What is an EMF meter really for?

I did a search and found loads of information. Try it !

KenW

What is your definition of "real"? Would anything sold by Gwyneth Paltrow qualify? There are reasons for wanting to know what the electric field strength is...

EMF (electro-magnetic field) can be anything from 60 Hz power line radiation, to microwave emissions. The real EMF meters were designed to help measure specific EMF fields for measuring things like cell phone SAR (specific absorption rate), unwanted emissions for FCC type certification, radio/TV broadcast station antenna pattern, EMC (electromagnetic compatibility) testing, and personal RF safety such as might be encountered when working on a radio tower. Some typical applications:

Typical equipment:

The low cost junk sold online is at best a crude imitation of a proper EMF meter mostly because they do not produce meaningful measurements that can be useful for design, installation, testing, and verification.

If you purchased a junk EMF meter like this:

Good luck

I won't claim a fresh brain but the advertising hype on these products did peg my BS meter.

On the other hand, at about $20 for some of the cheapies, would they be useful to avoid hitting a power line drilling through a wall or digging in the garden? You mentioned 60 Hz power line radiation.

Well, maybe a baked brain.

No. The AC wiring in the wall is too narrow and probably too far away for the junk EMF meter to accurately locate it.

I have one of these, which has an AC wiring locator feature:

One catch. These tend to use 9V batteries, which are becoming rather expensive. I've been switching to rechargeable LiIon 9V batteries:

In snipped-for-privacy@4ax.com Jeff Liebermann snipped-for-privacy@cruzio.com writes: [snip]

I hope you're not one of the old fashioned types who still hang on to pi - surely you've converted to tau like all the cool people?

At the simple end, a Field Strength Meter- antenna, diode, meter; at 60Hz you'd need a big antenna, probably a coil.

Hardly. I prefer my power delivered as DC as Edison and the other patriarchs of power transmission intended it. For a time (early

On your second link it seems that DC stands for "district of Colombia" :-)

Jeff:

Either you have a rare sense of humor, or you are genuinely certifiable - or, hopefully, both.

Peter Wieck Melrose Park, PA

Parts of NYC had DC utility power as late as the 1990's. While Con Ed stopped new hookups 1960ish, they kept the legacy wiring live a lot longer.

My 6 story apartment building with 28 apartments had regular AC, but _ALSO_ had DC coming in for the elevator (a pretty common situation) and ... had an "unmetered" (flat rate) separate low current feed dedicated for the fire alarm.

A friend of mine lived in a similar apartment building on 110th and Columbus Ave 1975ish, and believe it or not... the rooms there had standard outlets, some of which provided, sit down for this... 120V **DC**. Yes, identical.

We figured it was cheaper for the landlord to pay off the building inspectors than to rewire...

Note that since we're talking 1975 (and earlier), people had many appliances (basically incandescent lamps) which would, indeed, work ok. But don't plug in your record player.

Would the liquid mercury based wall swiches (remember them?) have worked ok?

You're right. I screwed up. I thought they were installing an underground DC power line. Sorry.

Amazing. I would have thought that 120V DC would have disappeared long ago. I did try 120VDC on my house electrical system to see what would happen. It was similar to the 12VDC arcing and contact welding that I experiences with 12VDC. I also got a few shocks. 120VDC was quite different from a 120VAC shock. I think I may have pulled some ligaments or tendons from the rapid muscle contraction.

I don't know. I didn't have any mercury switches and none of the stores had them for sale. I would guess(tm) that the major problem was the glass bulb exploding from something that produces hot gases from the arcing. No oxygen, therefore no combustion or burning. With just mercury and some kind of contacts, there's nothing that can burn, so I guess it might be safe. However, I would be worried if vaporized mercury could sustain an arc across the contacts, which would not be a good thing. Probably a bad idea.

I thought that mercury had been banned in consumer products in the

The phone company in NYC had 105v 20cps for ring tone sent to feeds at least till 1973 when I quit. Probably for old switchboards and pbx's. I got zapped a few times in backyards testing phone troubles. IT WAS HOT !!

KenW