XPost: sci.electronics.equipment   
   From: presence@MUNGEpanix.com   
      
   In sci.electronics.equipment Ralph Mowery  wrote:   
   > In article , presence@MUNGEpanix.com   
   > says...   
   >>   
   >> > So should I assume the cheaper ones are lying?  Or have they just made a   
   rough estimate adding the two errors?   
   >>   
   >> might be both. I dug out my first DMM, a Wavetek DM2, circa 1990s. It might   
   >> have been from a raffle or something like that.   
   >>   
   >> The DC voltage specs range from 0.8% +1 digit (not bad really)  over to the   
   >> AC ranges which are "1.2% RDG +10 Digits". If I had new leads, I'd trust it   
   >> with outlet voltage, but would stay away from 208volts. The meter has 3.5   
   >> digits or max display of 1999. I'm figuring a real 100volt AC reading could   
   >> be 99 to 101 plus another error of +/- 1 volt for the 10 digits tolerance   
   >> on the display or count. so 100volts from your Japanese outlet reference   
   >> might read 98 to 102 volts. So while in the ballpark, it's better than you   
   >> can read off a Simpson 260 meter in the AC voltage range. I could be wrong   
   >> on this too.   
   >>   
   >> It's a pretty decent meter for poking at DC circuits for the tens of   
   >> dollars is must have cost when new.   
   >>   
   >>   
   >   
   > It seems that maybe due to modern manufactoring the meters are more   
   > accurate than they were 20 years ago.  I bought some DC voltmeters from   
   > China.  They display 3 digits.  They read from 0 to 99.9 volts.  I coulg   
   > get 4 of them for less than $ 15 including the shipping.  I hooked all 4   
   > of them in parallel with a Fluke 87 .  Three of them tracked right along   
   > with the Fluke with the last digit sometimes being one high or low from   
   > 0 to 24 volts.  The fourth one was off by an average of 2 on the last   
   > digit.  I found an adjustment screw on the back of the meter and tweaked   
   > it and re ran the test.  It then fell in line with the other meters.   
      
   Have you run this test with AC? That seems to be where the wheels come   
   off. I brought up this thread to a friend and he mentioned his quest to   
   repair some sort of HP true RMS meter that uses a thermocouple and heater   
   to properly measure complex waveforms. I can't even guess how slow such a   
   meter might be.   
      
   > I had 3 or 4 of the Harbor Freight 'free' multimeters.  The ones that   
   > usually sell for around $ 5.  They seem to be reasonable accurate for   
   > the money.  Plenty accurate for the home user to test things around the   
   > house.  I do admit that the safety issue of putting them across the 120   
   > or 240 volt power wires is somewhat doubtful.  I sure would not use one   
   > where I worked to put across the 480 volt 3 phase system that is  fused   
   > with 200 amps.   
      
   I'm pretty timid with anything upstream from a plain outlet. I had an   
   edison base fuse burst in my hand once. Never seen one come apart before.   
   It was just a 120v lighting circuit, but right off the service panel.   
   There's way more excitement near those things.   
      
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