0-4mA to 0-3.3V converter

Discussion in 'General Electronics Chat' started by schnnegi, Oct 8, 2008.

  1. schnnegi

    Thread Starter New Member

    Sep 24, 2008
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    0
    Hi can anyone help me on this circuit of converting 0-20 mA standard into 0 to 3.3 volt standard.(using opamp or passive method)This signal is being applied to ADC channel of PIC18LF4620 which is driven by 3.3V.
    There should be no drain while applying this I-V converted signal to ADC input.

    When I am applying this (direct connecting preset pot across current i/p whose output is 3.3V) signal to ADC channel voltage is droped to 1.28V so ADC output is 99 instead of 255.
    When I am using Opamp circuit with LM358 the problem faced is
    :---------------I am converting -5V-0- +5V signal into -3.3-0- +3.3V for applying this to power supply for LM358.
    I used 2 OpAmps in inverting mode.the output is saturated.but when i am applying 3.3 V directly i am getting output.
    I checked this using proteus software.But I have -5 -0-+5V source from which i have to convert this into -3.3 -0- +3.3V signal using 1N4148diode and 3.3Vzeners.
    Can any tell me how I can stop this drain of voltage means i am unable to get this voltage range 0-3.3V corresponding to 0-20mA using -3.3-0-+3.3V supply made from 5-0-+5 volt
     
    Last edited: Oct 8, 2008
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