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Posted by Jim Yanik on June 5, 2006, 10:09 am
cornytheclown@hotmail.com wrote in
>
> Jim Yanik wrote:
>> searco@theinventions.com wrote in
>>
>> >
>> > Jim Yanik wrote:
>> >> I bought one of those 2.99 HF digital multimeters(item 90899) that
>> >> were offered during their sidewalk sale,and the meter read several
>> >> 1.5v batteries as 1.8-1.9 volts,far out of spec(1%,+/- 2 counts).I
>> >> returned it,no questions asked,and the 2nd meter reads properly.
>> >>
>> >> It is not a serviceable meter,either.It's chip-on-board
>> >> construction,and there were several solder splashes across tracks
>> >> on the inside. Strictly throwaway.
>> >>
>> >> Well,whadda ya expect for 3 bucks... ;-)
>> >>
>> >> --
>> >> Jim Yanik
>> >> jyanik
>> >> at
>> >> kua.net
>> >
>> > DO NOT use this cheap meter to read high voltage circuits. Cheap
>> > meters can potentially blow up in your hand if you try high
>> > voltage. I've had this happen.
>>
>> One blew up in your hand? On what range/voltage?
>> How badly was your hand injured?
>>
>> > Get a good meter for anything more than
>> > batteries. It is well worth the investment.
>> >
>> >
>>
>> The manual says to not measure voltages above the range ratings.
>> RTFM.
>>
>> What do you consider "high voltage"?
>>
>> --
>> Jim Yanik
>> jyanik
>> at
>> kua.net
>
> whats the meter rated for ???.... around the house it probably wouldnt
> be bad or for some sort of residential work....but for the most part
> these el cheapos...are used around the house and for that they are
> fine.
>
> Most meters I own are good for 1000 volts at least...but I have one
> really really nice hioki that got from some slob off ebay for 25.00
> thats only rated at 300 volts....dont know why it has this
> rating...its a very upper end meter ..original owner didnt know what
> he was selling..~:>....just made for use outside the USA...
> I use it around the house and for general electronics work....
>
> Ive never had a meter blow up in my hands....I used to use an old
> radio shack digital to measure current on high voltage
> transformers....15 kilovolt...7800 kilovolt......It held up for
> years......finally "blew it" when I put too many amps thru it....but
> all I heard was a pop..got the fuse AND the electronics... Just the
> meter and regular leads though...everything layed out on plastic
> sheeting though...leads seperated etc...
When your fuse opened(opening the current shunt),then the entire voltage
was across the DMM;that's why it failed.
>
I doubt the HF meter case is insulated for much over 1 KV.
The meter leads are not either,I suspect.
One thing I did not like about the HF meter when I opened it up was the
resistor voltage divider,just several discrete resistors too closely
spaced,and mounted vertically with the top wire looped back to the PCB.
That could cause problems for measuring higher voltages-too close a lead
spacing may allow leakage.
The 9V battery supplied was a "heavy duty" zinc-carbon type,not very long-
life,and more prone to leakage than alkalines(except for Duracell).
--
Jim Yanik
jyanik
at
kua.net
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