I need to measure the current flowing through a resistor of 1 Ohms.
Maximum is 500ma.
I need to measure this current with 1 ma resolution and need to provide a calibration out put which should measure 1mv at 1ma.
I wish to avoid low offset op amps like op07 as quad or dual versions are not available here. I prefer LM324.
LM324 is having input offset 2mv. my range is 0 to 500mv at 1 mv steps. So i need to cancel that 2 mv offset using another stage of LM324. I tried in simulator but I cant get stable and linear results in Proteus.
Is this a workable idea? please suggest.
My plan is of LM324
first stage buffer
second stage offset to exactly 0-500ma ( goes to a test pin.(1ma=1mv)
Third stage amplify to 0 to 4.882V for PIC ADC.
Fouth stage a low pass filter .
Thanks. please advice
Maximum is 500ma.
I need to measure this current with 1 ma resolution and need to provide a calibration out put which should measure 1mv at 1ma.
I wish to avoid low offset op amps like op07 as quad or dual versions are not available here. I prefer LM324.
LM324 is having input offset 2mv. my range is 0 to 500mv at 1 mv steps. So i need to cancel that 2 mv offset using another stage of LM324. I tried in simulator but I cant get stable and linear results in Proteus.
Is this a workable idea? please suggest.
My plan is of LM324
first stage buffer
second stage offset to exactly 0-500ma ( goes to a test pin.(1ma=1mv)
Third stage amplify to 0 to 4.882V for PIC ADC.
Fouth stage a low pass filter .
Thanks. please advice
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