Power meter with LCD display
Power meter with LCD display
Hi, Just last week the electric utility installed a new Centron power meter with a LCD display on it. Very easy to read compared with the old Westinghouse clock type unit that I had to read for ages. (I have to read my own meter every month and phone in the readings myself at this rural location in which I live) I have a question about this meter. With the old meter, one could determine approximately how much current is being drawn by observing how fast the disc inside the meter rotates. Is there any way to read current draw at the present moment with these digital meters?
Quote from a google search:
"Here is the data on how to read 1 Watt-hour from your meter
At 12 o'clock on the face (direction, not time of day) - directly above the meter an infrared light is omitted at a rate of one pulse per watt-hour usage. Okay, probably does not help you.
Your other option is to read that emulator which has 3 dots that turn on and off on the c1sr model. Here is the pattern. First the left goes on, then the middle goes on, then the right goes on, then the left goes off, then the middle goes off, then the right goes off. Kind of like a digital wheel being emulated, cute. Well, that full cycle is 6 watt-hours or to make it simpler, every time one of those dots changes it is 1 watt-hour. Now you can do simple tests of turning on something (like a hot tub, hair drying, drier, tv, light bulb, etc) and count the number of dots you see or if it is going fast the number of cycles (multiple by 6 the result) and you have the energy usage of watt-hours of that appliance during a fixed period. One minute periods worked well for me. If you want full accuracy you can turn off the entire house at the circuit breaker and just turn on the breaker for the one appliance (I did not need to get that accurate). The END. ENJOY."
See the rest here:
http://www.griffmonster.com/miscellaneo ... ading.html
and here:
http://www.itron.com/asset.asp?path=/pr ... 015791.pdf
The data sheet says that there are commumications options that can plug into the meter. The meter also has electronic tamper detection and can also detect if you try to wire it backwards (like driving a car backwards to reduce the odometer reading.)
More if you google.
"Here is the data on how to read 1 Watt-hour from your meter
At 12 o'clock on the face (direction, not time of day) - directly above the meter an infrared light is omitted at a rate of one pulse per watt-hour usage. Okay, probably does not help you.
Your other option is to read that emulator which has 3 dots that turn on and off on the c1sr model. Here is the pattern. First the left goes on, then the middle goes on, then the right goes on, then the left goes off, then the middle goes off, then the right goes off. Kind of like a digital wheel being emulated, cute. Well, that full cycle is 6 watt-hours or to make it simpler, every time one of those dots changes it is 1 watt-hour. Now you can do simple tests of turning on something (like a hot tub, hair drying, drier, tv, light bulb, etc) and count the number of dots you see or if it is going fast the number of cycles (multiple by 6 the result) and you have the energy usage of watt-hours of that appliance during a fixed period. One minute periods worked well for me. If you want full accuracy you can turn off the entire house at the circuit breaker and just turn on the breaker for the one appliance (I did not need to get that accurate). The END. ENJOY."
See the rest here:
http://www.griffmonster.com/miscellaneo ... ading.html
and here:
http://www.itron.com/asset.asp?path=/pr ... 015791.pdf
The data sheet says that there are commumications options that can plug into the meter. The meter also has electronic tamper detection and can also detect if you try to wire it backwards (like driving a car backwards to reduce the odometer reading.)
More if you google.
It would not be hard to build a little gizmo that counts the IR pulses and displays the value on a 44780 LCD. It could be done with a 16 pin PIC. You'd have to figure out if the IR pulse was modulated or not. Less than $10 worth of parts. You might be able to build one with TTL parts if uCs are a challenge to you.
You could get fancier and use RF to transmit the pulse info to a reader with a display that you put in a more convenient location. Of course, you'd need to know uCs...
More interesting but harder is that the device has a zigbee transmitter in it. If they have info on the output format, you might be able to construct a device that reads the data and displays it. Still needs uC expertise.
You could get fancier and use RF to transmit the pulse info to a reader with a display that you put in a more convenient location. Of course, you'd need to know uCs...
More interesting but harder is that the device has a zigbee transmitter in it. If they have info on the output format, you might be able to construct a device that reads the data and displays it. Still needs uC expertise.
Greetings Bob,
"spinning disk" type which (allegedly) is tamper-proof.
Adding solar panels that are grid-tied would require a new
meter, and I'm told the "electronic" meters allow running
backwards.
Probably a different model (I haven't seen one in person),
but I presume it also has the bells and whistles to allow
data to be collected by IR or wireless?
Comments Welcome!
Thanks for the interesting post. We still have the mechanicalBob Scott wrote:Here is the data on how to read 1 Watt-hour from your meter
"spinning disk" type which (allegedly) is tamper-proof.
Adding solar panels that are grid-tied would require a new
meter, and I'm told the "electronic" meters allow running
backwards.
Probably a different model (I haven't seen one in person),
but I presume it also has the bells and whistles to allow
data to be collected by IR or wireless?
Comments Welcome!
Sorry for any confusion. I have edited my previous post to indicate a quotation. I am not the author.Bigglez wrote:Thanks for the interesting post.
Apparently a signal is sent to the power company if any tampering or reverse running is attempted. More information is found in the link and data sheet for the meter.
My father knew a guy who would rewire his meter to run backwards for 1 week per month during the depression. Everyone was poor then.
