I have measured with a digital voltmeter the mains voltage at home in Spain and got 295 V AC. At the beginning I get a reading of 240V and then it quickly goes up until it stabilises at 295 V.
Is this reading correct?
The AC here is triphasic.
A couple of IC boards for motorized doors, permanently connected to the mains, have recently failed. Perhaps it is related.
I will ask the electricity company as well
asalcedo wibbled on Saturday 03 October 2009 14:41
Are you using a true RMS meter? What happens if you measure it across a load, eg a kettle? Are lights burning extremely bright? Are you fairly confident that your meter is working correctly?[1]
You mean 3 phase? If so, that's the same as the UK. One possibility is your meter is reading it wrong if, for some reason, you are not getting a decent sine wave (unlikely I would have . The other reason is your voltage is genuinely dangerously high.
Phone them straight away on their emergency number. It's quite possible there's a neutral fault which can give either a very high L-N voltage, or a very low one depending on which of the 3 phases you are on.
Anyway, they ought to take your report seriously enough to send a bloke round to check. As it could be an indicator of a serious network fault, I'd expect them to turn up pretty quickly.
[1] The electricity company might ask you why you think your voltage is high.
What do you mean "at the beginning"? do you mean at the instant you connect the meter? I would expect a DVM to stabilise almost immediately, and would regard the reading as suspect. Can you try your meter on another supply, or try another meter on yours? Is the battery in the meter good?
On Sat, 3 Oct 2009 23:01:07 +0100, "Graham." had this to say:
I certainly wouldn't use a digital meter for this type of measurement. You'd be much better off using a traditional Avo or similar, preferably with a fairly low ohms/volt characteristic, to try to avoid silly readings due to induced voltages and the like.
I couldn't agree more.
Dave
Hardly worth buying a traditional AVO if you already have a DVM. Just measure across a load. Anything will do. Take the top off an appliance plug or a lamp holder (both must be switched on and working) and measure there.
But I'm not quite sure how you'd get a higher than actual mains voltage with a high impedance meter? You can get strange readings on an circuit that is switched off due to coupling of some sort - but not higher than the mains voltage?
On Sun, 04 Oct 2009 00:05:28 +0100, "Dave Plowman (News)" had this to say:
Horses for courses, innit. I have two or three digital meters (including a Fluke 73) (I can't find it at the moment!) and a couple of analogue ones. I really prefer the analogue meters, although the Fluke is occasionally useful if just tapping out conductors because of its continuity beeper :-)
To check mains voltages of uncertain waveform/harmonic content it would be better to contact a friend who does have an analogue (and trusted) meter.
Ferranti effect? (I'm not being totally serious).
Ah, that's because it isn't in a Marconi cage! :-)
i was similarly baffled measuring old car batteries
- it was a dud battery in the multimeter.
[g]
How can you not measure the mains across a load? Ask everyone in the street to turn everything off?
Bill
Its been shown time and again that you can 'see' an analogue meter faster than you can 'read' a digital one, as well.
A digital readout is inferior in every respect eccept precision. And cost I suppose. Cheap as chips.;-)
You can't do much electronics stuff then - because the loading of an mechanical meter gives false readings.
Or measure under load as I said. You can make up a dummy one for a DVM to replicate a mechanical one if you wish.
On Sun, 04 Oct 2009 09:57:14 +0100, "Dave Plowman (News)" had this to say:
I use a digital meter (usually) for electronic work :-)
only on high impedance sources. I often preferred analogue for electronics, and I did no shortage of electronics. Quicker readings, much easier to work with when you need to watch what youre probing the whole time (high voltages in awkward places, thanks to historic designers), the fact that they can read well above fsd (by speed of pointer movement), and digitals are a non-starter for non-steady voltages.
The last generation of analogues had fet opamp input stages, same high input impedance as digitals.
NT
Better DVMs have a second scale that sort of mirrors what a mechanical one does. And have average max and minimum hold.
I have a Heathkit valve voltmeter which does much the same. Long before FETs were invented.
One beauty of a mechanical meter is it only needs batteries for resistance measurement. Stick an FET on the front and you lose this.
Nor unless its working on very low current circuitry. On any case you use a scope, not a DVM by and large.
The load is the source impedance of the supply. Less than a few ohms generally.
Urgh - the enfoced beeper drives me nuts on the lowest range. Handy to have for continuity test, and a pain in the backside when tracing out lots of low-resistance things. I keep meaning to take mine apart and add a shut-off switch for the beeper...
JOOI, does anyone market a meter where the test leads *don't* have a "tangle yourselfs up when nobody's looking" feature? :-)
A scope for measuring voltage? Ok for a quick guide, I suppose.
A load is applied to a source in my world.
In yours it would make f all what type of meter is used.
In message , Frank Erskine writes
Having just had this annoyance and had to go and get the Avo why don't DVMs just a "push to load" button that sticks 10k ohm or 100k ohm across probes?
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