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Looking for ideas to DIY uA Meter (shunt amplifier)
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Kleinstein:
With a reasonable amplifier one could about resolve some 1 µV at the shunt. So if a 3.5 digit resolution is needed one would need some 2 mV as the minimum shunt voltage - a little more would make it easier (less critical amplifier)  and more accurate.

If the shunt is part of a power supply, the usual way is to have the voltage regulation to already compensate the drop at the shunt. So the shunt would than be more like chosen for a 100-500 mV  drop depending on the current. In addition the shunt can be part of the voltage regulation circuit.
001:

--- Quote from: Kleinstein on December 14, 2018, 12:16:12 pm ---
If the shunt is part of a power supply, the usual way is to have the voltage regulation to already compensate the drop at the shunt. So the shunt would than be more like chosen for a 100-500 mV  drop depending on the current. In addition the shunt can be part of the voltage regulation circuit.

--- End quote ---

Yes
It is simple way
But I`m gonna build not a panel meter


--- Quote from: Kleinstein on December 14, 2018, 12:16:12 pm ---With a reasonable amplifier one could about resolve some 1 µV at the shunt. So if a 3.5 digit resolution is needed one would need some 2 mV as the minimum shunt voltage - a little more would make it easier (less critical amplifier)  and more accurate. 

--- End quote ---

What do You mean?
It will be Ok to clone uCurrent?
Why Dave discontinued it?
David Hess:
I do not understand the problem.  Either use a current shunt and amplifier or use a transimpedance amplifier to provide zero burden voltage.  Note that current feedback amplifiers make pretty good transimpedance amplifiers because of greater stability which can be problem with capacitive loads.  None of this is particularly difficult.

If using a current shunt, then a chopper stabilized amplifier will give the best performance however current shunts tend to have a lot of thermocouple junctions so a standard precision amplifier may be just as good.

Kleinstein:
I would not recommend a current feedback amplifier for a TIA. They are nice and fast, but the DC performance usually kind of sucks - high bias current at the negative input and usually poor drift.  To make use of the high speed the feedback resistor is kind of fixed to a relatively low value.

There are ways around the problem with capacitive input at an TIA:  especially an RL parallel combination at the input.

Good shunts are made with a low thermal EMF material (e.g. Manganin)  and usually there are only 2 junctions at the shunt that matter. For low voltage one still has to keep the thermal layout in mind. Todays chopper stabilized OPs are not that expensive anymore - so not real problem using one of these. With a current in the mA range input bias, which can be in the 100pA range is usually not problem anymore.

There is nothing special with Daves µC current. So you are free to build your own version of shunts + amplifier - maybe just not call it µCurrent though.
001:

--- Quote from: Kleinstein on December 14, 2018, 05:09:02 pm --- Todays chopper stabilized OPs are not that expensive anymore - so not real problem using one of these

--- End quote ---

Thanx
What OP will be ok?
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