I want to measure the current at point A. This is a constant current circuit driving a laser. But to connect it with INA219, how can I connect it to my circuit?
Option 1: Do I need a shunt resistor in series and Vin+ and Vin- are connected between resistor?
Option2: Vin+ is connected to supply (12V) and Vin- is at point A.
Option3: Vin+ and Vin- are connected along the path of the current without resistor, just like the connection of multimeter.
Also mine is a constant current circuit of 21mA, so the variations will be less. Is there any way to calibrate the sensor to measure the small variations?
Please spare me if my doubt is very basic. I dont have much experience with analog electronics. I watched many youtube videos, but in each one its is telling differently. Thanks in advance
The opamp diagram in this version is incorrect. The opamp (without feedback) will try to deliver it's max current here, and could destroy the Laser. The diagrams in your other two cross-post were sort-off getting there.
You could use the INA219 to measure that current, but it's resolution (A/D steps) is AFAIK 3mA. An INA239 has a much higher resolution.
Just cut the trace between opamp and Laser, and connect opamp to +IN and LED to -IN.
Don't know why you want to measure that current if you alredy know what it's going to be.
Leo..
@tinu_arduino
You don't need a INA219 to measure current.
If you use this circuit, the voltage across the 281 ohm resistor represents the current
current = voltage/281
