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Just bought a cheap n nasty DMM today while looking through my local maplins store, and must say quite impressed for £29.99

Its a basic meter but has an RS232 interface so you can hook it up to your PC.

heres a graph of voltage supplying my house for just under 3 hours 6:20PM to 9:15 (ish)



i was running around the house turning on and off shower/cooker/ oven etc

The graph shown was done on Excel, but the software that comes with the meter shows a scrolling graph and the cool thing is that i can tell when the kettle has boiled , using another PC to view the data.

Am now doing a 24 hour graph, so will post back tomorrow night if the PC does`nt crash.


[This message has been edited by sanUK (edited 04-11-2004).]

Sandy,
What on earth happened at 20:42Hrs?.
Thats a big sag in line voltage!.

Sorry to post a second time but, a great majority of our time as Electricians over here in New Zealand, is spent doing Power Quality measurements.
Whether it be Voltage/Current or Maximum Demand metering.
What we look to do for our customers, is to minimise thier kVA supplied vs kVA used.
Coming from a PoCo background, this is the biggest thing.
Power Factor is the biggest killing factor Of Industrial Power systems.
If your Plant has an over-all PF of 0.75 lagging, you are under using your conductors by 25%.
Motors are the biggest killers of power factor, having a reactive component to thier current.
I would look to correct to 0.95 or Unity.

Quite a dramatic looking blip there at 8:45-ish, but even at the lowest point still 237-point-something volts.

Voltage regulation in the U.K. is generally pretty good.

(Psst.... Isn't it nice to know that officially our nominal voltage is now 230V? )

your idle voltage is 245V?? thats really quite high imho.
Our idle is about 235V (237 at night).

What did you kick on at 20:44?

sorry for the delay in replying been a busy day.

Firstly what happened at 20:42 i dont know i was out (honest guv ) could have been neighbour/s on the same phase ??

FYI House is a basic PME single phase supply, 100A fuse, housing estate lots of bungalows.

Here as promised is a 24 hour graph (nearly 24Hrs )



Due to the graph above being compressed HERE are the results in EXCEL format if you want to do your own expanded graph.


Andy - yep idle usually around 244.5v, i compared the cheap meter with my main one (Seward Combi-Compac) and its pretty well much bang on.

Trumpy - as for power quality measurements, i was speaking to a local Amusement arcade owner a few months back when i went to repair some kiddy rides, and he was telling me that he had got onto the Electricity board a few years ago because his bandits/fruit machines were continually breaking down, they fitted a graph recorder to check voltage for a few days and the guy did say the voltage at peak times was too low. As i said this happened a good few years ago and the owner didnt go on to say what happened, but i recon the mains cable would have been upgraded, because he still has got a lot of old machines still running.

Anyway im happy with my new meter, and wont bore you all with more graphs.

Is this the period from Saturday day to Sunday evening?

The slight dips around 8 a.m., 1 p.m., and 6 p.m. are pretty much expected. The step-up around 1 a.m. is interesting. If the voltage suddenly sagged around that time, I would put it down to all the Economy 7 loads coming on, but the step-up suggests maybe a PoCo switching operation.

Nobody around here will get bored looking at this stuff!

Andy,
The 245V-ish idle isn't that high. Don't forget that although we're officially 230V now in the U.K., for all practical purposes our supplies are still really 240V (hence my comment above). So the 245V idle voltage in the graph is only about 2% above nominal.

No data logging connected here, I'm afraid, but for what it's worth I'm reading 239.6V at 11 a.m. Tuesday.

Guys, would anyone share his excel logging program for testing purpuroses.
I have one that doesn't support writing a file, the biggest longtime i can have as a diagram is 2 minutes.
i have a conrad / voltcraft VC820 with optical RS232 interface. Perhaps this one works with any other software.

The idle voltage around by area is pretty worrying, it is usually around 250v.

But i've saw this rise to 256v on one occasion.

That is slightly over the permissible upper limit, either the current 230V +10% (253V) or the old 240V +6% specification (254.4V).

{Edited for typo}


[This message has been edited by pauluk (edited 04-16-2004).]