Electronic – Current measurement with a multimeter: how am I doing it wrong

current measurementdc

I want to measure the current draw of a strip of LEDs. This depends on the intensity of the pattern the strips are running so I need to do it in "real time" to get an accurate idea, rather than just do maths from the spec sheet.

I made this cable that should not be in order to insert my multimeter in series with the circuit:

DC barrel socket to barrel-plug cable with positive wire cut

After I plug this in between the (earthed, double-insulated) 12V power supply and LED controller box and clamp the two red wire ends together, everything works fine.

But when I set my multimeter like this:

Multimeter set to Amp range

… and complete the circuit with the multimeter's probes (the red probe on the wire closest to the power supply, black probe closest to the LED's controller box), I get a reading around 3.5A on the multimeter but the controller does not seem to be receiving power and the LEDs don't light.

Any idea what I could be doing wrong?

Best Answer

The 3 jacks on the multimeter are (from left to right):

  • 10 A
  • Common
  • Volt, Ohm, mA, uA, etc.

The correct connection for (high) current measurements is via the Common and 10A jacks.

The setup pictured is wrong, with no lead connected to Common.

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