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Frequency Response Analyzer with Bode Plots

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Re: Frequency Response Analyzer with Bode Plots

Postby Martyn » Mon Apr 18, 2016 2:52 pm

Please try with the 3406D power supply plugged in.
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Re: Frequency Response Analyzer with Bode Plots

Postby hexamer » Mon Apr 18, 2016 6:30 pm

Martyn wrote:Please try with the 3406D power supply plugged in.


Martyn, Thank you for diagnosing this!

Mark, presuming this is the issue, this post contains some more info: topic14311-90.html#p74521

I would like to make a change to allow use without power supply, but I can't guarantee when it could happen. Hopefully having the power supply connected won't be too much of inconvenience.
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Re: Frequency Response Analyzer with Bode Plots

Postby mark.didat@ge.com » Mon Apr 18, 2016 6:40 pm

Aaron,

To help out with the problem solving effort I tried installing on other machines:

Win7 64-bit
Win7 32-bit
XP 32-bit

All have the same initialization issue.

The order of setup on all was:
- install Picoscope6
- install Pico SDK 32bit
- Install FRA 053b

I also have been tring to get the Matlab SDK files to run and I have a connection error there as well. This may be a Pico SDK driver issue for the 3000 series products.

Again, appreciate the help.

Mark
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Re: Frequency Response Analyzer with Bode Plots

Postby mark.didat@ge.com » Mon Apr 18, 2016 6:53 pm

This did work!
Thank you for the help! Having the power supply plugged in is not a huge deal.

Thanks again for the support!
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Re: Frequency Response Analyzer with Bode Plots

Postby micko » Wed Apr 27, 2016 12:13 pm

Hello,

I use a new 2204A picoscope and the FRA4 0.5.3b version.
By select device I get this:
PS200 DV 037/057 available

the software works, but I get no signal at the function generator, so the plot result is not useful.

Thanks for support,
Michael
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Re: Frequency Response Analyzer with Bode Plots

Postby hexamer » Fri Apr 29, 2016 1:59 pm

micko wrote:Hello,

I use a new 2204A picoscope and the FRA4 0.5.3b version.
By select device I get this:
PS200 DV 037/057 available

the software works, but I get no signal at the function generator, so the plot result is not useful.

Thanks for support,
Michael


Michael,

Thank you for reporting an issue. When I have access to my 2204A, I can see if I can reproduce it. But I'd like to ask a couple of clarifying questions.

How are you determining that the AWG is not outputting a signal? Do you have another scope to measure it?

If you use the PicoScope Application, does the AWG work?

Thanks,

Aaron.
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Re: Frequency Response Analyzer with Bode Plots

Postby micko » Fri Apr 29, 2016 8:52 pm

Hello Aaron,
thanks for your support.

Yes, I have an other scope, a Hantek DSO5102B 100MHz. And I cannot find a signal at the AWG Port.
When I use the picoscope software, the AWG works, can see it by the picoscope and by the Hantek.

If I test a simple RC filter, the plot result is only a chaos signal between -90db and -70db or something other chaos.
I think, the result is with so less db, because there is nothing to messure when the AWG is not working.
If it is helpfull, I can load a screen of a plot.

Thanks and best regards,

Michael
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Re: Frequency Response Analyzer with Bode Plots

Postby hexamer » Sat Apr 30, 2016 2:14 pm

micko wrote:Hello Aaron,
thanks for your support.

Yes, I have an other scope, a Hantek DSO5102B 100MHz. And I cannot find a signal at the AWG Port.
When I use the picoscope software, the AWG works, can see it by the picoscope and by the Hantek.

If I test a simple RC filter, the plot result is only a chaos signal between -90db and -70db or something other chaos.
I think, the result is with so less db, because there is nothing to messure when the AWG is not working.
If it is helpfull, I can load a screen of a plot.

Thanks and best regards,

Michael


Michael,

I tested on my 2204A, and I don't see any issues. The next two thoughts I have are:

1) Could you double check the Input Signal Vpp and make sure it's not very low.

2) While the symptoms your reporting are not exactly the same, another user (Mitch) reported similarly strange results when he had an incompatible version of the SDK installed. Here's the link describing that issue: topic14311-90.html#p74511

The takeaway is that you should ensure that you have the 32 bit SDK version 10.6.10
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Re: Frequency Response Analyzer with Bode Plots

Postby kally » Tue May 03, 2016 11:51 am

Hello hexamer,

did you tried already to measure the feedback loop stability of a switching power supply?

