0

I've noticed an oft reported 'tingling' sensation when using my Macbook Pro and was curious to measure how much electricity was running through my body while using the laptop plugged in like so:

GROUND -(black lead)- Multimeter -(red lead)- Left Hand - Right Hand -- Laptop

I measured: 83v 0.032mA

When the laptop is unplugged, the tingling completely disappears and it reads: 11.3v 0mA

Unfortunately I can't find the grounded power cord to test.

Is this reasonable? The amperage is incredibly low, but it's definitely a bit disconcerting (perhaps just the reality of electronics) to have voltage + current running through my body like this.

I am in Germany (single phase 220V) and using a True-RMS Multimeter in AC mode.

waffl
  • 101
  • 1
    When you say "I measured 83v 0.032mA," do you mean that you set your multimeter to voltage mode and it showed 83 V, and then you changed it to current mode and then it showed 0.032 mA? Or did you have it set to some mode which shows both voltage and current mode at the same time? – Cassie Swett Feb 02 '22 at 21:41
  • That's correct, I measured voltage first, then switched the leads over and measured amperage next – waffl Feb 02 '22 at 21:44
  • check your grounds. might need to run an aux ground, like an alligator clip biting a usb ground (that's how i fixed the buzzing of an external hifi playing lineout audio). – dandavis Feb 02 '22 at 21:45
  • @waffl My Microsoft Surface Book reads about 60 VAC when I'm touching its case and feeling a tingling taking place. So that's a "loaded" voltage using one side of the US split-phase system. Their plug is two-prong and doesn't include a separate ground lug. Worse, both prongs are the same smaller size, so the plug can be easily reversed. Plugged in one way, I get the 60 VAC reading and a tingling feeling. Plugged in the opposite way, almost no VAC reading and no tingling at all. Went through filing a report with Microsoft. Received a "that's okay, don't worry" from them. – jonk Feb 02 '22 at 22:30
  • @jonk But that's not fine. Having capacitively coupled 60VAC between two devices is not exactly fine. Imagine plugging in a USB device or display, and the grounds disconnect for a sratchy microsecond, and you've blown an important data pin and maybe whole laptop chipset or the other device (USB drive you use for backups) damages so that it will never run again. Worst case, both devices. Having ungrounded devices like that is just garbage, not seen much in these 240V 50 Hz parts of the world fortunately, likely due to legislation etc. – Justme Feb 02 '22 at 22:46
  • @Justme I don't disagree. That's why I filed a complaint, formally, with Microsoft. They gave me their response. Which didn't really take me by surprise. The US is a "buyer beware," because the US gov't is pretty much run by larger corporate interests. There were better times. But not so much, now. – jonk Feb 02 '22 at 23:14

2 Answers2

2

Yes, the readings and tingling are completely reasonable when using a device that requires earth/ground and plugged to non-earthed/non-grounded mains socket.

The mains input filter needs ground to work or device may float at about half mains AC voltage due to capacitors to earth/ground.

It also most likely says "do not plug into ungrounded outlet" or "only plug to grounded outlet" so that is what happens when electrical devices are used against instructions.

Justme
  • 127,425
  • 3
  • 97
  • 261
0

IEC 950 sets limits for allowable leakage current at 0.25mA for double insulated equipment, which I believe your laptop would fall under. The testing methodology is different than what your setup is (it doesn't make any assumptions on body resistance).

vir
  • 14,718
  • 13
  • 28