I am trying to devise a way to test the electrical conductivity/resistivity of the atmosphere through rising altitudes. The platform for the experiment is a NASA weather balloon with the allowance of a 1 kg payload. I have started by creating a sort of leaky capacitor design which involves the collection of charge on two parallel plates spaced closely together. The problem is getting a measurable reading. The output signal at this point will be on the scale of femtoamps. This requires the use of an operational amplifier with an inverting configuration. Unfortunately after months of working with op amps of various sensitivities, I still can't get a stable reading. The signal either rails or has no gain at all. I'm afraid my skill level for working with circuitry is what is lacking here. Does anyone have ideas for getting a reading without using an op amp? I admit I'm in over my head here, but I'm not ready to give up!