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Multimeters help

  1. Dec 27, 2013 #1
    I am a PC Repair Teck and I need a good Mulimeter.

    But I am going to be taking Readings of House Hold Voltage and Currents as well.

    So I need it to be able to be able to Read A.C. Amps up to 15 Amps and maybe above.

    I need it to Take Resistance Readings from as Low as 200 mOhm to 20 MOhm.

    And I would like it to have an Imput Impedance of 10 MOhm.

    I need it to take Continuity Readings to.

    I can not find one for this and even the High end ones wont let me Read A.C. Amps up to 15 Amps.

    Can anyone help?
  2. jcsd
  3. Dec 27, 2013 #2


    Staff: Mentor

    You'll probably need to get two meters, since I don't think there is one that will do everything you're asking. To read household currents, get a clamp ammeter. Sears has one that will read up to 400 A. for about $50 (http://www.sears.com/craftsman-digital-clamp-on-ammeter/p-03482369000P). If you do a search for digital multimeters, you'll probably find one that can measure resistance in the range you need.
    Good luck!
  4. Dec 27, 2013 #3


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    I had one of these before, they go up to 20A. They're kind of shitty, and I used my fluke43b for almost all my power stuff. Google the spec sheet, I think the input impedance is a bit lower than what you want. It's greater than 7MΩ though. The price is also really good, however.
  5. Dec 27, 2013 #4


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    Two meters, that are simple to use and cheap to replace if they get damaged, might be a better option than trying to find one that will do everything you want. For example one designed to measure domestic (or industrial) mains power, and another for electronics.

    You don't say why you want to measure resistance down to 200 mOhms as compared with just a continuity test, but bear in mind that measuring small resistances accurately is not just a matter of putting a test probe on each end of the resistance. You need to eliminate of compensate for stray resistance (e.g. the meter lead connectors), stray induced EMFs, accidentally creating thermocouples between different materials in the measuring circuit, etc.

    if you want to measure small resistances for safety checking on mains-powered equipment (e.g. checking earth connections etc), you really need a test meter designed for that task.
  6. Dec 27, 2013 #5
    Ok this is the Meter I would like to get first.

    I need to stick the Probes in an House Hold Outlet to Read the Current.

    Do they have this type?
  7. Dec 28, 2013 #6
    Wow. This tells me you should not be messing with this stuff. Also tells me you might not actually know what you need. Measuring current is an operation that involves breaking the circuit and inserting the meter is series. Sticking the probes and an outlet as you describe would be a voltage measurement. Try this with a meter set to measure current and you will likely cause smoke and wreck your meter.
  8. Dec 28, 2013 #7


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    The leads will melt, fuses will blow, I've seen it happen before.

    The better alternative to measure current is get a clamp like the one posted above. Clamp yourself onto the plug of the equipment drawing the current you want to measure to take your reading.
  9. Dec 28, 2013 #8
    Ok if I get a Clap A Meter and put it around say the cord coming from a TV Set going to the Outlet it will give me the Crrent the TV Set is Drawing right?

    I want to see the amount of current the Outlet is putting out.
  10. Dec 28, 2013 #9


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    More or less.

    The outlet doesn’t put out any current on its own.
  11. Dec 28, 2013 #10
    You have to clamp it around only ONE conductor in the cord. Clamping around both will measure the current in both wires, which are equal in magnitude but opposite in polarity so they will cancel and give you a net reading of zero.
  12. Dec 28, 2013 #11
    Well I know an Outlet can Supply 120 Volts at 15 Amps.

    And what you plug into the Outlet will Draw what it needs.

    I know the Amps is how many Electrons are moving past One Point in one Second.

    Now if I want to see how many Volts an Outlet can Supply I can use a VoltMeter.

    But a Clamp A Metter will just tell me what the Device pluged into it is Drawing.

    How can I see how Many Amps an Outlet can give?
  13. Dec 29, 2013 #12


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    Hi biferi. There is no safe way to measure such a maximum current capability, but fortunately you should never have a need to, anyway. The current rating of every power outlet is predetermined by the physical installation, and is a function of the hardware (household wiring, sockets and switches, and fuses or circuit breakers). The maximum current rating of every outlet is a regional standard and is usually shown on the outlet itself and/or the fusebox. Figures of 10 amps and 15 amps are common. The total current allowed for any particular household installation is also predetermined by the cabling leaving the main switchboard; residents can't simultaneously load all outlets to their rated (maximum) currents and still expect the switchboard circuit breakers won't trip!

    If an outlet is suspected of being faulty or is unable to supply its expected rated current, then you must call a properly qualified and licensed electrician to investigate the problem and fix it. There is absolutely nothing you yourself can attempt to do about the fault, in such cases.
  14. Dec 30, 2013 #13
    Not sure what you are saying here. The first statement implies you do not need the last question answered. Are you saying you want to load test an outlet or circuit? What are you expecting to happen when the circuit can no longer supply the 15 amps? I suspect that you do not fully understand what you are asking. There is NOTHING WRONG WITH THAT as long you accept it and take steps to correct those misunderstandings. I am guessing that with every post made here you have new questions and are more confused. That's ok. We are here to help.
  15. Dec 30, 2013 #14

    Vanadium 50

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    This thread has many similarities to "what is the right kind of bubble bath for me and my toaster".

    Please try and impress on the OP that what he intends is a) dangerous, and b) futile, since it doesn't measure what he wants.
  16. Dec 30, 2013 #15
    I sense that the OP wants to be able to measure something about current and does not truly know how or what.
    I got my first multimeter as a young kid and thought if you want to know the voltage of a battery (AA for instance) you set the meter to volts and hook up the probes. Mistakenly, I thought if you want to know current you do the same except set it to current. Glad I never tried it with a car battery. It sounds as if this is the same mentality as the OP. He just doesn't fully grasp voltage and current measurement.
  17. Dec 30, 2013 #16


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    The best way to determine the max current is to go to the fuse (or breaker) box and look at the fuse or breaker rating.
  18. Dec 30, 2013 #17


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    In the scenario you describe, the outlet is putting out precisely the same current as the TV set is drawing¥. There is no need to try to measure it a second way.

    ¥ assuming the TV is the only device plugged into that particular power socket
  19. Jan 6, 2014 #18
    In answer to the OP's original question, check out Fluke Meters.
    They are some of the best on the market. You will need a clamp-on for the current levels you quote, but they have a line of clamp-ons that also have all the other multimeter functions.

  20. Jan 15, 2014 #19
    And 15 amps at mains voltage is enough to kill you.

    OP just stay away from this. You don't have enough background to ask the right questions let alone do measurements.

    I suspect you want to measure power consumption from a PC, in which case I would use something like
    Last edited: Jan 15, 2014
  21. Feb 1, 2014 #20
    I also agree that you must stay away from this stuff op.

    Also the max current your outlet can provide depends on two things, wire gauge and the circuit breaker. If the circuit breaker is properly sized, the max current allowed will be below whatever the breaker is rated at.

    If the breaker is faulty and does not trip as it should, the max current you can pull is dependant on the gauge of the wire. Basically, the thicker the wire the more current you can pull before the insulation burns out and the circuit shorts.

    You also have to consider the insulation, some wires can handle more current than others based on the insulation on the wire.

    I work with electricity on the 24v, 120v and 480v 3phase levels so I can answer questions pertaining to those three.
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