Swede Posted June 18, 2008 Posted June 18, 2008 I though about posting this is the supplier review section, but it is more of a general observation about digital scales, cheap vs expensive, and what you can get for very little money. I started my adult life as a chemist, though I am no longer practicing outside of this hobby. I have always been a sucker for lab equipment. My manual balances have been gathering dust since modern digitals have appeared at such low prices. I've gathered several of them over the last couple of years: http://www.5bears.com/firew/scale01.jpg The best is the VMC VB-302, 500g X 0.01g. At maybe $175, this is considered a low-end instrument for real lab work, but it has a nicely sized platter and a good range. For more casual use, I've purchased three of the pocket scales, a Jennings on the left (total POS), the one in the middle (1,000g X 0.1g) and the Digiweigh, on the right. http://www.5bears.com/firew/scale02.jpg This little scale has a very limited range of 100g X 0.01g. The problem with cheaper scales is poor sensitivity more than it is accuracy. If a scale can resolve to 0.01g, then I WANT it to sense the addition of minute amounts of material. Often they don't. You flick a few grains into the cup, then have to gently touch the cup to trigger a re-evaluation of the mass. It's annoying. Even the VMC does that. Recently I have been doing a lot of small-scale, repetitive measurements, and I put the digi-weigh to work. I was amazed at how good it was. The controls are excellent, and for a pocket scale, the platter (stainless) is huge. Best of all, it had superior sensitivity to the VMC scale that was 10X the cost, even though both resolve to 0.01g. I am consistently able to add 0.01 gram portions, and the scale senses it easily, no more touching the load. Of all the pocket scales I've tried, this one is by far the best. http://www.5bears.com/firew/scale03.jpg How does it do this? My theory, since it maxes out at only 100 grams, it has a better innate ability to sense minute changes of mass vs the 500 gram capacity VMC. The model is the Digiweigh DW-100AS, and can be found on eBay... here's one. DW-100AS on eBay, $17 buy-it-now I have zero association with these people, it's just a great scale. Maybe other scales that are 100g X 0.01 do about the same; I don't know. But for experimenting or perfecting compositions, it's perfect. I hope this helps someone. As cheap as these scales are, it's good to have one that can do a kilo, and a second one for finer research work. Mods, if you feel this belongs somewhere else, please move it!
tentacles Posted June 18, 2008 Posted June 18, 2008 Swede: I have the 600x.1g version of that same scale and it works pretty well. It doesn't always like to sense minute additions but a little tap will settle it out. It seems to be sold under a lot of brand names, mine is "american weigh". I really want a .01g scale for chemistry.
TheSidewinder Posted June 19, 2008 Posted June 19, 2008 Back when I was flush with money, I purchased 3 very good ones. An Ohaus CS-200 - 200g x .01g, an A&D SK-1000 - 1000g x .5g, and an Ohaus EB-30 - 30kg x 1 g. All are multi-scale: grams and ounces/pounds. None of them were cheap (and all are in pristine condition). I considered it money well-spent at the time, but if I had to do it over again, and knowing what I know now, I'd pass on the A&D and go right to the big Ohaus. P.S. The A&D is for sale if someone wants a damn good mid-range scale, but has a 1kg calibration weight (actual weight 1000.030g) and Power Supply included so it's not cheap. $200 plus shipping.
psyco_1322 Posted June 19, 2008 Posted June 19, 2008 Thanks for the great info Swede, I keep these in mind if I decide to get a new scale. For now Im sticking with my triple beam balance. Atleast it knows when you add small amounts unlike some digitals. I had a scale like this one given to me by a friend:http://www.southwestscales.com/Ohaus_Triple_Beam_720-S0.jpg If I need to get precise but not accurate I just get out my 500 grain powder scale that is single beam.
Swede Posted June 19, 2008 Author Posted June 19, 2008 psyco, I grew up with the classic triple beam, and another variant that had a dial for the fine tuning, and that dial job was especially nice. I wish I knew how it worked... I'm guessing you are "winding" some sort of calibrated torsional spring. However it worked, it was cool. I think the dial range was 10 grams, with a vernier. You'd set the weights to the desired mass, minus 10 grams, and dial to zero. Add chems till the balance tipped, then simply began to work the dial, adding more chems, etc. I found a pic of a simple one, the "Dial-o-gram": http://www.sks-bottle.com/340c/images/Scales7.jpg Check it out, the website with this balance has some containers and such useful for pyro and chemistry: http://www.sks-bottle.com/ In our lab, there were also mechanical cabinet balances that had unbelievably intricate clockwork inside, with super-precise beams and masses that were hidden in the cabinet, away from dust and draft. What you saw as a user was a mechanical dial, somewhat like an old-fashined shortwave radio set face. Those must have been unbelievably expensive in their day, and are now mostly replaced with load cells. But I'll bet for the finest precision work, the purely mechanical balances still are much used. I do agree, beam balances are excellent units, but I've just gotten spoiled and lazy with the digitals. I'm tempted to pick up one of those Dial-o-gram balances though. Tentacles, where this scale really shined was with the polyurethane glue experiments. I was working with dozens of 10 gram batches, very repetitive work, and the 0.01g res was both needed and useful. As I mentioned, I was pretty surprised to see this scale had better sensitivity than the VMC, although I will say the VMC is more accurate over a larger range, and settles better. The large platter is a big bonus. Too many pocket scales have midget platters.
flying fish Posted June 20, 2008 Posted June 20, 2008 I've been floating along with my cheap pocket scales from brands like digiweigh and those work well but seem to eventually break (to be fair, I don't treat them that nicely either). Recently I got a nicer pocket scale (my parents got it for me for my birthday). At least, I'm pretty sure it is nicer. It is an "ameriweigh" scalemate .01 x 200. It definetely looks better made, with a more smooth fit and finish, sturdier looking platform, and thick magnetic cover rather than a cheap click-on one that looks like it is made out of the same quality plastic as petre dishes! Now I'm considering buying a mechanical scale (triple beam) as I'm guessing it is less likely to break...No electronics, no piezoelectric components or sensors...just some weights and other simple mechanical components. Am I correct in my assumption? Then again, I could probably get 5 or more pocket scales for the price of a good mechanical balance these days...
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