Is this for real?

[Congoleum Breckenridge]

I can't believe this will work, since it's clamped around both H&N wires.

[Stormin Mormon]

The ammeter I've got requires a splitter, for that reason. I'm suspicious.

[philoÂÂ]

I'm stumped too. Clamp-on meters measure the field in /one/ wire.

If you put a clamp on meter over both wires since current in = current out the sum total would be zero.

[micky]

Maybe you've put your finger on it. The webpage says he "dreamt up Reter as an alternative to traditional clamp meters that fall short."

Maybe the "clamp" isn't over both wires. Maybe the sensor is to the side of both of them, much closer to one wire than to the other.

[mike]

Read the links. The technology exists. But it depends on the physical arrangement of the wires in the cable. Standard flat two-wire cable, maybe. Twisted 3-wire cable of unknown internal dimensions, not so much. I wonder more about what powers the wifi.

In the real world, I expect the unknown cables will be problematic.

How many devices do you have that don't plug in and also have access to the power cable and it's only 2-wire? Water heater? nope Stove? nope Furnace/AC? nope And do I need an iphone to monitor it? KillAWatt is a better investment.

Also in the real world, accuracy isn't necessary. Energy savings is all about relative usage. Less is better.

You need two rules.

1) If you're not using it, unplug it. But you can't unplug devices where this might be useful. 2) Don't use it.

You don't need any measurements to do this. Shorter showers cost less. So take shorter showers.

Mike's metrology maxim... Never measure anything if the answer won't affect your future behavior. I know that a shower costs me about 13-cents. Am I gonna shower half as long to save 6.5-cents??? NO!

I have a device that monitors the utility meter and reports what it thinks. Before I go to bed, I often check to see if it reads 1Amp baseline usage. If it doesn't, I probably left the lights on in the garage.

I figger that in about 20 years, I'll have saved enough money to pay for the monitor...if I ignore the cost of 20 years worth of batteries.

So, my prediction for this device is that gadget lovers will buy it if it's cheap. If they specify accuracy, they're gonna get a lot of them back. If they really explain the benefits, people might realize they don't need one. It's a solution in search of a problem. Fortunes have been made on less...pet rock anybody???

[philoÂÂ]

From my brief look at the website, the device does not exist. It's just an idea looking for money.

[philoÂÂ]

I did not look at all the links, but yes, I imagine if the sensor was placed just right it could work.

Forty years ago I never would have believed one could focus and image from a camera *after* it was taken...but I bought a Lytro which can do that. (After I had fun with it, I gave it to my daughter)

[amdx]

I put a power meter on my water heater at the end of 2008. The family was using $1.73 per day to heat water. Then my daughter went to college, now our hot water costs about $1.01. btw. I didn't save money with her in college :-)

Oh, I don't see how that can work with both wires running through it. Mikek

[Ed Pawlowski]

Most people thought man could never fly to the edge of our flat earth. I imagine there could be a way to do it.

[mike]

You're thinking far field. Up close and personal, near fields have more information that you can get from measuring at more than one point in space.

[RobertMacy]

Fields from a SINGLE long wire drop off as the inverse distance, 1/S.

Ah, but usually you have two wires, one with current + and the other with current -

If the wires are REALLY close together you can see how the plus and minus end up with almost zero field.

However, most wires have a bit of size to them, thus kind of close to them you get 1/S for the positive flow and -1/(S+dS), where dS is that smidgeon of extra distance. now you see, NOT zero field...

What you get here is

1/S - 1/(S+dS) = (S+dS-S)/(S^2+dS*S), for really small dS, throw it away and you get dS/S^2, thus everybody tells you how the field drops off as the inverse SQUARE of the distance.

Now, with judicious measurements made in a 'real' scenario; it is possible to find the current flow in the two wires just by examining the magentic field around the pair, albeit a bit tricky. For example, measuring close, and further, you can find the 'distance' between the wires and calibrate your measurement. In other words, measure current without knowing the exact structure of your wires. and determine the structure of the wires all at once. But, as I said, a bit tricky.

Most clamp on meters use an 'iron' core to distort and 'short' [as in concentrate] the field around whatever it is clamped onto. That type meter dtermines the TOTAL current flowing through whatever it's clamped onto, so if clamped on both AC wires, you get zero.

However, what I described is measuring the field WITHOUT distorting the field [well, not distorting too much]

As an extreme example of the effect of 'spatially' measuring fields to then determine current flow: My magnetic field measuring circuitry has extremely low noise floor. Using that circuitry I once designed a non-contact 'clamp on' multi-sensor system for measuring the independent current flows inside a 25 pair cable. ...for tapping any phone line you want. Each pair when 'active' is anywhere from 10-75mA and produces a noticeable field out to around 3 ft. If your noise floor is low enough.

