I have a 7kg scale bought off ebay. It's not the cheapest, but it is accurate. Imho going cheap for things like this just means you don't get repeatable accurate results.
A quick search pulled up the exact scale I use. It's only goes to the gram though, but that's good enough for me, and it weighs any bike parts pretty accurately.
http://www.ebay.com/itm/My-weigh-7000g- ... 3a6da6b7d2" onclick="window.open(this.href);return false;
Note however, I never use the top bowl, it zeros when I turn it on, and it's been dead on accurate for quite a few years.
Best way to test if your scale is accurate, google for info on coins from where you live, take out a bunch from your wallet, make sure they aren't super old and worn or dirty, and weigh them. Then compare them to the official weights.
Found this page for aussie coins including weight discrepancies between different years of currency (check the dates on the coins)
http://www.decimalcoins.com/" onclick="window.open(this.href);return false;
Just now I did a 2 coin test with the aussie $2 and 10 cent piece, which should weigh 6.6 and 5.66, 12.26 total. Scale reads 12g
$2 goes straight to 6g by itself, and 10c goes to 5g, then a second later goes to 6g (rounds up).
Also has been accurate on common bike parts like say a dura ace octalink bottom bracket, which has been tested and reported to be 173/174/175 grams by other people. My scale read 174 when it was weighed before put into a bike.
Here's the official site, including video of them using a different myweigh scale on mythbusters
http://www.myweigh.com/index.html" onclick="window.open(this.href);return false;
Cheers,
Ian
