Keithley 2231A-30-3 Power Supply Measurements

A follow-up video where I have a closer look at the performance of the Keithley 2231A-30-3.
The regulation and accuracy are really quite good, and stability also doesn't seem to be a problem. Which is no surprise - as it turns out, my concerns were unfounded, because the PWM is in fact derived from a proper voltage reference: • Keithley 2231A-30-3 Po...

[@sdgelectronics]

Great follow-up. Given the measured spot measurements of accuracy, I have a feeling that buffer on the PWM output might have the supply fed from a precision voltage source somewhere. Either that or they are using an adjustable regulator and have a grey beard designed low tempco feedback compensation network.

[@kitsune-denshi]

+SDG Electronics Ah, that's the solution to the mystery! Upon closer inspection, it turns out that the buffers are fed from a REF3025. I had completely missed that component until I went looking for it. Thanks a lot for the hint, really good intuition!

[@nlhans1990]

I guess @SDGElectronics is right, the buffer is probably fed from a voltage reference that drives a 2nd or 3rd order R-C low pass filter. A 14-bit of 16-bit DAC costs ~3 euro's each, where a 3rd order R-C filter costs like 20cts in parts. Times 6 becomes quite a considerable saving. Additionally, on a power supply you are very unlikely to change the output more than a few times per second, so a 14-bit DAC with 10us settling time is of no use. That shows in the very slow turn on time though, because 100ms is really really slow.

[@bobfuller]

I really enjoyed the 3 videos. Definitely learned more from your "mistake", so keep making mistakes on all you videos. Lol. Can you share more details of your "poor mans electronic load"? Maybe a quick circuit diagram and the components used.

[@kitsune-denshi]

+Bob Fuller Thank you for your comment - I'll definitely try to keep my learning in the videos! As for the electronic load (if you even want to call it that), I just put a very brief write-up on the web site: kitsune-denshi.net/projects:load It's really embarrassingly simplistic, but it's ok for jobs like this. Feel free to ask any questions and I'll try to answer them.

[@bobfuller]

+kitsune-denshi thank you. BTW I also liked your Panasonic scope video, especially the out-takes. There was no way to make comments on that video, though.

[@bobfuller]

+kitsune-denshi. For a "quick and dirty" report your electronic load write up was actually very informative and helpful. Nicely done. Thank you. I have commercial electronic loads but sometimes I just need a quick and dirty custom solution, so I'm always interested to see different, simple designs.