Frequency Response Analyzer with Bode Plots

[hexamer]

Hello Aaron,

do you plan to support (cheap) external function generators e.g. like the FY6800?
Would be nice to extend the frequency range to 60 MHz.

with best regards

Andreas

Hello Andreas,

You may know that I recently added an ability to extend FRA4PicoScope to allow for external signal generators using a modular (DLL) approach. The first example is based on a home brewed DDS I made based on a EME165-R2. I did this mainly to support another project I was pursuing at the time, and partly because external signal generators are a common request. To do it right, it needed to be modular given the many possible signal generators.

Given that I don't have access to other signal generators and have satisfied my immediate needs, I don't have any high priority plans to create other plugins. Longer term, I would like to further prove-out the extension interface. Likely candidates would be to support (1) common interfaces like SCPI or (2) like you mention, instruments readily accessible to hobbyists.

Thanks,

Aaron.

[mransaw]

I would be happy to help here, just would like to know some more details. Are you using the low noise mode (default) or noise reject mode? While you're getting back to me, I'll see if I can deduce what's going on here.

Also, the message "Signal generator plugin not configured." is actually expected - though maybe not so intuitive. What it's trying to tell you is that you tried to connect an external signal generator (i.e. not the one in the PicoScope) and were not successful. To correctly setup an external signal generator you have to supply a DLL and parameters. Correct me if I'm wrong, but I assume you don't really want to setup an external signal generator. The default configuration of the app is to use the PicoScope's internal signal generator, which is what a vast majority of people will want to to (at least initially).

Aaron.

Hi Aaron,

I was using the low noise mode. I just tried the noise reject mode and it seems to work.

I am using the PicoScope's internal signal generator.

Thank you,
Miles

[hexamer]

Hi Aaron,

I was using the low noise mode. I just tried the noise reject mode and it seems to work.

I am using the PicoScope's internal signal generator.

Thank you,
Miles

Hmm, the plot thickens This points to some sort of initialization (or lack thereof) sequence issue.

Are the issues with low noise mode repeatable? Specifically, if you launch the app in low noise mode and try to run a FRA, does the "inf" error happen every time? If so, would you mind posting the results of a session with API tracing turned on? Tools->Settings->Log Verbosity button, turn on PicoScope API Calls. Try to run a FRA, then copy the log and post it here.

[Emgu]

Hello Aaron!

Thank you for this software!
We are using your software for characterization of a contact impedance and are using a reference resistor in series with our contact. So that they form a voltage divider. Channel A is measuring at output of the AWG and channel B is measuring between the DUT and the referece resistor.
I have a question about the operation of the software:
Does the "stimulus amplitude" refer to the voltage of the AWG or to the voltage between the two channels used for measurement? For our interests, ideally the voltage across the load should be kept constant along with the voltage of the AVG.
Kind regards
Emanuel

[develx]

Hello!

I'm evaluating to buy Picoscope 5244D for to analyze the frequency response of my SMPS prototype.
The 5244D model is supported at this moment by FRA4Picoscope?

Thanks in advance
develx

[hexamer]

Hello Aaron!

Thank you for this software!
We are using your software for characterization of a contact impedance and are using a reference resistor in series with our contact. So that they form a voltage divider. Channel A is measuring at output of the AWG and channel B is measuring between the DUT and the referece resistor.
I have a question about the operation of the software:
Does the "stimulus amplitude" refer to the voltage of the AWG or to the voltage between the two channels used for measurement? For our interests, ideally the voltage across the load should be kept constant along with the voltage of the AVG.
Kind regards
Emanuel

Hello Emanuel,

Thank you for your interest in the FRA app!

The "stimulus amplitude" refers to the voltage of the AWG. If you need to keep a constant voltage on the load, you'd need to try "adaptive stimulus" mode or "custom plan" mode, depending on how constant you need it to be.

Adaptive stimulus mode can control the stimulus amplitude to cause the input or output amplitude to track closely to a specified value. But it was designed with SMPS measurements in-mind. Given that, it works by seeking the minimum stimulus amplitude that still achieves the target output response of the input or output channel with the lowest amplitude response (I know ... quite the mouthful!) So, depending on the nature of the voltage divider, you may not be able to control just the voltage on the load. If the voltage divider is such that the voltage across one element is always larger than that across the other, this mode could work for you.

EDIT: One other point here is that in this mode, while seeking the best amplitude, the application can apply more voltage than the final target. I assume since you say your load is a "contact", that we're not concerned about physically damaging it? Perhaps your load's impedance is actually voltage dependent? Something I think often surprises people is that a ceramic capacitor's capacitance is voltage dependent. If you hookup a simple RC filter with a ceramic cap to the FRA app and run in custom plan mode with varying stimulus, you can easily see this effect on the response.

Custom plan mode is a way to define a stimulus amplitude based on frequency ranges. The main limitation here could be that it allows only up to 10 segments to be defined. Depending on how tightly you must control load voltage that might not be enough precision.

If you could give more details on the nature of the reference resistor and DUT, we can figure out a proper solution.

Thanks,

Aaron

[hexamer]

Hello!

I'm evaluating to buy Picoscope 5244D for to analyze the frequency response of my SMPS prototype.
The 5244D model is supported at this moment by FRA4Picoscope?