The spinning disk meter I have can apparently be electronically read. The PG&E meter reader just waves a yellow stick near it to get the data. I have no idea what is the communications or data protocol. Can't see any obvious IC chips in the meter from outside. He does need to be close at most a couple meters.
PG&E does not buy back power from residential customers so presently has no need for meters to run backward. Tampering also includes hotwiring so that it does not run at all while you consume.
PG&E does not buy back power from residential customers so presently has no need for meters to run backward. Tampering also includes hotwiring so that it does not run at all while you consume.
Hi there,
I dont know what kind of accuracy you are looking for, or what kind
of devices you are running in your home, but there is a 'rough'
conversion you can use.
1 watt hour is the same as 3600 watt seconds, and as you know
the watt=E*I, so you could log the change in watt hours (assuming
your new meter logs that resolution) and the seconds it takes to
get to that new reading, subtract, and divide by 120 (assuming you
are using 120vac line power).
For example, if you read 1 watt hour increase after 1 second that means
3600 watt seconds, which is approximately 30 amps.
If you read 1 watt hour after 2 seconds then the current draw is
half that, or 15 amps.
If you read 2 watt hours after 1 second then the current draw is
twice that, or 60 amps.
I guess we get a simple formula out of this...
Amps=15*energy/time, or
Amps=15*watthours/seconds
which in words, is:
"The amps equals fifteen times the watt hour reading increase divided
by the time (in seconds) it took to get that increase".
This is going to be approximate because we dont know the current
phase angle of whatever you are running.
I also have to wonder why you need to know the total current draw
of your home...
I dont know what kind of accuracy you are looking for, or what kind
of devices you are running in your home, but there is a 'rough'
conversion you can use.
1 watt hour is the same as 3600 watt seconds, and as you know
the watt=E*I, so you could log the change in watt hours (assuming
your new meter logs that resolution) and the seconds it takes to
get to that new reading, subtract, and divide by 120 (assuming you
are using 120vac line power).
For example, if you read 1 watt hour increase after 1 second that means
3600 watt seconds, which is approximately 30 amps.
If you read 1 watt hour after 2 seconds then the current draw is
half that, or 15 amps.
If you read 2 watt hours after 1 second then the current draw is
twice that, or 60 amps.
I guess we get a simple formula out of this...
Amps=15*energy/time, or
Amps=15*watthours/seconds
which in words, is:
"The amps equals fifteen times the watt hour reading increase divided
by the time (in seconds) it took to get that increase".
This is going to be approximate because we dont know the current
phase angle of whatever you are running.
I also have to wonder why you need to know the total current draw
of your home...
LEDs vs Bulbs, LEDs are winning.
Greetings Hakeup,
we recently went to bid for grid-tied solar on our home.
Cites furnished on request.
The process is to replace the old meter with one that
registers in and out power, and displays the net. The
utility is required to give one for one credit per kW-hr.
The billing plan changes from residential (E-1?) to an
annual plan and one bill per year (or quarter, I forget).
The utility will not purchase surplus power, but
does credit each kW-hr generated by solar.
Additionally, the state issues a one time rebate if the
system meets their (somewhat tight) specs, the
bottom line is about 40% the cost of installation.
Unfortunately, it's still a rich man's project with
approximately $60k of costs and about a ten year
pay-back.
Comments Welcome!
This statement is not true. I'm a PG&E customer andhaklesup wrote:PG&E does not buy back power from residential customers so presently has no need for meters to run backward. Tampering also includes hotwiring so that it does not run at all while you consume.
we recently went to bid for grid-tied solar on our home.
Cites furnished on request.
The process is to replace the old meter with one that
registers in and out power, and displays the net. The
utility is required to give one for one credit per kW-hr.
The billing plan changes from residential (E-1?) to an
annual plan and one bill per year (or quarter, I forget).
The utility will not purchase surplus power, but
does credit each kW-hr generated by solar.
Additionally, the state issues a one time rebate if the
system meets their (somewhat tight) specs, the
bottom line is about 40% the cost of installation.
Unfortunately, it's still a rich man's project with
approximately $60k of costs and about a ten year
pay-back.
Comments Welcome!
Greetings Mrai,
routine that gave kW-hr for inputing revs of the disk....
Comments Welcome!
I have fuzzy recollection of an hp programmable calculatorMrAl wrote: I dont know what kind of accuracy you are looking for, or what kind
of devices you are running in your home, but there is a 'rough'
conversion you can use.
routine that gave kW-hr for inputing revs of the disk....
AFAIK, the OP is required to read their own meter (rural location).MrAl wrote:I also have to wonder why you need to know the total current draw of your home...
Comments Welcome!
My primary interest is being able to detect whether or not any current is being drawn by my electrical devices and to have a rough idea how much. A year and a half ago, suddenly my monthly consumption went up by 20%. I quickly isolated the fault by turning off circuits and looking at the rotating disc in the meter to see how fast it was turning. I want to know how to do this with the new meter in case I have another electrical problem like this in the future.
The culprit was a large old freezer in an outbuilding. The freezer's thermostat got stuck and it was running 24/7. This happened in November 2006 and the freezer shouldn't have ran at all as here in Manitoba the temperature is around +15F days and around 0F nights this time of year. I had no need to go to this freezer for a while and was unaware that it was running continuously.
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