Interesting Fluke meter

[ppppenguin]

http://www.fluke.com/fluke/uken/electric...?pid=55986

How on earth does it work as a current meter without surrounding the cable?

[Mark Hennessy]

Hall sensors, I'd guess...

For a similar puzzle, try this: http://uk.rs-online.com/web/p/clampmeters/4955459/

We have one here. Not terribly accurate, but not bad. Sadly discontinued...

[ppppenguin]

And how on earth can it measure the current in one core of a multicore cable that's carrying both flow and return current?

[Mark Hennessy]

From the datasheet:

Unlike conventional clamp meters, the MMC850 has a complex array of Planer magnetic sensor coils to calculate the current flowing in the conductors of multicore cables with either 2 or 3 cores, and in either flat or round section cable, up to 100 A.

[ppppenguin]

All sounds terribly clever. I wonder if it can ever be decently accurate, especially when allowing for all the odd angles you might offer it up to the cable.

[Refugee]

The best test would be to measure a cable in an open space and try it an a wide range of angles.

[Nick]

Could well be a Rogowski coil...

I have a number of these for monitoring high current & high frequency pulses in big solid-state Tesla coils (2000A @ 100kHz)

[ppppenguin]

I'd forgotten about Rogowski coils. Never used one but they are a clever idea.

Presumably these open jaw and multiconductor ammeters won't work with DC. That needs Hall Effect devices or a fluxmeter. I have a lovely set of Crompton Tongtest which are fluxmeters.

Link is only for illustration: http://www.ebay.co.uk/itm/CLAMP-METER-CR...1275704841

[Mark Hennessy]

I'd forgotten about Rogowski coils.

I freely admit that I hadn't heard of Rogowski as a name. Learn something new every day

[Terry]

That makes two of us - at least!