Plus/minus sign on clamp meter jaw

[bitwelder]

The other day I received my latest equipment purchase, a mini-clamp meter UT210E, which has been described on this thread: https://www.eevblog.com/forum/testgear/a-look-at-the-uni-t-ut210e/msg560006/#msg560006

On the left clamp 'jaw' there is a plus sign on the top side, and a minus sign on the bottom side. See e.g.



What's its purpose?

[dom0]

Nominal direction of current.

[belasajgo]

It has to do with DC current measurement and the direction of the flow of current in the wire (polarity of the magnetic field). If the flow of current is in the other direction, you will get a negative value.

[Fungus]

What's its purpose?

So you can tell which way the electrons are flowing.

(If the meter shows a negative number then they're going the opposite way to the markings on the clamp)

[bitwelder]

Thanks!

[jeroen79]

And the + means current coming out of the clamp?
(and electrons going in)

[bitwelder]

Simple test: test lead going from the + terminal on the bench PSU into the clamp from the top (+) side, to a small load and return to the - terminal on the PSU => meter measures positive current
Insert + wire from the bottom of the clamp => meter measures negative current

[Fungus]

And the + means current coming out of the clamp?
(and electrons going in)

Good question! And an amazing opportunity to do an experiment!! I wouldn't let this one escape if I were you...

https://xkcd.com/567/