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Frequency Response Analyzer with Bode Plots

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Re: Frequency Response Analyzer with Bode Plots

Postby hexamer » Wed Jul 26, 2017 12:32 pm

Andreas_ wrote:Hello Aaron,

im using the 5444A.

My 2nd question was not to turn off the whole numbering of the axis.
I do simply not want 2 same numbers on different places on the y-axis.
So I need either a further digit (-41.15) or leaving off every 2nd number of the y-axis.
Otherwise the Y-axis numbering is somewhat confusing.
(see attachment).

with best regards

Andreas


Andreas,

Thank you for the clarification. A picture is worth 1000 words! I can't immediately think of a clever solution to what I think is really a fundamental problem. E.g. you can continue to zoom in such that the axis span is even smaller. In such case the axis labels would have more significant figures than would fit on the graph.

Thank you,

Aaron.
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Re: Frequency Response Analyzer with Bode Plots

Postby Martyn » Wed Jul 26, 2017 1:07 pm

In the example you could reference against -40 and then just display the offset from this.

Take a look at the way the PicoScope 6 software handles zooming in so that you always display 4 relevant digits.
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Re: Frequency Response Analyzer with Bode Plots

Postby hexamer » Wed Jul 26, 2017 1:30 pm

Martyn wrote:In the example you could reference against -40 and then just display the offset from this.

Take a look at the way the PicoScope 6 software handles zooming in so that you always display 4 relevant digits.


Thank you Martyn. I'll take a look. If I understand you correctly, to handle the general case, the base/reference number carries some number of the significant digits. So, techniques like that (including use of scientific mode) can help, but would still have a limit. So I guess it's a matter of how much more precision to be able to show.
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Re: Frequency Response Analyzer with Bode Plots

Postby mrtl » Tue Aug 08, 2017 10:01 am

Hi Aaron,

we would like to use the PicoScopes instead of Velleman equipment for our practical student curses in the future. Because of this, the FRA (Bode Plot) is very important for us.

Unfortunately i get the same error than Martin.S, when using a PicoScope 3203D:
Status: 3203D S/N: ES292/096 successfully initialized.
Status: Starting frequency step 1 (9.998 Hz)
...
Status: Starting frequency step 31 (10000.002 Hz)
Fatal error: Failed to setup stimulus signal: 46
Error: Failed to disable signal generator.

I already installed the 32-bit SDK, but without success.

Kind regards
Bernhard
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Re: Frequency Response Analyzer with Bode Plots

Postby hexamer » Tue Aug 08, 2017 10:14 pm

mrtl wrote:Hi Aaron,

we would like to use the PicoScopes instead of Velleman equipment for our practical student curses in the future. Because of this, the FRA (Bode Plot) is very important for us.

Unfortunately i get the same error than Martin.S, when using a PicoScope 3203D:
Status: 3203D S/N: ES292/096 successfully initialized.
Status: Starting frequency step 1 (9.998 Hz)
...
Status: Starting frequency step 31 (10000.002 Hz)
Fatal error: Failed to setup stimulus signal: 46
Error: Failed to disable signal generator.

I already installed the 32-bit SDK, but without success.

Kind regards
Bernhard


Hi Bernhard,

Can you confirm whether you are able to produce a Bode plot that looks as expected?

The error messages you show (despite their ominous wording) are harmless. Since this topic tends to come up fairly often, let me try to explain some more details:

A while back it was reported that after a FRA run the signal generator remains active at the last tested frequency. I attempted to resolve this problem, but there is no unified SDK API to disable the signal generator. So I tried to do the next best thing and set the signal generator to 0V, 0 Hz. I set it to 0Hz, because on the PS3000 SDK that should disable the signal generator. Unfortunately that input combination on other scope family SDKs results in an error returned by the API, which the FRA application reports. In general (throughout the actual FRA execution), failing to set the signal generator should be a "fatal error" because the FRA would not be correct. In the case of attempting to disable the signal generator, it should not be fatal because the result is just that the signal generator remain on.

I had been waiting on an API enhancement to fix all of this, but it's not available yet. topic14569.html

Thank you,

Aaron.
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Re: Frequency Response Analyzer with Bode Plots

Postby Andreas_ » Fri Aug 11, 2017 6:57 pm

Hello Aaron,

don´t know wether you have a PS4824 in your compatibility list.
Today I could do a quick check at the device from work.

