Hi,
What do you mean by connection is not a problem?
From the circuitry Where is the return bath for the capacitor, is it going to be a virtual ground on the inverting input?

Yes, the return path is the virtual ground, which is maintained within a few mV of 0V by the op amp feedback.
I assume that's okay but my question was: is a connection to (virtual) ground a problem for the test you want to do?

 

Yes, the return path is the virtual ground, which is maintained within a few mV of 0V by the op amp feedback.
So is a connection to (virtual) ground a problem for the test you want to do?

I am not sure if that would be a problem.
What are the straight constrains/limitations with this configuration?

I would need to maintain a voltage across the capacitor at 10Vpeak 1kHz and the capacitance value will be changed during the test depending on the medium used as a dielectric, but it will change probably from 1nF - 100nF

 

What are the straight constrains/limitations with this configuration?

The main limitation is the op amp characteristics, but most general-purpose op amps should work fine for this (although the LM324/358 are not recommended because of their large crossover distortion on the output).

the capacitance value will be changed during the test depending on the medium used as a dielectric, but it will change probably from 1nF - 100nF

100nF would give 100 times the output voltage (over 60V pk with the 10kΩ feedback) which the op amp couldn't do.
So you would need to either reduce the input voltage, or switch in a lower value of feedback resistor (whichever is easier) to keep the output within the op amps voltage range, depending upon the capacitor value.

The op amps maximum output voltage depends upon the supply voltages and whether the op amp is a rail-rail type.
(A standard op amp peak output will typically go to within about 2V of the supply voltages, while a rail-rail type will go to very near the supply voltages).

 

hi t.h.
Have you decided on a possible circuit option.?
E

 

The main limitation is the op amp characteristics, but most general-purpose op amps should work fine for this (although the LM324/358 are not recommended because of their large crossover distortion on the output).
100nF would give 100 times the output voltage (over 60V pk with the 10kΩ feedback) which the op amp couldn't do.
So you would need to either reduce the input voltage, or switch in a lower value of feedback resistor (whichever is easier) to keep the output within the op amps voltage range, depending upon the capacitor value.

The op amps maximum output voltage depends upon the supply voltages and whether the op amp is a rail-rail type.
(A standard op amp peak output will typically go to within about 2V of the supply voltages, while a rail-rail type will go to very near the supply voltages).

Thank you, I will have a look more in details how to implement this

 

hi t.h.
Have you decided on a possible circuit option.?
E

Hi eric,

I decided to try both way and test them and see how it goes

 

Hi eric,

I decided to try both way and test them and see how it goes

If your AC or DC current doesn't exceed 5A, 20A, or 30A then you can easily use ACS7xx Bidirectional Current Sensor with Arduino Nano and the code is very simple.

 

If your AC or DC current doesn't exceed 5A, 20A, or 30A then you can easily use ACS7xx Bidirectional Current Sensor with Arduino Nano and the code is very simple.

Hi jayanthd,

I have used quite a lot of Allegro current sensors and they are not accurate for really low current measurements.
As I have mentioned on top the RMS current can be as low as 60uA