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Current measurement from 0.1uA to 1A
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Kleinstein:
The logarithmic curve would not be that bad. A problem is that the diode voltage is also temperature dependent. With nonlinear self heating this can get quite tricky is good accuracy is required.

The two or 3 range version is probably the better way.
Kalvin:

--- Quote from: Kleinstein on December 05, 2018, 09:14:50 pm ---The logarithmic curve would not be that bad. A problem is that the diode voltage is also temperature dependent. With nonlinear self heating this can get quite tricky is good accuracy is required.

The two or 3 range version is probably the better way.

--- End quote ---

EDN has a Design Idea for logarithmic current measurement circuit using carefully selected diodes:
https://www.edn.com/design/test-and-measurement/4443319/Multi-decade-current-monitor-the-epitome-of-simplicity

I have no idea how well this will work in real life with real components and/or how hard it would be to find a suitable diode pair. But very interesting idea anyway.
sandy.holmarc:

How quickly do you need to be able to measure the current? Can you tell us something about the application as it would help us understand your requirements better?
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Hi splin,
Thank you very much for the reply.I would like to develop a VI measurement circuit for the solar cell experiment.Measurement time under 3 minute is fine .I need accuracy of 10nA only in uA range measurement ,uA accuracy in the mA range measurement  and mA range accuracy in the A range measurement .
Marco:
Given how often this topic come up, I think Dave should do an auto-ranging multi-output uCurrent.

Have 3 shunts in parallel, with the lower value shunts gated by a bidirectional switch (back to back MOSFETs). When the absolute voltage across the previous shunt goes over a threshold, start smoothly switching in the next shunt.
Habropoda:
It seems like the CurrentRanger could handle this:
https://lowpowerlab.com/guide/currentranger/
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