Electricity meter question.

I have one of the relatively modern electricity meters with a digital display and when I went to read it today to send in the reading, the display was reading alternately the power consumed and "rEd". Additionally a red led is permanently on.
The make of the meter is 'Ampy' - Black and about 100 x 150 x 40mm
Can anyone confirm what this means please?
I have recently had a solar PV system fitted which can feed power back into the grid. The meter was not changed to accommodate this (instead I have my own generation meter) so I wonder if it is just an indcation that the meter has tried to run backwards which would normally happen if someone was trying to fiddle the meter reading but in my case just shows the Solar PV has been generating more power than I have been consuming.
TIA
Bob
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Bob Minchin wrote:

I know it is bad form to reply to your own posts but it might help someone.
I have found the answer here http://universalmeterservices.co.uk/store/images/5193.doc
The red light either flashes every 1 watt-hr consumed or stays on continuously when the power being consumed is below a preset level.
The display flashing rEd is showing "reverse energy detection" which would normally mean fraudulent use but in the case of power export from microgeneration schemes (PV, wind etc) is legitimate.
In my case, when the light is on continuously it means that I am generating more power than I'm using - this is confirmed by the display reading now being identical to the one I took 8 hours ago.
According to the manual, the meter has a separate register measuring exported power although the reading is not displayed.
Bob
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On Apr 20, 5:10 pm, Bob Minchin
Meter Memory
All the meters data is recorded in a Ferroelectric Random Access Memory (FRAM) under the control of the microprocessor. All the kWh registers are stored in the FRAM and are updated every 1/100 th of a kWh. The FRAM is guaranteed for a minimum of 10,000,000,000 write cycles
WTF? Core memory?! 8-)
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Andy Dingley wrote:

Yes I found that difficult to credit but I suppose it maybe used to meet a possible regulatory requirement for N years retention with no power connected??
Having looked further, I think it is the 10,000,000,000 write cycles that makes it ideal for this application to cope with the update rate.
Bob
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It's been around for quite a while. FLASH and EEPROM are mostly useless for this type of application. Given it's an electric meter they could just use low power SRAM with a super cap backup supply.
MBQ
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Man at B&Q wrote:

Too easily corrupted. Fe RAM has indefinite data retention after removal of power, better than 10^^15 write cycles, and a glitch during writing won't corrupt the rest of the data (According to the makers...)
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John.

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wrote:

Easily designed around.

You would struggle to "corrupt the rest of the data" with any technology.
MBQ
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Man at B&Q wrote:

To use one example meter I know of, in what was an empty shop for three years, how would your idea cope with a couple of years of disconnection?

I must remember to tell the makers of my cameras that. They tell me under no circumstances must I take the batteries out while it's writing to the card, as that may render the card useless.
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wrote:

OK, so go back to using FRAM.

My point stands.
The warning, "may", is due to potential corruption of the card's file system that isn't designed to be robust enough to withstand corruption of a single critical memory location. The data is still there if you have the right tools to recover it.
MBQ
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Man at B&Q wrote:

Not always, IME, but you may have been luckier. Luckily, the camera with a problem was one used by a member of a group, so they just swapped pictures.
--
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John.

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FAT filesystems can't be made safe in this way because they require multiple sector updates to be made simultenously, to remain self consistent. They have a common delayed action corruption mode where you can read all the data OK after an interrupted operation, but latent inconsistent spacemap update results in data corruption sometime later on when the filesystem is written to again. Also, because there are so many different implementations of FAT filesystem drivers which do things in different orders and may not use the clean shutdown bit, it's not easy to spot this without doing something like a full chkdisk operation, which appliance devices usually don't implement, nor have the time to do.
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Andrew Gabriel
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On Tue, 17 May 2011 12:55:31 +0000, Andrew Gabriel wrote:

Can you explain? If they are built with one FAT, I can't see why that would be so, although there might be some free block loss.
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You never worked with bubble memory did you?
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It was actively worked on where I used to work, but not personally, no.
I was thinking of more modern, mainstream, technologies, not dead ends.
MBQ
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It had some interesting faults. I killed the development of bubble memory cards on SystemX by designing something far better to replace them. Cheaper, more reliable and five times as fast tends to kill the competition rather well. Its still in use now and its more than a decade (or two) old.
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[sorry for incorrect threading and I hope I got the original attribution correct, I've only got half the thread visible]
Andy Dingley wrote:

Build your own 32bit core store for an arduino
http://www.corememoryshield.com/report.html
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On Sun, 15 May 2011 08:57:08 +0100, Andy Burns wrote:

Yup, saw that on sparetimegizmos recently. I do actually have a piece of antique core - 512m bytes from an Atlas machine!
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Bob Eager wrote:

If you fancy 'knitting' some more £25 for 45,000 ferrite rings
http://cgi.ebay.com/300556183278
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On Sun, 15 May 2011 10:28:48 +0100, Andy Burns wrote:

That would be bad enough if I had two eyes! As it is....
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