Current Sensing using Opamp

[nishal]

current sensing with opamp

I need a schematic which senses AC Current (from IGBT) using a simple OPAMP and with gain adjustable. The output will be connected to PIC adc for displaying the load connected in the UPS.

Thanks in advance.

-Nishal

 

[heychel]

Do you also need a galvanic insulation between the measured current and the pic?

 

[nishal]

Thanks Heychel for your immediate reply

insulation is not necessary since current sensing output will be only in millivolts.

- Nishal

 

[kepi19]

I think it can help you.

You should put a resistor (a smaller one, like 1 ohm) in serie whith the current source. Then, you should use a operational amplifier to measure de voltaje drop across the resistor.

This circuit has a gain of 1 (1 mA on R results in 1 mV on Vo).



If you want another gain, here is the formula.

Considerate that you'll have a sine signal, that cross between +v and -v.

You should use a rectifier bridge before R to have a all positive signal.

After the operational amplifier, you can use a filter to have a CC level, or take equally spaced samples on your PIC (>> 100Hz) to reproduce the signal value.

I hope that it helps you.

Excuse my English.

 

[nishal]

Thanks Kepi for your detailed info

-Nishal