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| Device for nA Measurements ? |
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| Nicole01:
Hello Everyone, i would like to know how you make Measurements in the nA Range ? Which Devices can you recommend here ? You can't do that with a normal Multimeter. Even with most Benchtop Multimeters it is not possible. What Experiences have you here ? Many Thanks Nicole |
| bdunham7:
There are many variations, but I use one of these: |
| Nicole01:
Thanks for your Help and the Info. I'm looking for a newer Device. It would be good if it was already Digital :-+ |
| bdunham7:
Well, as I said there are many variations. At the other extreme from my very old model, there are: https://www.tek.com/en/products/keithley/low-level-sensitive-and-specialty-instruments/series-6400-picoammeters It depends on what your specific requirements and budget are. The active inputs on typical picoammeters result in a low voltage drop (burden voltage) across them, only a few mV in the case of my ancient 414A. If that doesn't matter and you have a higher-voltage high-impedance source you want to measure, a 10M input voltmeter actually works with 1V = 100nA. Also, there are some cheap converter units like the uCurrent from EEVBlog's Dave Jones and the Current Ranger, a sort of knock off. I don't know much about those two, but they've been discussed here at length and you can search for them. |
| Performa01:
Most DMMs with 10 Mohms input impedance can be used for this in principle. Just use the voltage range, e.g. 200 mV instead of the current ranges. This becomes a 20 nA range and you can measure down to 10 pA with a 20000 count meter. Some (especially true bench) meters have an unexpected high input current up to 1 nA. You can detect this by measuring the open circuit voltage with 10 Mohm input impedance; thus the meters own input current. If this is anywhere above 50 pA (= 0.5 mV), then the meter isn't usable for this purpose. Of course, the "correct" way to do this is using an electrometer; this allows you to measure down to the femtoamperes... |
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