Electronics > Metrology
V-I Curve tracer / Component tester
timeandfrequency:
Hello Veketti,
So it was just an artefact that came from the setting of the oscilloscope :-/O
I would suggest you always select DC coupling.
Because what I saw (in AC mode) was a constant negative current (while the voltage was varying) : only constant current diodes show up such a particular behaviour.
--- Quote from: Veketti on February 11, 2025, 05:55:53 pm ---No trimpots on the pcb to adjust the 4V compensation. However I noticed under microscope that the legs of the 16 pin IC on the bottom right side of the presumably MCU were badly soldered, so I resoldered them and tested it and the 4V looks pretty darn good to me now.
--- End quote ---
Wow ! Kudos, you just fixed it :-+, because the slanted trace meant the TE was defective on delivery :palm:.
Veketti:
If I may continue little still, now that I've been playing around with it more. It seems that with the highest frequency 2kHz there is line separation even when the leads are disconnected. Does it mean that there are internal capacitance and whether it's normal to behave like this (see attached picture)? Would this be caused by bad design, inferior/bad components or something else?
In which case you'd need this high frequency that lower frequencies wouldn't work?
Too bad that the scope don't support ref when in XY mode. Is it normal for DSO's not supporting Ref in XY mode? Would be awesome on pcb to probe known good component and then press ref to get the waveform on display and then probe all similar components to see whether they match. Well there's the A/B function in curve tracer, but it's bit cumbersome as you run out of hands. ;D
timeandfrequency:
Hello Veketti,
--- Quote from: Veketti on February 12, 2025, 07:12:20 pm ---If I may continue little still, now that I've been playing around with it more. It seems that with the highest frequency 2kHz there is line separation even when the leads are disconnected. Does it mean that there are internal capacitance and whether it's normal to behave like this (see attached picture)? Would this be caused by bad design, inferior/bad components or something else?
In which case you'd need this high frequency that lower frequencies wouldn't work?
--- End quote ---
That's common on V/I trackers: at higher frequencies, the internal stray capacitances separate the trace. This is not to be considered as an issue.
Higher frequencies are mainly used to test capacitors and inductances that display an elliptic trace.
For these parts the possible values span over 9 to 12 orders of magnitude.
So in order to see a nice ellipse (and not a flat one), you need to select an adequate frequency.
--- Quote from: Veketti on February 12, 2025, 07:12:20 pm ---Too bad that the scope don't support ref when in XY mode. Is it normal for DSO's not supporting Ref in XY mode? Would be awesome on pcb to probe known good component and then press ref to get the waveform on display and then probe all similar components to see whether they match. Well there's the A/B function in curve tracer, but it's bit cumbersome as you run out of hands. ;D
--- End quote ---
It probably depends on the scope model, but I guess that the reference trace feature is not that common when using XY mode.
On V/I trackers, the A/B function is dedicated to parts comparison.
If you're short on hands^^, upgrade the provided probe set with some Kleps or miniature crocodile clips.
ME:
why is the scan so poor the result is tiny and unusable?.
Veketti:
--- Quote from: ME on February 18, 2025, 02:26:48 am ---why is the scan so poor the result is tiny and unusable?.
--- End quote ---
You mean bad resolution? Well Siglent SDS800X HD -series don't really shine when it comes to XY mode. Or in other words, should I say that any analog scope beats DSO's in XY mode :popcorn:
This is partly the reason why I resurrected old Tek CRT scope..
edit: Only disadvantage is taking a screenshot is bit more hmm old school. :-DD
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