) Error: Invalid inputs.

I'm really baffled of what to do. Any clue?

[hexamer]

Thank you for reporting this issue. If you don't mind, could you provide me a diagnostic trace? Go into Tools -> Settings -> Log Verbosity and check PicoScope API Calls. Then restart the app with your PS4227 attached. You should get a lot of very detailed information in the log. Please post it here and we should be able to get to the bottom of this.

Thank you,

Aaron.

Hi there,
I have a Picoscope 4262 and FRA works flawlessy. Trying with my other Picoscope, a 4227, while succesfully initialized, gives me three errors, one after the other:
1) Fatal error: Failed to determine sample buffer size: 14
2) Fatal error: Unable to determine minimum stimulus frequency. Unable to determine maximum samples.
3) Error: Invalid inputs.

I'm really baffled of what to do. Any clue?

[rotalumis]

Thank you, attached is the screen print of the verbose log. I might add that I couldn't go to Tool -- > Settings in the menu when the 4227 was connected, the program would just exit without notice. Instead, I attached the other Picoscope (the 4262), enabled the verbose log and then close the program, switch the two scopes... and here we are.

[hexamer]

Thank you for getting back with me. The API trace log is showing that an invalid timebase of 0 is being passed to ps4000GetTimebase. The PS4227 supports timebase 0 but only when a single channel is enabled (which is inconsistent with FRA). So, this is a bug in the FRA application. I will work on fixing this in the next release. But I can give you an interim version if you'd like to help me confirm the fix works. Thanks again for helping out!

[rotalumis]

Of course I will happy to test the fix, I'm the one to thank you!

Thank you for getting back with me. The API trace log is showing that an invalid timebase of 0 is being passed to ps4000GetTimebase. The PS4227 supports timebase 0 but only when a single channel is enabled (which is inconsistent with FRA). So, this is a bug in the FRA application. I will work on fixing this in the next release. But I can give you an interim version if you'd like to help me confirm the fix works. Thanks again for helping out!

[hexamer]

Of course I will happy to test the fix, I'm the one to thank you!

Here you go: https://bitbucket.org/hexamer/fra4picos ... 2_Test.msi

Please let me know if this fixes the issue and I'll get the fixes into the next release.

[rotalumis]

Almost there... and the program does not exit when going to Tools -- > Settings

[hexamer]

Whoops looks like I broke something else. It didn't get as far this time. Would you mind posting the text of the log here. In the screenshots some of it is not showing.

[rotalumis]

Sure, here it is

ps4000OpenUnitEx( 004FE8CC, 004FE93C );
ps4000GetUnitInfo( 16384, 004FE7C4, 32, 004FE7A4, 3 );
ps4000MemorySegments( 16384, 1, 004FE7A8 );
ps4000GetUnitInfo( 16384, 004FE91C, 32, 004FE8FC, 3 );
ps4000GetUnitInfo( 16384, 004FE91C, 32, 004FE8FC, 4 );
Status: 4227 S/N: AR290/148 successfully initialized.
ps4000GetUnitInfo( 16384, 004FE6D4, 32, 004FE6B4, 3 );
ps4000GetUnitInfo( 16384, 004FE6D4, 32, 004FE6B4, 4 );
ps4000GetUnitInfo( 16384, 004FE91C, 32, 004FE8FC, 3 );
0 <== ps4000PingUnit( 16384 );
ps4000SetChannel( 16384, 0, 1, 0, 2 );
ps4000SetChannel( 16384, 1, 1, 0, 2 );
Fatal error: Unable to determine minimum stimulus frequency. Unable to determine sampling frequency.
Error: Invalid inputs.

[hexamer]

Thank you for the extra information. After reviewing the updated code and confirming that it's correct, I believe what's probably happening here is that your trying to use noise reject mode, and the earlier invalid timebase of 0 got latched into the scope settings file. To fix that:

Close the app, delete the scope settings file, then reopen the app to re-build it. The scope settings file should be located here: C:\Users\[User Name]\AppData\Roaming\FRA4PicoScope\Fra4PicoScopeSettings_4227_AR290_148.xml

[rotalumis]

Indeed that was the problem, deleting the file cleared the issue! Many thanks for your time, great support and dedication toward (above all) a free app!