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sensor interface 4-20 ma

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M

Moof

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How i should make the interface to conect a sensor output (4-20 ma) in a microcontroller ADC??. An operational configured "current to voltage" or just a resistor?
 

Only need one resistor.Sample 250 Ohm.But sensor flow 4ma for zero and flow 20ma for fullscale.
If fullscale ad converter resolution 3FFH(0-1024) FOR 5V


CPU ad converter measurment=(250 ohm x Imeasure)-(250 ohm x 4ma)
=(250 X 20ma)-1v
=5v-1v=3FFH-CCH=333H

For 4-20ma your measurment range 0-333H=0-819D
 

    M

    Moof

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You should use 100R or 250R 0.1% 1/2W resistor in sries in 4-20mA loop,then connect it to a instrumentation amplifier (differential to single ended conversion,common mode rejection) then do some filtering and ADC conversion.you should cancel 50/60Hz noise.
 

    M

    Moof

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here is a good book about instrumentation you may find what you want there
 

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