Hi,
I want to measure the current from a circuit using Arduino.I made up this schematic and I need your opinion guys.
I'll be using this current sensor and this op amp.
And here are my schematics.I made 2 of the.Which one do you think is better?
Just to be sure:
Thank you,
Bob
The circuit will not work. Look here for some pointers. You cannot use an opamp without adding external resistors to set the gain you require. You cannot use a diode in the signal path like you are doing.
I don't understand scheschematic.
Yes, the burden resistor is good, but far too small I think, This thing does
15mA at full scale, so 150 or 180 ohms seems good to get about 2 -- 2.5V
for 30A in the sensed wire.
You don't normally rectify low voltages with diodes to measure since 0.7V is
lost turning the diode on.
You either read the AC waveform directly by sampling often enough, or use
an op-amp precision rectifier circuit which will have errors of the order of mV.
Connect one side of the CT (current transformer) to a 1:1 voltage divider (say two
4k7 resistors, one each to GND and 5V) so it gets mid-rail voltage of 2.5V. Connect
the burden resistor securely across the CT (if it comes loose very high voltages are
generated). The other end of the CT goes to an analog pin, which you read frequently
and calculate the mean-square value by averaging the square of the
(value - mean value).
If you can find a CT with built-in burden resistor I'd choose that, no risk of it
coming unconnected.
