Cool electrical tool.

[gfretwell]

Amazon got me in an ad but this looks cool

Non contact volt METER (not just test light) with an laser aimed IR thermometer. $40

[Ed Pawlowski]

Would have been very hand over the years for many different circumstances.

[micky]

I have no use for it, but I sure want one.

[TimR]

How is that possible?

[rbowman]

Capacitive coupling to the changing AC fields. Note that it is a tester, not a meter. It will tell you AC is present; and may give you a rough estimate of the voltage.

[gfretwell]

It might be as accurate as a $5 Harbor Fright meter. I have one coming, I will let you know. I do have a variac that I can diddle the voltage from 0~250 and compare the reading to my Fluke meter.

[invalid unparseable]

Hall effect sensor for the AC voltage.

[rbowman]

That's one way to to it. Other designs use a FET on the front end or an op amp. Some add a 555 to get blinking lights.

[invalid unparseable]

That?s no good for a voltage reading rather than just voltage present.

Its not clear if that thing actually shows voltage values or just the temperature values.

[rbowman]

The one the OP linked has a flashing red and blue LEDs to give a rough indication.

Some of them light up for any AC voltage in their operating range, others try for a rough estimate. They're not DVMs by any stretch, just a quick and dirty indication of a hot wire.

[gfretwell]

It turns out that is all this is. It does not really try to indicate voltage beyond 12v vs 120v. There is a different indication for low voltage than line voltage but beyond that it is just a tick tracer. Not as cool as I hoped.