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Battery and resistance

  1. Aug 7, 2014 #1
    Hi every one,

    I placed a multimeter probe across the terminals of a 1.5 v alkaline battery and saw 2 M Ohms, I did the same across a mV power supply at 1.5 volts and got little below 1.5 K ohms. I dont understand what makes them have diffrent resistance, and exactly why?

    I did this because I had an odd situation with a SIL 2 (safty integrity level) rated gas analyser, the analyser would only work with a real sensor or a battery at correct voltage, but not a simulator (e.g mV supply).The diffrence as it seems is the sensor has very high impedance. So i measured the resistance of the battery and the supply, and now i am confused why the battery shows such high resistance.
     
  2. jcsd
  3. Aug 7, 2014 #2

    berkeman

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    Staff: Mentor

    That's not how you measure the output resistance of a voltage source. The DMM resistance measurement is for passive devices, not for active sources of voltage or current.

    Instead, make 2 output voltage and current measurements using 2 different resistors, and solve the 2 simultaneous equations for the source resistance of the voltage source. Are you familiar with that measurement technique?
     
  4. Aug 7, 2014 #3

    jim hardy

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    2016 Award

    ttsky: You might want to read up on how an ohmmeter works.
    http://en.wikipedia.org/wiki/Ohmmeter

     
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