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Explanation on Shunt resistor from meter

  1. Apr 23, 2013 #1
    I know meter shunts are used to direct most of the current away from the meter coil but my question is if you direct most of current away from the coil, how is the meter measuring the current flow accurately.

    Im kinda slow in the head so no complex fried banana explanation. tnx
     
  2. jcsd
  3. Apr 24, 2013 #2
    Can someone explain this to be quick, or are you all also slow in the head
     
  4. Apr 24, 2013 #3

    vk6kro

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    A meter shunt diverts an exact proportion of the total current away from the meter but also an exact proportion goes though the meter.

    So, if it takes 1 amp to make the meter read full scale, it will take half an amp to make it read half scale. Similarly, the meter reading is always proportional to the actual total current.
     
  5. Apr 24, 2013 #4

    vk6kro

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    This comment is unacceptable. You can say what you like about your own intelligence, but it is insulting and outside Forum rules to assume anyone who doesn't choose to answer your question is stupid.

    Answering questions is purely optional.
     
  6. Apr 24, 2013 #5
    Vk6kro thank you, I don't mean stupid, I mean slow typers. But I still don't understand your explaination but thanks
     
  7. Apr 24, 2013 #6

    vk6kro

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    Suppose the meter takes 1 mA and has a resistance of 900 ohms.
    When 1 mA is flowing, the voltage across the meter is I * R or 0.001 amps * 900 ohms or 0.9 volts.

    If you put a 100 ohm shunt across the meter, then the current through the shunt for a full scale meter reading would be 0.9 volts / 100 ohms or 9 mA.

    So it now takes a total of 10 mA to get a full scale deflection on the meter.

    Can you see that it takes 5 mA to get a half scale deflection on the meter?
     
  8. Apr 24, 2013 #7

    jim hardy

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    Think of the meter as a resistor.

    Surely you can solve how current divides between parallel resistors?


    Changing them to admittances helps visualize it.

    Ohm's Law - it's more than just a suggestion.
     
  9. Apr 25, 2013 #8

    sophiecentaur

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    That can only be taken as an insult. "In the head" doesn't refer to typing speed.
    Afiac, you can solve your own problems. Your main one is to learn to be polite when you need to know something and to apologise when you have offended someone.
     
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