Kind regards
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Re: Frequency Response Analyzer with Bode Plots

Postby hexamer » Wed May 11, 2016 3:43 am

kally wrote:Hello hexamer,

did you tried already to measure the feedback loop stability of a switching power supply?

Kind regards
kally


Hello Kally,

I appreciate your interest in the application for SMPS loop measurements!

I've been meaning to post some examples of such measurements, especially given the recent discussions with Mitch. Today I captured some plots from the TPS5420EVM-175 to compare to the datasheet:

Vin = 25V, Iout = 1A, 40 mV constant stimulus, 10 steps per decade, 15Hz - 200 kHz
TPS5420EVM-175 (25.0 Vin, 1000 mA Iout, 40 mV stim, 15 Hz to 200 kHz, 5-10-16, 2a).png


From the EVM Datasheet:
TPS5420 Data Sheet Bode 2.png


The current Phase Margin and Gain Margin labels are not placed intelligently, so I have to expand the frequency scale to read the computed values. They are about 49 degrees and -18 dB, pretty close to the datasheet.

TPS5420EVM-175 (25.0 Vin, 1000 mA Iout, 40 mV stim, 15 Hz to 200 kHz, 5-10-16, 1a).png


If you are trying SMPS measurements and having issues, please remember that you have to run in high noise mode for it to work. See earlier posts for instructions.

Thanks,

Aaron.
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Re: Frequency Response Analyzer with Bode Plots

Postby kally » Wed May 11, 2016 7:57 pm

Thank you hexamer for your answer! Those results look great!
Because I'm quite new to this topic I wanted to ask you, if the impedance of your injection transformer VB-1BB with 75 Ohms is no problem, because all the signal generators and oscilloscopes have 50 Ohm outputs/inputs? Is there a need of an additional adaption network?

Thank you very much in advance!
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Re: Frequency Response Analyzer with Bode Plots

Postby hexamer » Wed May 11, 2016 11:53 pm

kally wrote:Thank you hexamer for your answer! Those results look great!
Because I'm quite new to this topic I wanted to ask you, if the impedance of your injection transformer VB-1BB with 75 Ohms is no problem, because all the signal generators and oscilloscopes have 50 Ohm outputs/inputs? Is there a need of an additional adaption network?

Thank you very much in advance!


The signal generator does have 50 ohm output impedance, so I suppose this configuration will lose some signal amplitude going into the 75 ohm input of the transformer. But this isn't too important because you will need to adjust the AWG Vout anyway. The VB-1BB has very flat response over the measurement frequencies. This is fairly important because the application does not yet have any adaptive output capabilities. You could just as well make or buy a cheaper transformer to match your needs. Since the Input/Output loop response channels going into the scope are both measured at the output side of the transformer and are high impedance inputs, I don't think there is any issue there. This is a good article that explains some of these concepts: http://www.ti.com/lit/an/snva364a/snva364a.pdf

Another important point on SMPS analysis with PicoScopes is dynamic range and buffer depth. I have not tried on scopes other than PS5444A, but you may get others with adequate buffer and dynamic range to work just fine.
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Re: Frequency Response Analyzer with Bode Plots

Postby srnec » Tue May 17, 2016 7:35 am

Hello,
with version 0.5.3b and the 5244B on double-head USB cable i got following error:
Error: Unable to initialize device with serial number CZ108/032
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Re: Frequency Response Analyzer with Bode Plots

Postby hexamer » Tue May 17, 2016 12:23 pm

srnec wrote:Hello,
with version 0.5.3b and the 5244B on double-head USB cable i got following error:
Error: Unable to initialize device with serial number CZ108/032


Hello and thank your for taking the time to report. I'm not certain, but I assume this is because the driver reports that the power supply is not connected. As noted earlier in this thread, the application does not currently handle that mode. Does it work if you plug in the AC adapter?
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Re: Frequency Response Analyzer with Bode Plots

Postby srnec » Fri May 20, 2016 8:54 am

hexamer wrote:Does it work if you plug in the AC adapter?


Hello, yes with aux 5V is it working, but 5244B is supplied without 5V adapter because USB power is enough for 2 CH scope. Is it possible to avoid this by modification of FRA?
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