Monitoring electricity consumption of a device?

Why won't a regular watthour meter like the electric company uses work?

And if it won't work, aren't you concerned that the electric company will come after you for using power in a way they can't measure?

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and ask the same question. You will almost certainly have to use a data collection system sampling at a fairly high rate. I don't believe there exists any simple meter that will integrate the usage, so you need the digital equivalent of a continuous chart that will do the integration for you. Of course, the power company's meter does that, if you want to spend the money and record the readings by hand.

So, does this overlooked technology make Ohm's law obsolete? Why can't you calculate the energy usage? You know the resistance of the heating elements and the amount of time you need to achieve the temperature rise in the furnace and the line-in voltage. What else do you need?

Unless I'm missing something, Kilowatt Hours over a given time will give you the bottom line. Buy a KWH meter. If you're correct, it will pay for itself. IIRC, you are off the grid? If your place was ever on the grid, "borrow" their meter for a while.

Ohm's law works fine but he's only firing at a fraction of the time once he's up to temp. This varies by the surrounding conditions. A KWH meter will tell the real story. My kiln draws 56A when it's on full bore, but seldom is it doing that.

On most controllers we can see what percentage of full power is being applied. He could see what percentage each furnace uses to maintain a given temp (2100F?) at like ambient conditions.

A couple things: My controller is always set at 100% output signal; it's the P.A. scr that varies the output. If you put an ammeter on it, even while the furnace is at equilibrium and totally thermally stable and idleing, the current jumps all over the place, and that's normal. I do think a regular watt hour meter is what's required but like Mike Firth says I'm not sure if I can get one that will work only on the furnace circuit and also be compatible with the SCR. Yes of course the power company meters the usage, and I'm certainly not trying to cheat them. But it is noteworthy that at my other studio in Hawaii the meter always had trouble and they never really figured it out.

Jack my house in Hawaii and coldwork shop is off the grid (solar and bio-diesel) but my former hotshop over there never was. Here in Oregon I have grid power. Also

The technology I'm using has to do with insulation, not the energy input. The reason I need to monitor the power is that I don't believe surface area and heat loss equations are going to provide a good real world analysis. Plus, I suck at math. I have a way to vary these insulation qualities while keeping the other parameters (mostly) the same. So if I can accurately measure usage...

Kilowatt Hour meter, yup, believe it or not, I have one. But I don't know if it will work for your application. I was in a building that we shared the electric bill, thought I was getting screwed over, so I put a sub meter on the pieces of equipment that was running so I could tell what was "my share". No longer need it, still have the meter, you would have to get your own hook ups for it, but I know it was pricey, we can negotiate if you need it, anyone.

Moonraker Only part of each cycle is being used in a phase shift SCR controller.

he were using zero crossing trigger SCR or SSR, and they were fired not very often, then simply adding a small analog clock to the circuit would let your method work- the number of minutes the clock was on gives a good idea of the actual power used (% of day) [or a digital timer with electronic on-off. I have analog, I don't own a digital timer.] Jfuse If you are interested in the details, you are going to need to do data collection on a millisecond by millisecond basis, which is considered slow in the Sensors world. And you are going to want to feed it into a file so it can be loaded into Excel for averaging, totalling and graphing. However, I do not follow what you say about your controller being at 100% output. Something has to be controlling the Phase Angle SCR and that is usually called a controller.

Sure, how much did it cost? I'll try and find out if it will work with the scr, or what modifications might be needed. What can you tell me about brand, specs, etc.

I have had it, un-hooked and on the shelf, for 15 years, looks new and worked fine when it was attached.

You have to bear with me a bit here, because a friend that is an electrical engineer hooked it up for me. I had a 440 air conditioning unit, the other tenant also had one, they were connected to the same meter, we wanted to know if the bill was being split according to use or just split 50/50. Enough of that, there were 3 coil like donuts that encircled the hot wires and produced a reading.

I will attempt to get a model number and details for you, if this address is your email, I'll send a note.

This may be of interest to you:

've not used one, but I had bookmarked the page, as it had gotten prettygood reviews in another NG I read regularly.Alternately, find a rundown, abandoned house with a meter still in the box,and borrow it (just kidding, of course). If it's really old, the power co.would replace it anyway. Maybe even ask a power co employee if they can getyou an obsolete meter. Sometimes the rural electric coops are easier todeal with. They are all changing over to the meters that can be read fromthe truck via RF.

HTH, Joe

snipped-for-privacy@maui.net wrote:

Hi Mike. As Jack pointed out, many of us have controllers that are sophisticated enough to allow percentage-wise control of the output signal. This can be used for various purposes, notably in our case, to reduce watt-loading of elements. For example if your heater draws 60a, you might set your output signal at 50% so that the elements are not taxed at their maximum. Simply, a way of current limiting from the controller. I don't use that feature however, because my scr has a built in current limiter that can be set.

The analog clock will work with a mechanical relay or a mercury relay. I would be very skeptical about it working with a burst-fire ssr under any circumstances, but wtfdik.

I really have to avoid a very complicated system, Mike. If it is as you say, and a particular type of current meter won't work, I'll just run the furnace and know it is very efficient but not quantifiable. Because, I don't build furnaces for a living, and I'm not writing a dissertation. I have to make glass for a living.

PS. Errata in reference to the clock I meant an *SSR or a burst fire SCR.*

I would be very skeptical about it working with a burst-fire ssr under any circumstances, but wtfdik.< Works fine on my rig. The signal coming off an SSR with zero crossing (not phase control) is exactly what goes in. If the not too radical assumption is made that it starts pretty quick at power on and only coasts a bit on power off, then it records the length of the on-time. My controller tends to stay on till the controller sees how the power affects the temp (it "learns") and then at temp, it stays off for many seconds and on for a few seconds, so the analog clock works. At one time, I stood there with a stop watch and timed the indicator light and found the watch and the clock were matched close enough for my purposes.

Ummmm....that's what fans are made for.