resistance test

Discussion in 'The Projects Forum' started by chuackl, Sep 26, 2013.

  1. chuackl

    Thread Starter New Member

    Sep 26, 2013
    Hi i am trying to construct a circuit that can judge whether the resistance R in a range of 5k<R<6k. If R is not in this range, it will show fail other wise pass. A LED can be connect in series with R6 as an indicatior. Theoretically, it should be working but i not sure when it come to practical. Any advise or modification needed on the circuit for it to be working?
  2. wayneh


    Sep 9, 2010
    You need a window comparator circuit. Then insert your resistor under test into a voltage divider and look at the voltage across it, compare it to your window voltages. You can OR the outputs so that failing on either end indicates fail.

    The common LM339 or LM393 comparators would be the typical choice.

    Another approach would use the LM3914. This IC contains a series of window comparators and could show you not just pass/fail but where in the range the resistor falls.
    chuackl likes this.