Posted by Sherman in Idaho [72.47.153.112] on Sunday, February 02, 2014 at 22:56:01 :
In Reply to: Re: Cheapo multimeter advice and warnings posted by derek [68.124.70.47] on Sunday, February 02, 2014 at 22:01:43 :
There are a lot of Fluke meters on ebay. The older models are just fine, maybe even better than, the new ones. I wouldn't go back to anything older than a 77, though. The original series (the 8020 style units, with Norm Strong's chip in them which Intersil pirated as the 7106) have problems with the seal on the LCD. They tend to turn black from the edges in, which ruins the unit even if all the electronics are fine. But there are so many newer ones on ebay for $20-$50, that there's no need to mess with those old ones. I can't speak to the newer (Danaher) generation of Fluke meters since I don't have any.
The faults with cheap meters are very sneaky ones. They're not what a person would expect. It's not like a cheap micrometer or calipers might not be as accurate or stable as a good one. We all know we don't need great accuracy for automotive work, although being off by 2-1/2% really surprised me. The problem is all the other ways they cut corners to make them cheap. Fusing on the current ranges is minimal to non-existent, which means if you accidentally leave the leads in the current position and hook them across a powerful voltage source, there's going to be some fireworks. I don't know if they still do it on their small meters, but fluke used to include both a 2A 250V and a 3A 600V fuse, in series, on the current ranges just to be sure. The cheap meters have no filtering on the input, so if your source is noisy (a mechanical voltage regulator, for example), the meter reading will go nuts. Some completely reset themselves and some just flash random garbage. And then there's the problem of a low battery causing the meter to read seriously high, while otherwise appearing to work just fine. I've also noticed that in a damp environment (tool box in the back of the truck, or unheated shed, for example), the cheapies give erroneous readings, but then work again when dried out. This is probably because they're soldered with "no-clean" flux, which leaves a moisture-absorbent conductive residue on the board.
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