I have been finding a way to measure AC microamps with an arduino as I dont want to buy a couple hundred dollar oscilliscope. The frequency is about 1.5 - 3hz. I need to measure about 5uA - 20uA
So far with the help of someone else I got this Breadboard V3 - Album on Imgur. The current that i am measuring goes in to the top. The first resistor is 1M and the other 2 are both 1k. The two 1k ones are setup to be voltage dividers.
These are the instructions he gave me:
-Measure voltage divider input
-Request a measurement of the 1Meg input, but don't use it.
-wait at least 7 * RC = 7 * 1Meg * 10pF = 70us, so let's call it an even 100us
-Actually measure the 1Meg input.
-Repeat (no other delays necessary)
use 2 ADC inputs to measure the voltage on the voltage divider directly and the 1Meg resistor, and subtract the two measurements. This give the voltage drop across the resistor directly. I like this better, and I'll go with that for the rest of the comment.
Please learn to draw circuit diagrams and post one for your circuit.
I don't see how a 1M resistor together with 1k resistors will allow to measure µA. But you can try and come back to report whether you found it working or not.
I'd look for a serious µA instrumentation amplifier circuit diagram, usable with a DMM or ADC.
I would suggest you spend a bit of time and researching what an oscilloscope will measure. All the ones I have display voltage over time. I have special probes that will measure current but they are very expensive. I would suggest you spend about $50 on ebay and purchase something that will do the job. You can get some very nice desktop units for well under 100 dollars. Read the specifications they may surprise you. To do the job with the arduino you need to design a stable and accurate AC-DC converter and then calibrate it. As a rule of thumb every digit you move to the right of the decimal point squares the complexity of the problem. To calibrate you will need something that will be accurate to 10 times what you are calibrating. IE, 1 volt requires 0.1 volt measurement for calabration.
Good Luck & Have Fun!
Gil
