Products > Test Equipment
An investigation about ripple current of Kunkin KP184
electr_peter:
--- Quote from: burkm on February 21, 2022, 08:56:06 pm ---Any idea, what can be done about this ???
I got this same problem in combination KP184 and BK 9174 power supply. The BK 9174 was quite expensive and it goes into overvoltage or overcurrent protection below the range extremes, when this happens...
--- End quote ---
Potential solution requires to know more details. Under what conditions instability occurs? What is the connection setup with leads? Which load mode do you use? Which instrument is turned on first? Can you increase load gradually?
burkm:
--- Quote from: PaWill68 on July 20, 2021, 01:38:12 pm ---Friends, there is good news. KUNKIN has released a firmware update:
1) The voltage is read by reading one register, and the voltage value is obtained after smoothing and filtering, so there will be no sawtooth shape. The voltage acquisition rate before smoothing and filtering is 470SPS, and the voltage value after smoothing and filtering, the refresh rate is relatively low, it is 10SPS.
2) Instructions to set the battery discharge mode, half-current discharge is enabled and can be saved
--- End quote ---
I got a new KP184 a few days ago and it seemed to work just fine (original firmware version was probably the predecessor "2020 something").
After the firmware update (see above) the KP184 was functioning "OK" for several hours, but now, in the midst of a continous 6VDC / 1A load measurement the voltage display (plus the corresponding wattage display) stopped working, just showing now "all zeros", no matter what signal it was currently fed.
I haven't had any success in finding the cause even after intense searching, although I tried a different (proven) lab power supply from BK Precision I got in my "lab" instead of the Rigol DP832A, different input voltages and amperage profiles, switching voltage sensing from "remote" to "local", a reset to factory default parameters, disconnecting it from the mains, turning it off and on again etc. etc. etc...
Measurement gear connected directly to the output of the power supply are prove of a functional power supply by either unit. Voltages etc. are continously monitored by two Rigol Lab DMMs (6 1/2 and 5 1/2 digits resolution) Everything I could think of to remedy the problem I already tried. I inspected all the PCBs inside the unit without any success and found no hint about any visible cause for the failure. Main board version is "5 (202012)" including the daughter board, display board version is "3". The included test certificate is dated October 20th 2021. Could be a firmware "thing", because your firmware update notes for the new firmware seem to point suspiciously into that direction (=>voltage handling) ?
I don't know, what is going to happen, if I am trying to reinstall the firmware -again- , which is on the KP184 already. Reason: I don't want to be left with a non-functional unit in an incomplete firmware update state, if it's not possible to reinstall the firmware version over the existing one, because i might return the disfunct device. This seems to be my last resort before returning it to the seller...
Otherwise if this is not possible, I would try to reinstall the previous firmware version. Do You have it also ?
If nothing helps, I will contact the seller, being on the verge of returning the KP184, if the problem can't be resolved on my side...
Ps.: Is that new firmware an official release of the manufacturer (Kunkin) or is it "homebrew" ?
If it is "offical" could you check, if an update for that firmware is avilable, may be a "bug fix" ??
burkm:
I tried to message directly the user "PaWill68" several days ago, but he did not respond, neither to the post here nor to my PM message adressing him directly.
Several days have passed since my post dated February 23rd 2022 but no answer from PaWill68 yet... Well...
burkm:
The seller of the KP184 sent me a (free) return label in the meantime.
After a recent clean-up of my (messy :)) "hobby"-room (inluding moving around and lifting up the KP184 several times) and just before returning my non-functional unit I turned it on "a last time" just to casually check, that everything was as before.
To my surprise the voltage and wattage display seemed to be showing real voltages and wattages again, not just "zeros" as before. Now I'm thinking of a "cold" solder joint, loose connection or something similar etc., which might have caused those problems.
Some have already posted about manufacturing problems in this respect...
I contacted the seller - again - and he gave the permission to open up the sealed unit's case to look after those problems and eventually have them fixed right away. If I will find anything I will report back...
dirtcooker:
--- Quote from: atarian on February 21, 2022, 08:47:40 am ---In greater details:
DC coupling, 200mV and 400ns /div
--- End quote ---
I have 2 kp184 units, and can confirm noise coming from it at around 500khz. I purchased this one Oct 2020, and made the following mods: removed C58 (10 nf on v4 motherboard) to reduce instability at 1A current sinking, removed paint under cover screws, applied kapton to rear screws (which are connected to + output), replaced binding posts. old ones > 4mm inside dimension reducing contact with banana plug.
A 10nf cap across the binding posts reduces the noise somewhat. Note that I live in the city, and there is a lot of RF noise from nearby radio stations, unfortunately, which you can see on my scope.
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