Measure direction of subpicoamp current

AI Thread Summary
Measuring the direction of subpicoamp currents is feasible, particularly in the femtoampere range, using specialized commercial instruments that can detect currents below a picoampere. The measurement method often involves translating current into voltage through a high impedance, though this approach has limitations due to factors like Johnson noise. Instruments such as those from Keithley provide practical solutions for these measurements. Additionally, resources from Analog Devices and Texas Instruments offer further insights into best practices and device specifications. Accurate measurement depends on the impedance used and the specific conditions of the setup.
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Is it possible to measure the direction of a current at current magnitudes this small? Or only its magnitude?
 
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Measure using what method.
It is possible to measure the direction of currents to ground in the femtoampere range.
 
There are many commerical instruments that can go well below a pA
See e.g.
http://www.keithley.com/products/dcac/sensitive/lowcurrent/?mn=6485

This is from the point of view of the user no different than using a multimeter.

Note that how well you can do this will depend on the impedance, it is possible to measure very small currents if you somehow can "translate" your current into a voltage via a (large) impedance (but there are limits to how this can be done, e.g. the Johnson noise of the impedance).
 

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