Products > Test Equipment
Accurate Low Amp Current Probe Advice
MarkL:
After being distracted by the AM503B internal serial port hacking, I got around to checking the stability of my second AM503B. This is the one with the additional 100uF capacitor discussed in Reply #214.
It's slightly better than the first one, having a drift of about 0.4mA over 30 minutes as compared to 0.5mA. Short-term variability and noise look about the same.
This is close enough for me to not start modifying the first one by adding the additional capacitor. This capacitor is out for a reason, and without a schematic to understand its exact role there may unknown side effects. And not to mention my long-standing mantra: If it ain't broke...
I've ordered a pair of the Amphenol connectors to build the cal adapters. I'll post calibration results for both units when available.
KungFuJosh:
--- Quote from: MarkL on November 16, 2024, 09:57:04 pm ---This is close enough for me to not start modifying the first one by adding the additional capacitor. This capacitor is out for a reason, and without a schematic to understand its exact role there may unknown side effects. And not to mention my long-standing mantra: If it ain't broke...
I've ordered a pair of the Amphenol connectors to build the cal adapters. I'll post calibration results for both units when available.
--- End quote ---
After everything I've swapped with mine, I would say the most value caps to replace are the 1000 and 2200uF caps. Maybe the BP 1uF also. Nothing else made much of a difference, though thankfully I have no regrets. 😉 My power supply caps had already been replaced with very high quality low ESR caps, so I didn't change those.
Where did you find the connectors? I found a decent deal on eBay for the 165-9-1000 variant.
Thanks,
Josh
MarkL:
--- Quote from: KungFuJosh on November 16, 2024, 10:26:36 pm ---...
Where did you find the connectors? I found a decent deal on eBay for the 165-9-1000 variant.
Thanks,
Josh
--- End quote ---
On ebay. They look like the ones you bought, maybe even from the same seller, but I don't have them in hand yet. I offered $24 for a pair. My backup plan was to find the right size male pins and (carefully) push the few connections that were needed into the AM503B connector for the calibration. That would be ok given how often I'm likely to do this procedure.
Unfortunately I should have ordered 3 since I discovered the AM503 has a different pinout for its cal adapter. Maybe I can make one of them do double duty.
I also have an A6302 with a broken transformer that I was thinking about scrapping for the connector, but I haven't given up looking for a new transformer for it yet.
I did replace my TM503 caps some time ago, and that took care of a significant amount of line noise on an FG504 and a AM502. It also helped both the AM503's, but made little difference on the AM503B's. I think my AM503B's may be in healthy condition already. When I get a chance I will poke at those caps with the LCR meter and compare to your measurements.
KungFuJosh:
--- Quote from: MarkL on November 16, 2024, 11:21:22 pm ---On ebay. They look like the ones you bought, maybe even from the same seller, but I don't have them in hand yet. I offered $24 for a pair.
--- End quote ---
Sounds the same as mine, I got 4 for $48 from here: https://www.ebay.com/itm/313033033242
I bought this cable and cut off the SMA end for the voltage adapter: https://www.amazon.com/dp/B0BBYTZM23
I posted the details previously, but in case you didn't see it, coding resistor is 1.13k for voltage adapter, and 15k for the pass through adapter.
Thanks,
Josh
MarkL:
I took a look at the caps you found needed replacing in your unit, namely the 2200uF, 1000uF, and 1uF BP. In my older unit they are clearly showing their age, but in the "new" unit they are still doing well. All are still in spec using the EOL information from each series' datasheet. Since both units are working fine, I'm going to leave the caps alone.
I'm still waiting for connectors for the calibration, and will post the results when done. (And that was the same seller for the connectors.)
Edit: Oops, fixed cut & paste error in spreadsheet image.
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