High Impedance Voltmeter

Discussion in 'The Projects Forum' started by xXxCOZxXx, Jun 9, 2010.

  1. xXxCOZxXx

    Thread Starter New Member

    Oct 3, 2009
    Hi All

    I have been given the task of designing and building a high impedance voltmeter. I have been given a few circuits of voltmeters however i dont really know how one works (in simple terms please) and also how you would know what needs to be in one? I know this may be quite a long question but i really need to know how it works and why certain components would be used to enable me to fully understand and build my own.
    If anyone could help me that would be great.
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    What is the definition of "high impedance" for this project? Do you need an electrometer front end? What is the range of voltages to be measured? What is the desired resolution of the readout, and what kind of readout is needed?

    You have been
    by whom? Is this in conjunction with a school, or as a job function?
  3. k7elp60

    AAC Fanatic!

    Nov 4, 2008
    When a voltmeter is attached to a circuit to measure voltage, it put a slight load on the circuit. The input impedance of the voltmeter determines what the load is in current. I would most modern voltmeters of the DVM (digital volt meter) have an input impedance of 10MΩ. I the scale chosen is 20V, then on the 20V scale the circuit sees a 10MΩ load. In most cases this does not affect the circuit under test.
    There is a DVM IC available that may help you, it is ICL7107 the PDF file is attacted.