Thanks in advance
develx

Hello develx,

While I cannot say that I've personally tested the 5244D, I will tell you that I own a PS5444A which I regularly test and they use the same driver family. The 5244D should be an excellent choice for SMPS measurements given its very large dynamic range and sample buffer. If you had any issues, I'm more than happy to help make it work for you.

Thanks,

Aaron.

[mnni]

Hello Aeron

Have you heard anything from Pico tech regarding the possible rounding issue in the scope driver ? when using the sigGen function instead of the awg function

[develx]

Hello to everyone,

I'm preparing the measurement of stability of my SMPS prototype with my 5444D picoscope.
The SMPS prototype is connected to my electronic load.
The chracteristics of my SMPS prototype are:
- input: 220 VAC (connected to the AC main)
- output: 24VDC - 10A (240W)

other informations:
- the 5444D is connected to the laptop with picosocpe 6 and FRA4 via USB cable
- the laptop with picoscope 6 and FRA4 is powered by his internal battery
- the electronic load is power by the AC main (the is the earth connected)
- the alligator of the 5444D picoscope probe is connected to the negative of the SMPS dc output

NOTE: the 5444D picoscope has a screw in the rear panel for the connection grounding.

I have a question about the grounding (connection to the earth):
- It necessary to connect the earth to the screw of the 5444D picoscope?
- It is necessary to power the laptop with AC main power adapter?

I don't want damage my instruments, have you the best practice for the connection with earth?

Best regards
develx

[mnni]

Hello to everyone,

I'm preparing the measurement of stability of my SMPS prototype with my 5444D picoscope.
The SMPS prototype is connected to my electronic load.
The chracteristics of my SMPS prototype are:
- input: 220 VAC (connected to the AC main)
- output: 24VDC - 10A (240W)

other informations:
- the 5444D is connected to the laptop with picosocpe 6 and FRA4 via USB cable
- the laptop with picoscope 6 and FRA4 is powered by his internal battery
- the electronic load is power by the AC main (the is the earth connected)
- the alligator of the 5444D picoscope probe is connected to the negative of the SMPS dc output

NOTE: the 5444D picoscope has a screw in the rear panel for the connection grounding.

I have a question about the grounding (connection to the earth):
- It necessary to connect the earth to the screw of the 5444D picoscope?
- It is necessary to power the laptop with AC main power adapter?

I don't want damage my instruments, have you the best practice for the connection with earth?

Best regards
develx

Hey develx
not always easy with the grounding vs floating avoid ground loop issue.

Is the E-load minus terminal connected to earth ground(PG) internally in the instrument ? it is not always the case with E-loads and sometimes you can do it with a shunt on the instrument back.

you should try only to have one earth ground connection to avoid groundloops -> when you connect the probe gnd alligator clips to the psu reference point this becomes the ground point of the scope and you floating computer !.

perhaps it would be wisely with a simple drawing of the smps and where you plan to connect the scope probes

[ts8051]

Dear Sirs,
I have the osciloscope 3000 series connected with Mac OS operating system. I show in your application library that there is appication for bode plots:
https://bitbucket.org/hexamer/fra4picoscope/wiki/Home
Is it possible to download or how to compile a version of this application compatible with MacOS ? It is very useful application especialy for measuring hifi amplifiers.

Regards
Theologos Sarafidis

[develx]

Hello to everyone,

I'm preparing the measurement of stability of my SMPS prototype with my 5444D picoscope.
The SMPS prototype is connected to my electronic load.
The chracteristics of my SMPS prototype are:
- input: 220 VAC (connected to the AC main)
- output: 24VDC - 10A (240W)

other informations:
- the 5444D is connected to the laptop with picosocpe 6 and FRA4 via USB cable
- the laptop with picoscope 6 and FRA4 is powered by his internal battery
- the electronic load is power by the AC main (the is the earth connected)
- the alligator of the 5444D picoscope probe is connected to the negative of the SMPS dc output

NOTE: the 5444D picoscope has a screw in the rear panel for the connection grounding.

I have a question about the grounding (connection to the earth):
- It necessary to connect the earth to the screw of the 5444D picoscope?
- It is necessary to power the laptop with AC main power adapter?

I don't want damage my instruments, have you the best practice for the connection with earth?

Best regards
develx

Hey develx
not always easy with the grounding vs floating avoid ground loop issue.

Is the E-load minus terminal connected to earth ground(PG) internally in the instrument ? it is not always the case with E-loads and sometimes you can do it with a shunt on the instrument back.

you should try only to have one earth ground connection to avoid groundloops -> when you connect the probe gnd alligator clips to the psu reference point this becomes the ground point of the scope and you floating computer !.

perhaps it would be wisely with a simple drawing of the smps and where you plan to connect the scope probes

I have read a lot about how to connect the instruments for this type of measurements.
At the end of my study, the site was ok and I made the memasurment.
Attached to this thread, there is a picture of FRA4Picoscope with my first measurement.

Thanks for the support!

[ts8051]

Hello,
I have a Mac. How can I compile this application? Is there a ready to run version for MacOS?

[hexamer]

Hello,
I have a Mac. How can I compile this application? Is there a ready to run version for MacOS?

Theologos,

Unfortunately not a lot has changed since this post: viewtopic.php?p=143515#p143515

Are you still able to use a VM approach?

The most likely path to getting something working would be to try to port the API version and make a new MAC-OS specific UI, but even this will likely be a very significant effort.

Thanks,

Aaron

[Nicosten]

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.