[RobertMacy]

repost a reply here....

Fields from a SINGLE long wire drop off as the inverse distance, 1/S. Ah, but usually you have two wires, one with current + and the other with current - If the wires are REALLY close together you can see how the plus and minus end up with almost zero field.

However, most wires have a bit of size to them, thus kind of close to them you get 1/S for the positive flow and -1/(S+dS), where dS is that smidgeon of extra distance. now you see, NOT zero field...

What you get here is

1/S - 1/(S+dS) = (S+dS-S)/(S^2+dS*S), for really small dS, throw it away and you get dS/S^2, thus everybody tells you how the field drops off as the inverse SQUARE of the distance.

Now, with judicious measurements made in a 'real' scenario; it is possible to find the current flow in the two wires just by examining the magentic field around the pair, albeit a bit tricky. For example, measuring close, and further, you can find the 'distance' between the wires and calibrate your measurement. In other words, measure current without knowing the exact structure of your wires. and determine the structure of the wires all at once. But, as I said, a bit tricky.

Most clamp on meters use an 'iron' core to distort and 'short' [as in concentrate] the field around whatever it is clamped onto. That type meter dtermines the TOTAL current flowing through whatever it's clamped onto, so if clamped on both AC wires, you get zero.

However, what I described is measuring the field WITHOUT distorting the field [well, not distorting too much]

As an extreme example of the effect of 'spatially' measuring fields to then determine current flow: My magnetic field measuring circuitry has extremely low noise floor. Using that circuitry I once designed a non-contact 'clamp on' multi-sensor system for measuring the independent current flows inside a 25 pair cable. ...for tapping any phone line you want. Each pair when 'active' is anywhere from 10-75mA and produces a noticeable field out to around 3 ft. If your noise floor is low enough.

[Johny B Good]

So, a bunch of electronically selectable and 'steerable magnetic detector arrays' plus a shitload of electronics then?

I suppose it might be do-able today (Hell! who'd have thought we'd have microprocessor chips with transistor counts measured in hundreds of millions (last figure I saw was 135 Million nearly a decade ago).

Seems to be an incredibly 'over-engeered' solution' just to save the need to isolate the conductors to take a current measurement though.

[bob haller]

I prefer analog meters for many jobs. Digital meters are so sensitive the readings can be useless.

I walked under the power line at my home it must be 30 feet in the air, and my digital meter gave all sorts of readings, my analog meter ignored all the electric fields

[trader4]

The part that makes it hard to believe is that this is apparently some little company that doesn't even have a real product to sell yet. It looks like a small, cheap device targeted at consumers. They don't say anything about any new technology, patents, or how they do it. You would think that if this were possible to do with any reasonable accuracy and cost all the pros in the field, eg Fluke would have been out with it long ago. A simple clamp on that you could put around any power cord/cable like that would be an instant seller.

[RobertMacy]

My guess at material cost for using 'available' components, around $200, and DSP processing at much less than $800

Well it's for people who want to do something and not be noticed doing it. Especially undetectably tapping a single phone line from 1 to 3 feet away, through a wall for example, then use a short range 'retransmit' to get it out without tracking the contact back to yourself. package something like that in a wad of tar, so it looks innocuous, like tar dripped from the ceiling onto the cabling, etc.

[philoÂÂ]

That's why I sometimes put a resistor across the leads.

For example, I do a lot of computer work and had some issues with CMOS batteries. They all measured 3.0 volts or above.

I put a 150 ohm resistor in parallel with them and the good ones read about 2.5 v

The ones that dropped to zero, I discarded.

[trader4]

Except that from the link that's clearly not the market being targeted and the price point obviously isn't $3K either

[Johny B Good]

Well, it's obviously something you've given some thought to (hopefully more as a "thought experiment" rather than out of professional involvement).

"Ah, Technology, thou art a cruel mistress with thy double edged sword."

You seem to be suggesting a 'de-weaponised' commercialised application of "Spook Technology". Should we be worried?

[RobertMacy]

Interesting how you went from one shot cost of $1000 to market at $3k. Maybe I should have posted the estimated costs for volume of 100 to 1000

Either way, I wa responding to the idea that intelligently using the field mapping around a cable was exhorbitantly expensive. Back to a single pair current measurement...

could be cost as low as $2 plus housing in 100's quantity.