I also have the error code 46 on this device.
But the bode plot looks to be ok.
Compared to the PS5444A-plot some days ago.

With best regards

Andreas
Attachments
20170811_Divider_100K_1K_3Hz_300kHz_4V_PS4824_3rd_run.PNG
PicoScope 4824 checked with 100K/1K divider
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Re: Frequency Response Analyzer with Bode Plots

Postby hexamer » Mon Aug 14, 2017 12:30 pm

Andreas_ wrote:Hello Aaron,

don´t know wether you have a PS4824 in your compatibility list.
Today I could do a quick check at the device from work.

I also have the error code 46 on this device.
But the bode plot looks to be ok.
Compared to the PS5444A-plot some days ago.

With best regards

Andreas


Thank you for the update, Andreas. It's very helpful to know which scopes are compatible.
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Re: Frequency Response Analyzer with Bode Plots

Postby mrtl » Mon Aug 14, 2017 12:58 pm

hexamer wrote:
mrtl wrote:Hi Aaron,

we would like to use the PicoScopes instead of Velleman equipment for our practical student curses in the future. Because of this, the FRA (Bode Plot) is very important for us.

Unfortunately i get the same error than Martin.S, when using a PicoScope 3203D:
Status: 3203D S/N: ES292/096 successfully initialized.
Status: Starting frequency step 1 (9.998 Hz)
...
Status: Starting frequency step 31 (10000.002 Hz)
Fatal error: Failed to setup stimulus signal: 46
Error: Failed to disable signal generator.

I already installed the 32-bit SDK, but without success.

Kind regards
Bernhard


Hi Bernhard,

Can you confirm whether you are able to produce a Bode plot that looks as expected?

The error messages you show (despite their ominous wording) are harmless. Since this topic tends to come up fairly often, let me try to explain some more details:

A while back it was reported that after a FRA run the signal generator remains active at the last tested frequency. I attempted to resolve this problem, but there is no unified SDK API to disable the signal generator. So I tried to do the next best thing and set the signal generator to 0V, 0 Hz. I set it to 0Hz, because on the PS3000 SDK that should disable the signal generator. Unfortunately that input combination on other scope family SDKs results in an error returned by the API, which the FRA application reports. In general (throughout the actual FRA execution), failing to set the signal generator should be a "fatal error" because the FRA would not be correct. In the case of attempting to disable the signal generator, it should not be fatal because the result is just that the signal generator remain on.

I had been waiting on an API enhancement to fix all of this, but it's not available yet. topic14569.html

Thank you,

Aaron.


Hi Aaron,

i made a small electric circuit with a resistor an a condenser in series connection.
With the Velleman i get a correct diagram, but not with the PicoScope.
Just look at the below pictures.
Velleman.JPG
Velleman

PicoScope.JPG
PicoScope


Kind regards Bernhard
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Re: Frequency Response Analyzer with Bode Plots

Postby hexamer » Tue Aug 15, 2017 1:58 am

mrtl wrote:Hi Aaron,

i made a small electric circuit with a resistor an a condenser in series connection.
With the Velleman i get a correct diagram, but not with the PicoScope.
Just look at the below pictures.
Velleman.JPG

PicoScope.JPG


Kind regards Bernhard


Bernhard,

Thank you for the clear response. I am not too familiar with the Velleman Bode plotting feature, but having read their manual, I noticed that their system does not require feeding back the stimulus signal into a scope channel. If you were trying to use the FRA4PicoScope application in the same way, it would not work. The proper way is to connect the PicoScope's signal generator (AWG) in parallel to the "circuit under test" input and a first oscilloscope channel - and connect the "circuit under test" output to a second oscilloscope channel.

Thank you,

Aaron.
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Re: Frequency Response Analyzer with Bode Plots

Postby mrtl » Tue Aug 15, 2017 12:58 pm

Hi Aaron,

many thanks for this great help. Thats how it works.
If I export the data from your software and adjust the axes accordingly in Excel (linear instead of logarithmic or db), this results in the same diagram as in Velleman (see pictures).
Best regards

Bernhard
Attachments
Excel.JPG
Excel-Import
PicoScope.JPG
PicoScope
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