I would like to add a LED current meter to the output of a squarewave ozcillator.
I found loads of designs to display voltage, done with a row of Opamps or with the LM3915.
But how do i adopt this to meassure current?
About 8 LEDs should display 1mA to 15mA.
Supply voltage is 18V.
The output ozcillates between +/- 13V.
My thinking sor far:
I could put a resistor of upto 10 Ohm in line, which would then have upto 150mV.
But how can I feed this to an opAmp? Because the voltage of the two connections of the resistor have no relation to any other point of the circuit, I don't see how to create a reference voltage for the opAmps.
I hope it makes sense what i'm saying.
Maybe my thinking is all wrong and there exist completely different solutions...
Anybody can come up with one please?
Thanks a lot!