> > From: John Sessoms <[EMAIL PROTECTED]> > Date: 2007/06/21 Thu PM 04:09:51 GMT > To: pdml@pdml.net, pdml@pdml.net > Subject: Re: Power - was Re: Lightroom and organizing files > > > > > From: > > mike wilson > > From: John Sessoms <[EMAIL PROTECTED]> > > > > > > > > The local power company has gone to some kind of digital metering system > > > and has a data pulse impressed on the AC cycle. I've had problems with a > > > couple of cheapo fluorescent fixtures where you could actually see the > > > lights pulse off every 20 seconds. You could actually see it on a > > > digital voltmeter as well, but not on the power output side from the UPS. > > > > > > That would be illegal in the UK. There are very strict requirements laid > > down as to what voltage and cycles (within very small limits, usually > > required to be corrected to absolute values over a 24hour cycle) have to be > > delivered. AFAIR, deviation from a plain sine wave is also not allowed. > Then they'll probably will use a different scheme for programming and > polling electronic power meters over there. It's gonna happen, 'cause > they're all lookin' to cut expenses and increase profits. Remote reading > power meters means you can lay-off a whole lot of meter readers. > > I think they originally introduced this around here back in the 80s as > part of an energy conservation measure. They had this scheme where they > would offer a discount rate if you'd let them come in and attach a > control to your hot water heater so they could turn it off during the > day when they were approaching peak loads. The idea was to reduce the > requirement for additional capacity by damping out the peak with load > shedding. > > The data pulse is how they told the water heater controls to switch on > and off. > > I use natural gas for hot water, so it didn't do me any good. > > About 95% of the people I've told about this can't see the lights blink, > but enough can that I know I'm not crazy ... at least not that way.
I think the original reason for the UK legislation was to protect power-critical places like hospitals and scientific institutions, so that they could maintain accuracy of instruments. I suppose the introduction of transistorised, regulating power supplies, needed for the less stable parts of the world, has overtaken that specification. ----------------------------------------- Email sent from www.virginmedia.com/email Virus-checked using McAfee(R) Software and scanned for spam -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
