Fluke 123 Oscilloscope

Discussion in 'General Electronics Chat' started by metalworker, Oct 20, 2013.

  1. metalworker

    Thread Starter New Member

    Oct 20, 2013
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    Have a Fluke 123 scope and have a question about measuring current with it: using a 6-volt DC power supply & 1,000 ohm resistor I measure 6 mA with my Fluke 87 meter but with my Fluke 123 I measure 681 mA. Using channel A on the scope I have the red probe (channel A) connected to one end of the resistor and the com probe to negative (series circuit). Scope leads are 1:1 and measure the same on channel B.
    Why doesn't the scope read 6 mA directly on the screen? I'm a new scope user and self-teaching myself.
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    I have a Fluke 123. I will check this out tomorrow.
     
  3. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Sounds like you are shorting past the resistor with your probes and measuring the full output capacity of the battery. Good thing you're only using a weak 6v battery.
     
  4. metalworker

    Thread Starter New Member

    Oct 20, 2013
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    Read a few minutes ago oscilloscope cannot read current directly; the only method is to measure the resistance, voltage and use ohm's law. I thought because current is listed in the Fluke menu it also measures amperage.
     
  5. strantor

    AAC Fanatic!

    Oct 3, 2010
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    I don't have the fluke 123 book in front of me, but IIRC it's a combo DMM/oscope. So it may have the capability of measuring current thru the probes; if so, see my previous comment. If not, then you are measuring total circuit voltage, which is apparently 6.81v. Where is the 681mA coming from? Is that a calculated value or does it say "mA" on the screen?
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    Ok, I had a chance to look at the Fluke 123 and the manual.

    I didn't realize from the post #1 that you are trying to measure current.

    The Fluke is like any other oscilloscope, i.e. it measures voltage.
    In order to measure current, you need a special current probe.

    Assuming that you are using such a probe, you can set the scale factor to
    1mV/A, 10mV/A, 100mV/A and 1V/A.
     
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