Hello guys

I have designed a circuit inspired by uCurrent gold meter to measure DC current with range of -500uA to 500uA.
The circuit does measure current decently but only in low-side configurations.
I was wondering if there's a simple tweak it to allow floating current measurements, as I need to measure current in series.

 

Use something like a INA181, which can measure low-side, high-side up to 26V and anything in between.
INA187 will handle high-side up to 40V.

 

Do you need to measure both high-side and low-side, or only high-side?
For only high-side, there are circuits and ICs designed specifically for that purpose (example circuit below using a RR op amp):

 

Do you need to measure both high-side and low-side, or only high-side?
For only high-side, there are circuits and ICs designed specifically for that purpose.

I am actually looking for both and bidirectional as well..
I take that my built circuit is not gonna be of any help for this purpose..

 

So what will you do with the current reading from the micro?
What's the end purpose of this circuit?

 

So what will you do with the current reading from the micro?
What's the end purpose of this circuit?

For example I want to measure the base current of a transistor or the charge current of a capacitor.

 

For example I want to measure the base current of a transistor or the charge current of a capacitor.

Then how about just using a sensitive multimeter, which can measure voltage on a floating resistance, and give you a digital readout, which you can use to calculate the current from Ohm's law.
For example, I've seen 4 1/2 digit multimeters on Amazon that can measure voltage on a 200mV full-scale with 0.01mV resolution.

 

For example I want to measure the base current of a transistor or the charge current of a capacitor.

In general, measuring current like that is rarely done with a current probe, because of the necessity of breaking the circuit to insert the probe. When there is a capacitor charging, more often than not it is charging through a resistor, and it is easiest to measure the voltage across that resistor without breaking the circuit and calculate the current via Ohm's law.
Similarly, the base current of a transistor is generally provided by some other part of the circuit via a resistor. The current can be determined, more often that not, just by finding the appropriate resistance and measuring the voltage across it.

 

If you want a fully floating and isolated device, power it from an isolated POL module or batteries, and utilize an isolated I2C transceiver such as the ISO1640 from TI. There are other vendors.

 

Someone proposed the following circuit;
Circuit
But I am not sure if it allows low and high-side/floating measurements.

 

Someone proposed the following circuit;
Circuit
But I am not sure if it allows low and high-side/floating measurements.

View attachment 361547

No. It only allows measurements where one side is at half supply, so No on all three counts.