Measuring Very Low Currents - Picoammeter Adapter (Louder audio)
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- Опубликовано: 2 окт 2024
- ** Re-uploaded with louder audio **
I built the picoammeter adapter designed by "Gyro" on the EEVBlog forum.
The video describes how it works, it's construction, and a basic test.
It seems to work quite well, though I'm having problems with noise at the output levels of just a few millivolts (which is probably caused by the way I've done things).
Links to the EEVBlog forum threads:-
www.eevblog.co...
www.eevblog.co...
Nice build and demo - two quick thoughts. First one is simple - set your voltmeter to average 10 or more readings - you should be able to get another "reliable" digit that way. Second is more complicated, but typical for electrometer grade instruments - use a triax cable where you set the inner shield to same potential as the inner conductor. Your circuit will need to be quite a bit more complicated, but that is what it typically takes. This is by no means criticizing your work - just thoughts for how to take it further.
Thanks!
Yes, I normally do set the meter to 100PLC to get more stable readings when I'm trying to get the most accuracy - I don't know why I didn't do that here...
As for Triax, I want to see where I can get to without it, before climbing down into that expensive rabbit hole!
As you suggest, guarding, shielding and grounding all need looking at. But for me, this was a nice first cut, and there's lots of scope for further experimentation and development of an improved version.
@@bertoid Does Triax need to be expensive? I get the impression that the name brand triax cables are expensive but, I think, there are some lower-priced alternatives that might be sufficient.
@@thedanyesful Doing some Googling, I see that triax is a brand name (for other stuff) - but triax is short for triaxial, which is a descriptive term. If you know of cheaper alternatives, I'd like to know about them, but I'm fairly sure this stuff (and the connectors for it) is just plain expensive!
@@bertoid Yeah I didn't mean to imply that triax was a brand. I was referring to 'brand name' in the sense of a recognizable brand like Fluke or Keithley. I see some no-name triax cables on eBay starting at $20. They call the triax connector '3 lug TRB' if that helps you search it.
At those sorts of amplifications you're probably reading the noise floor of the opamp and thermal noise of the resistor. Not to mention turning absolutely every other electrical appliance off or just going outside with it might also improve noise.
Good points. Playing with such sensitive circuitry is pretty new to me, so I expect to learn a lot about noise and shielding...
Thank you for the re-upload. Grtz
THINK YOU
DIY Faraday cookie tin?
Something like that. I going to play with gutting out a small microwave or toaster oven, and try putting everything in there...