Digitial Multiimeter Question

Discussion in 'General Electronics Chat' started by Vindhyachal Takniki, Jan 31, 2015.

  1. Vindhyachal Takniki

    Thread Starter Member

    Nov 3, 2014
    349
    6
    1. I am using digital mutilmeter for measuring voltmeter.
    It has 9V battery for multimeter operation.

    2. My question is when I use digital multimeter for voltmeter purpose, do black probe of multimeter is shorted to its internal 9V battery or both are isolated?
     
  2. ScottWang

    Moderator

    Aug 23, 2012
    4,858
    767
    Why you asking that?
    Unless there is an isolated dc to dc inside, otherwise you can say that they are on the equal voltage level and connected together.
     
  3. ak52

    Member

    Oct 15, 2014
    145
    4
    You can confirm that yourself.If you have another DMM,check continuity between the negative probe and the battery negative terminal.
     
  4. Reloadron

    Active Member

    Jan 15, 2015
    969
    235
    Depends on the DMM. However, in most cases for example if you try to measure the internal battery of the DMM (DMM measuring its own battery) it will not work. A typical 9 volt battery will measure about 6 volts or so. This is because in most cases the meters A/D (-) Input is raised above the (-)Input of the battery lead. The DMM (-) input and the battery common or (-) are not the same reference point.

    Ron
     
  5. crutschow

    Expert

    Mar 14, 2008
    13,056
    3,245
    Yes, most multimeters do not connect the 9V battery to the common because of the design of the typical IC used for the A/D conversion which cannot measure down to the negative battery rail.

    You can however, determine the multimeter's battery voltage by measuring the voltage at both the plus and minus battery terminal using the plus lead (leaving the minus lead disconnected) and adding their absolute values together.
     
    cmartinez and Kermit2 like this.
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