kelvin sensing

Discussion in 'General Electronics Chat' started by jdelaney, Mar 31, 2013.

  1. jdelaney

    Thread Starter New Member

    Aug 2, 2012
    3
    0
    could someone please post a pic of how to implement a kelvin connection to measure battery voltage directly at a 12v lead acid battery and connect that to a pic18f4523 controllers a/d?
    I've attached my charge section and bvolts is from my battery but the voltage drop while charging is causing me to not accurately sense the real battery voltage.

    should the a/d vref+ and vref- be connected at the battery terminals
    via a 5v regulator?


    I would really appreciate any help.

    Thanks
    Jamie
    [​IMG]
     
  2. crutschow

    Expert

    Mar 14, 2008
    12,986
    3,224
    For a Kelvin connection you need a differential type input. You connect the two differential leads to the battery terminals. The measurement then does not see any voltage drop due to cable resistance Since I believe the PIC does not have a differential input, then you need to add a Instrumentation (differential) Amp buffer, such as one of these or these, between the battery and the PIC input.
     
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