my concern is what happens when you connect real AC mains (that is 230v, not that paltry 110v) to any of the cheaper multimeters.
I'd say the only reason they rate it for mains AC is that the lowest applicable rating includes voltage surges of 2500V+ which would be too much for it. Measuring 230V AC though? Probably OK, although I wouldn't advise anybody to do it - surges happen!
not quite sure what you've written is entirely clear, but i
think you're asserting that for measuring 230v AC the meter should have a 2.5kv surge rating. with this, i would broadly agree. there are many standards from around the world, but i would agree that being able to withstand a 2.5kv surge is a reasonable compromise for measuring domestic AC.
but are you
also saying that it is OK for a piece of test equipment with a scale calibrated up to 250v or more, sold as being suitable for the purchaser to measure domestic AC mains, to
not be able to withstand a 2.5kv surge? if this is what you are saying, then, well, why do we even bother having these safety standards?!
i think we
all agree that DT-830 style multimeters are not
suitable for measuring domestic AC mains voltages. i am just going one step further to suggest that manufacturers and retailers of such multimeters should be held accountable for selling a product that does not comply with the relevant safety standards. ie, farnell should not sell such products, repco and bunnings (or walmart or ASDA) should not sell such products, ebay should not allow such products to be listed on their site.
as an alternative, it should be fine for anyone to sell products that either
comply with the relevant safety standards (the Fluke 101 provides a good example), or that are
constrained to be usable only within safe limits - that is <50v RMS or thereabouts. either step would not seriously impact the manufacturing cost: remove the 500/1000/2kv ranges, limit the display of 200v ranges so that the multimeter displays an 'over-range' for anything over 72v AC/DC, move current ranges to a separate uA/mA input socket, redesign PCB layout and component choices to meet minimum creepage and clearance distances.
after all, if i were to set up shop selling pairs of rubber kitchen gloves marked in big letters across each glove as "250v safe", how long would i be allowed to stay in business?
PS: Can you put your hand on your heart and swear you always wear gloves, etc. when poking at mains AC with your Fluke?
i take reasonable precautions around mains AC voltages. if i have any doubts about what i am doing, i STOP. that is simple
common sense, coincidentally one of the
least common commodities in this universe.
cheers,
rob :-)