Picoammeter Design

[exe]

I decided to do my own standoff from filament bowden tube because it's cheap and abundant. Guess what, the tube arrived from amazon has different inner diameter (2mm vs expected 1.9mm that I had on another tube), and was visibly contaminated. Well, at least it cost less than 7euro.


Cutting ptfe to have  straight edged proved to be difficuilt, so I made a fixture to cut the tube.

Now onto pcb. It has arrived. It looks perfect. I removed soldermask and silkscreen as advised. But I also realised that, since I use standoffs, I didn't have to do it. Anyway, it's nice, but soldering without solder mask and silkscreen is more difficult. On a flip side, it does give a vibe of a self-etched pcb. You know, ferric chloride, brown stains everywhere, and that horrible taste (don't taste it).


I tried to print enclosure with conductive filament. It prints nice, though warped a little bit. Conductivity is within spec. Not perfect, so not sure if this provides enough shielding. May be not. The downside is, it contaminates nozzle. After printing with it takes a lot of plastic to purge it. So, I wouldn't print low-leakage parts from the same nozzle.


Now I'm slowly assembly everything together.

PS is it ok that I post in this thread, or shall I start a new one? I'm trying to post here info that might be interesting to other builders.

[BD1QMP]

IVC102 can finish integrating and cap reset.

Has anyone designed an integrating ammeter? I'd like to make one, but not sure how to properly reset the capacitor.

I want to try to short opamp pins to ground (slightly below that compensate for voltage drop of ESD diodes) to reset the capacitor, but I don't know if it's going to disturb the load. There are very few sources on the internet discussing this topic. They say that the load needs to be disconnected, but this would increase complexity and potentially increase leakage.