I have constructed the following very simple circuit.

enter image description here

I would like to measure the current running through the circuit with my multimeter. I break the circuit as follows and connect the red lead to the jack that says 10A max. I turn the dial to 10 amps.

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When I connect the multimeter, I am reading -0.01 amps or -10 milliamps.

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The following simulation screenshot shows that I would expect to get 65 milliamps.

simulation What am I doing wrong here for there to be a difference between my multimeter and the simulator?


Here is the result using the 200m setting. I am unable to get the led to light up and the multimeter reads 0.0

enter image description here

  • 2
    \$\begingroup\$ In your simulator you have 9V while in the first picture you have 5V.But what confuses is a 55mA difference in current with 4V difference in voltage is very small. \$\endgroup\$
    – Miss Mulan
    May 6, 2021 at 2:45
  • \$\begingroup\$ I'm not sure I'd trust that meter, honestly. It's from a brand I don't recognise, and looks rather cheaply constructed. I wouldn't be surprised if it's out by 5 ULP. \$\endgroup\$
    – Hearth
    May 6, 2021 at 2:46
  • \$\begingroup\$ @MissMulan Would that cause the difference here? Also would I expect to see 10 mA in this case? \$\endgroup\$ May 6, 2021 at 2:47
  • \$\begingroup\$ @s_kirkiles what is the knee voltage of the LED? \$\endgroup\$
    – Miss Mulan
    May 6, 2021 at 2:49
  • \$\begingroup\$ @MissMulan looking at the data sheet it seems to be 1.8 volts \$\endgroup\$ May 6, 2021 at 2:59

1 Answer 1


Fix your 200mA scale blown fuse. ( who hasn't blown their DMM fuse yet? hasn't done enough research )

I’m assuming you know which banana plug receptacles to use...for the 200mA scale...

To measure current accurately, verify R ohms then in the circuit, measure its voltage drop and apply Ohm's Law.

  • \$\begingroup\$ >>> Fix your 200mA scale blown fuse. ( who hasn't blown their DMM fuse yet? hasn't done enough research ) I bought a box of 100 fuses for our lab at work because EVERY FRIGGING TIME I'd pick up a meter that fuse would be blown! \$\endgroup\$
    – Kyle B
    May 6, 2021 at 4:17
  • 1
    \$\begingroup\$ Must be lots of R&D there eh? I remember our female tech. at Burroughs in the early 80’s complaining about having to replace the 1pF FETs on the TEK. Diff probe. Every previous engineer who used it blew one except me. With more than 25V poof, it didn’t stand a chance with any finger charge. \$\endgroup\$ May 6, 2021 at 6:07
  • \$\begingroup\$ Not so much R&D ... rather we are exceedingly generous taking on EE interns from the local colleges.... :/ \$\endgroup\$
    – Kyle B
    May 6, 2021 at 23:27

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