That makes sense, for the reasons I just mentioned, and I certainly have one in my toolbox. However, for domestic work when a circuit has been 'isolated' just by interrupting the line conductor with a SP MCB, a lamp cannot be used for a N-E check if the circuit is RCD protected - presumably not an issue for DNO work.
Ah - there are (or were) clearly 'Drummond Lamps' and 'Drummond Lamps'! Mine has a 15W 250V incandescent lamp/bulb (like this) - i.e. 60mA at 250V.
No cable is double insulated. They are insulated and sheathed, with the sheath providing mechanical protection. (It is not rated for its insulation properties.)
I don't think you need to restrict that to "standard" digital multimeters. I can't see how any sort of digital meter could function without a battery of some sort (or a mains supply, if it were a bench instrument) - something has to power the electronics and display!
AFAIAA, the same is true of most/all of the "two pole testers" advocated for 'testing for dead', isn't it? - again, if they have any electronics or a display they must have a power source (other thgan the voltage being measured). Only truly passive (moving coil or moving iron etc.) analogue meters could measure voltage without a battery (or mains supply) - and only us oldies are likely to have one of thoseLamps (or LED equivalents) are another passive option, but they don't give a 'measurement' (LED ones may give a vague idea of voltage range).
Kind Regards, John
That's reassuring to know.
I'm a lot more of an oldie than you, which is probably why I still have a goodly collection of (mainly still working) moving-coil analogue multimeters, including a couple of AVO Multiminors, which I still use. I also have a 'wind-up' real Megger somewhere, too!
You tell us! I presumed that you must have been thinking of an 'old-fashioned' moving-coil multimeter, whose battery is only required for resistance measurement.
I don't think you need to restrict that to "standard" digital multimeters. I can't see how any sort of digital meter could function without a battery of some sort (or a mains supply, if it were a bench instrument) - something has to power the electronics and display!
AFAIAA, the same is true of most/all of the "two pole testers" advocated for 'testing for dead', isn't it? - again, if they have any electronics or a display they must have a power source (other thgan the voltage being measured). Only truly passive (moving coil or moving iron etc.) analogue meters could measure voltage without a battery (or mains supply) - and only us oldies are likely to have one of those
Kind Regards, John
Yes, although my Fluke T110 two pole voltage/continuity tester (and all the current Txxx range) has a secondary passive indicator in addition to the bargraph (LCD on the more expensive ones) and will still indicate the presence of a voltage >50v AC, although admittedly not measure it's value, with the batteries removed.
I'm not sure if I count as an oldie (still under 40) but I do have a working AVO 8 analogue meter in the shed!
It's reassuring to hear that most of these 'voltage testers' do work, to at least some extent, in the absence of batteries. However, I would remind you all that discussion was started by a comment about multimeters - and there is no way that a a digital hand-held multimeter can measure/display anything in the absence of batteries (unless it has a built in 'passive' voltage detection display - but I can't recall ever having seen one which does).
Indeed - and I'm still known to do that sometimes! It's really only the RCD issue which detracts a bit from their general usefulness.
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