Has anyone used one of the Chinese digital lab scales? I'm in the process of making weights for my Rockwell Superficial Hardness tester and need a scale to fine tune the finished weights. I'm only going to use the scale this once and will likely never need it again. There's a couple of scales available on eBay/Amazon/Walmart that appear to have the weight capacity and precision required. Specifically I'm looking at the Ktaxon B30002T which has a listed capacity of 3000g and precision of 0.01g. Feedback on this scale or recommendations are welcome.
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Digital Lab Scale Recommendations?
- Thread starter Dave G.
- Start date
- Replies 5
- Views 1,971
WHHJR
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- Jun 5, 2009
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- Near:Louisville, KY
I am no longer current on scales but IIRC we expected one part in 19999 Readable signal on load cells (ie 4 and 1/2 digits).
2¢
2¢
WHHJR
Stainless
- Joined
- Jun 5, 2009
- Location
- Near:Louisville, KY
And don't forget that the minimum reading (.0xxx or whatever)isn't accuracy. Accuracy linearity and repeatability are separate concepts.
I recently bought a small 0-100 Gram scale which has a minimum reading of 0.01gm. When i checked it with test weights It generally was within 0.01gm. I was amazed....
I recently bought a small 0-100 Gram scale which has a minimum reading of 0.01gm. When i checked it with test weights It generally was within 0.01gm. I was amazed....
I have three electronic scales that together cover the range of masses I need to measure. I also have NIST-traceable calibration weights for each. The 'linearity' calibration procedure for these scales requires weights at or near either end of the range (e.g. 0 grams, no weight, and 200 grams for a 200 g scale) plus a weight in the middle (100 g for this example).
Without your own calibration weights that weren't supplied by the manufacturer of the scale you have no idea the actual accuracy. This is no different than for a, say, micrometer. All you know with a micrometer is 0 is 0, because you adjusted the spindle to make it so. If you also have a calibrated 1" gauge block you now know it is correct at 0 and 1" (assuming it is), but you don't know about the accuracy in between. That's why micrometer calibration checking sets contain several blocks, to test the micrometer mid-range and at several orientations of the spindle. If a micrometer passes all those tests it's still possible it could be off at some other point in the travel, but the odds are small.
With an unknown electronic scale, irrespective of how many digits the readout has, you won't have any idea of its accuracy without at least two weights calibrated by someone other than the scale's manufacturer.
I have a weight set from my standard hardness tester that I am going to use as "calibration weights" to make sure the scale was accurate. The weights I'm making will be made light(under weight) and trimmed to spec with lead shot in a covered pocket. The weights will be 600g and the standard tester has one weight which is 2000g and a second that is 2400g. Not ideal for linearity testing as both are on the upper end of the scale. I will need to look-up the calibration procedure for a hardness tester and see what the tolerance is for the load - then I can calc just how precise and accurate my scale needs to be. But, shooting from the hip I'll guess that +/- 1g will be close enough. The load can be adjusted internally as long as your weights are in range. I have calibration blocks for the hardness tester, so I can verify the the readings before making measurements. This is for personal use and not certified results (so I can be a little fast and loose). Finally, yes I know about accuracy and precision. See my favorite pic explaining the difference below:
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