Precise, but not precise enough. Some design flaws.
Kanada’da 15 Mart 2018 tarihinde değerlendirildi
You get what you pay for. I've taken university courses that involved quantitative analysis in chemistry. With research grade scales that measure down to the 0.001 gram, there are significant differences in those scales compared to cheap versions you buy online.
In laboratory-grade scales used for research, yes, even the air currents caused by the heating system can cause fluctuations in the measurements. Measurements would flutter. This is why they are designed with a tall glass box to block out air currents, and the sliding door would need to be closed. These scales tend to be about $1000 or more. Even the laboratory bench needs to be perfectly level, and the scale itself would have 4 adjustable legs to balance the scale. If the scale itself is not level, the measurements would be off. Furthermore, from experience, even fingerprints result in measurement differences. That is how sensitive those scales are. And if liquids are being measured, the glass stopper on the flask must be on, otherwise the slight evapouration will result in a gradually declining weight measurement.
In contrast, this scale is no way as precise. One thing I DID find was that even for the same object but placed on different surfaces, the measurement would be different. This might be due to very slight inclines on the table surface vs counter top, as both are not 100% level. When the scale is not on a perfectly level surface, it is not moving perfectly up and down, and slight friction within the measuring system itself is affected. The difference I am seeing is it might weight 10.006g when the scale is placed on the table, but 10.011g when placed on the counter top. These subtle differences likely due to how level the table is, can affect measurements by +/- 0.005g or so.
There does appear to have some problems with the scale. Some degree of friction is involved. If I have nothing on the scale, pull the scale upwards first and releasing back to resting position, and it is reading 0.000g, and then I place the 10g weight on it, it might give me 10.028g. But if I start with 0.000g, put the 10g weight on it, depress it all the way such that the scale reads 0-Ld (essentially maxed out the scale), and then allow it to spring back up, it would read 10.000g. This means that depending on if you first fully depress the scale, or if you fully stretch the scale surface, and then start a measurement from there, the slight friction or spring property difference causes a variance of +/- 0.028g.
Also the two weights are slightly different. one might be 10.000g and the other might be 9.997g. I don't know how accurate these weights are.
One of the biggest problems with this scale is the lid itself. It acts on the hinge on the back, and it is possible to lift the lid about 45 degrees or more and the friction would hold the lid up. Unfortunately, I believe that when the lid is lifted up, it is exerting some strain onto the base itself. The distortion on this is enough to change the scale reading from 0.000g to 0.016g. So there is a design flaw with the lid where the tension affects the readings. +/- 0.016 g.
If everything was kept the same and stable (and measuring with the lid always closed), the same item might vary by +/- 0.001g.
So when you combine all of the variences mentioned above, when not properly controlled, the same item might have a total variance of 0.005g, 0.028g, 0.016g, 0.001g for a total of +/-0.050g if everything happened to line up that way. (realistically, probably +/- 0.025g for the typical user). It is critical to control all of the above stated factors.
How important is +/- 0.025g? If your object was 1.000g, this is +/-2.5%. But if you are trying to measure something that is 10mg (0.010g), this is a variation of +/-25%. The smaller the weight, the larger the % variation. I can understand why many reviewers are frustrated at trying to measure something as small as a few milligrams.
Another design flaw with this is the height of the plastic cover. When the 10g weight is placed on the scale standing up, the lid is not able to close. And because, as mentioned above, of the tension in the lid transferring through the hinge and onto the scale itself produces variance in the readings as much as +/- 0.016g, and this can vary by the degree of opening, the only way to get repeatable measurements is to always have the lid closed. This means that the two standard weights can not be standing vertically but must be lay down horizontally, and it can roll side to side until it stabilizes. It also means that the objects you wish to weigh can not exceed roughly 7 mm in height. Any taller and it touches the lid. Larger objects would require the lid to be open to measure, but now we question the accuracy again due to the tension of an opened lid.
It does not appear to be sensitive enough to measure the weight of fingerprints.
Conclusion: This scale is probably best if you wanted to weigh objects near or greater than 1.0 g with an approximate accuracy of +/- 0.025g (+/- 2.5%). The heavier the object, the varience by % is smaller. (e.g. 10g +/- 0.25%). Smaller objects less than 1.0g would result in larger % errors. If you want to measure smaller items and with a greater degree of precision, you'll need to buy laboratory grade scales.
If you control all the stated factors above, and test your own unit for variations, if every factor is controlled, variation in measurement of same object might be limited to +/- 0.002g.
Otherwise, good for general purposes such as measuring the weight of jewelry.
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