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Measuring current from a charger

  • 20-05-2008 07:33PM
    #1
    BoB_BoT
    Registered Users, Registered Users 2 Posts: 1,835 ✭✭✭


    Hi all,
    I'm trying to measure the current coming from a laptop charger. But I'm not 100% sure on how to do it. I'm using a multimeter, set correctly, set the amps to dc and "10", however how do I create a circuit in which to test? I know you have to break the circuit to measure the current flowing through.

    I can't have a makeshift connection going to the laptop and break that connection, as I think the charger may be faulty.

    Anyone have any suggestions on how to do this, or am I going about it the wrong way?

    Thanks :)


Comments

  • #2
    10-10-20
    Registered Users, Registered Users 2 Posts: 8,655 ✭✭✭10-10-20


    You have to have a break in the circuit - which is then completed by the multimeter - to be able to measure current. Don't short the two feeds anyhow - that's a sure-fire way of damaging the powersupply and/or multimeter.


  • #3
    fishdog
    Closed Accounts Posts: 1,113 ✭✭✭fishdog


    You have to have a break in the circuit -
    I would not like to cut anything! Why not use a volt meter?? If you know there is voltage, the laptop is a resistance, so a current will flow.

    The best solution is borrow a similar charger and see if the problem is fixed. I am sure a laptop shop will lend you one in the shop if you act like you may be a good customer. It will only take a minute.


  • #4
    spadder
    Closed Accounts Posts: 985 ✭✭✭spadder


    You can get a device that reads current by placing it around the cable with out breaking the cable.
    If you know a sparks, he probably has one.

    Do you think your power supply is faulty?

    It shoud say on the back of the charger what the amp draw is?


  • #5
    mossym
    Moderators, Sports Moderators Posts: 8,766 Mod ✭✭✭✭mossym


    without the load of the laptop the charger won't be sourcing any current anyway, so will be very difficult to do what you want. you could get a passive load and see if the charger can source the right current.


  • #6
    Stoner
    Registered Users, Registered Users 2 Posts: 10,952 ✭✭✭✭Stoner


    Clamp amp meters are not very sensitive I dont think they are great at under 2 Amps , but maybe there are better ones out there, a power line analyser will do this, you plug it into the wall, and the pluf a device into it, it will tell you what current is being used.

    The charger will have its own current due to electrical loss etc, and the laptop will have to be on and charging for you to see what current it is drawing when it is in operation mode


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  • #7
    fishdog
    Closed Accounts Posts: 1,113 ✭✭✭fishdog


    You can get a device that reads current by placing it around the cable with out breaking the cable.

    This is a grip on amp meter. It will only work with AC. The output of your charger is DC.

    This is a simple problem, with a simple solution:
    borrow a similar charger and see if the problem is fixed.


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