How to use DS1052E to measure quality of step-up/step-down converter

[extasic]

Hi,

I just got step-up/step-down converter board (IC + some parts) I ordered from an asian supplier. I don't have much information about it, only some basic specs:

- fixed 3V3 output voltage
- input range: 1V8 - 5V
- max 500mA output current

My goal is to use it to convert the power of a li-on battery to the 3V3 required by one of my circuits. As I own a Rigol DS1052E and a programmable DC power supply, I wanted to test the "quality" (linearity of output, occurrences of peaks or dips) of the module. I want this mostly for fun and to train using my scope, not for a high-quality blog review 

So this is how my approach I came of with looks like: I wanted to output some voltage curves between the specified input range to the module, and add a 60k resistor as load between GND and the output pin of the converter. I would then attach the two channels of the Rigol to GND and the input and output voltage. Any issues with this test setup?

My main problem is now how I should setup the Rigol measurement. I have played around with repetitive patterns from a function generator (sine/square waves etc.), but I have no idea how I should

- setup the trigger (there hopefully is no "edge" or "pulse" within the constant 3V3 output)
- do a long-time measurement (maybe around 30s, do I need a computer attached to the scope for this?)

I already configured the scope to use the "Long Mem" memory depth, but all captures are only fractions of a second when I stop them.

Do you have any idea how I can realize such a test with this scope?

Thanks in advance and best regards 

[danadak]

I think what you are looking for is in effect a strip chart recorder.

This is a an example used that acts as a data logger, might be useful.


https://hackaday.io/project/810-30w-240w-halogen-led-balcony-solar-lanterns/log/2495-measuring-ui-and-up-charts-of-unknown-solar-panel


Your 60K is not much of a load, just a thought.


Regards, Dana.

[extasic]

thank you for the link!

I'm not quite sure if I understand this part right:

The signal generator (Philips PM5108L, left hand side of image) creates a triangle wave from 0V up at about 40Hz (high enough for fast "frame rate", low enough to not create huge measurement errors). The triangle wave controls the electronic load current. The higher-voltage higher-z output of the signa generator is connected to the ext-trig input of the scope, to trigger reliably.

So does he use the function generator as external trigger to create regular "measurements" and this is the "strip chart recorder" part you propose? Or how should I realize this using the scope?

[danadak]

A strip chart recorder is for relatively low data rate sensor monitoring.

https://www.instrumart.com/products/4675/fuji-electric-phe-strip-chart-recorder

A DSO can act as a recorder at very low sweep / sampling rates, and also can
output those values in MS Office compatible files, like excel, for external plotting.
So DSO could output and collect in a file samples over very long periods of time,
and then you use file to manipulate and plot the data.

The software to use would be LabView or Matlab to do sample capture, display.

Here is a python based approach - http://www.cibomahto.com/2010/04/controlling-a-rigol-oscilloscope-using-linux-and-python/

Regards, Dana.

[extasic]

Here is a python based approach - http://www.cibomahto.com/2010/04/controlling-a-rigol-oscilloscope-using-linux-and-python/

great, thank you very much