American Weigh GeminiPRO GPR-20 Digital Milligram Scale 20g x 0.001G
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- Weighs up to 20 grams in 0.001 gram increments
- Comes with protective case, tweezers, (2) 10g weights and 2 weighing trays
- The flip-down shield protects the delicate weighing surface
- Powered by 4 AAA batteries (included)
- Backed by a powerful 10 year warranty
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The all new GeminiPRO milligram scale offers a 1 milligram readability with a 20g capacity. The removable weighing platforms make removing samples easy. Great for weighing precious gems and other valuables. All scales backed by our 10 year warranty.
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Relative to the Gemini 20, the build quality is much higher, and the attention to detail is much finer. The scale body, the cover, even the mating of the battery door to the unit just scream of "somebody actually thought about this". My Gemini 20, while reasonably accurate, always sort of half-felt like it could just randomly disintegrate if you picked it up too fast. There's also a very nicely placed mating set of concentric rings between the load cell and the weighing dishes, making it impossible for the dish to slip and contact the scale body. No dime mod needed here!
The accessories it comes with all seem higher-quality too. A very nice vinyl zipcase with foam padded cutouts for the scale and a set of tweezers on one side, and two mesh pockets for the two weighing dishes. This trend does not continue with the included calibration weights though. Both the Gemini 20 and the Pro (once calibrated with a bit better set of OIML M1s) were reading them both as around 10mg underweight. Granted, that won't make a huge difference over the total range of the range of the scale, but it's definitely an issue.
The scale is definitely accurate to +- 3mg or better as claimed in the manual, but like the Gemini 20 it has problems registering very light things. It's just completely off under 10mg, with accuracy increasing up from 10mg to roughly the 25mg mark. Excellent technique and checking with calibration weights is definitely a must when weighing between 10-25mg on this scale.
All in all I'm quite impressed with this scale. The design and construction are well thought out, and it's probably the most accurate scale in it's price range. Recommended.
So, if that is what you're looking for, and if the maximum capacity is all right with you, then read on. Otherwise, you probably need something much more expensive than this.
It's a very nicely made device. Its dimensions:
• Length: just under 6 inches (150 mm)
• Width: 2 and ⅞ inches (72 mm)
• Height: 1 9/16 inches (40 mm) tall.
It is constructed of hard black plastic, with a clear plastic cover on a hinge. (more about that cover later) It comes in a nice, sturdy case with heavy memory foam around the device, and fishnet pockets that hold two trays when not in use. The trays are round, concave, and very lightweight, less than a penny in weight. One tray is deeper than the other and has a tiny lipped pour spout, with a tiny handle at 90 degrees from the spout. It takes tweezers to use these, and indeed tweezers come with it, in their own slot in the case. Also included are two calibration weights of 10 grams apiece. A label on the lid of the scale recommends calibration before each use.
The scale is very sensitive. At 1 thousandth of a gram accuracy, even a breath could change the measurement, thus the hinged plastic cover that completely encloses the scale's surface and trays, along with most of the kinds of things I can imagine that would fit within its max capacity. The top closes and opens with one-handed ease, yet seals firmly. No problem there.
In addition to grams, it also measures in dwt (pennyweight), grains, and carats, making it useful in a variety of applications. The Mode button quickly switches units.
The "Tare" button zeroes it for starting with a tray or whatever else may be on the scale (the capsule of a pill, for instance) that you don't want to include in the measurement.
A fourth button is labeled "Ucal," and is nothing more or less than a calibration button. The instructions come with the device, and they utilize both weights to calibrate it. There's nothing tricky about it. Just start, push the Ucal button, and do two measurements on cue. It tells you when it's done.
I bought it for its accuracy, but I rarely use it, because I don't work with those kinds of things very often. On the few occasions that I've really needed to use it, it more than paid for itself. The price is right for a device this sturdy and sensitive. I think you should know if its capacity suits you. If so, I cannot think of any reason why this scale would not serve your purposes, short of working on the atomic level. If that's your need, you aren't reading this review; you would be in a pro lab instrument company looking at devices that cost tens of thousands of dollars. For what this is, it's an excellent scale for household medicine, small labs or jewelry makers.
Note: you do need to caliberate it before using, and I recommend that you re-caliberate it every so often to keep it in good working condition.
Important note: this scales is extremely sensitive to any draft - even the slight draft from the vent of the room's air-conditioner is enough to cause fluctuations of a few milligrams. In fact, even the slight disturbance in air currents from a fan a little distance away, that is blowing AWAY from the scales, creates all sorts of inaccuracies. Therefore, ensure that windows, doors, fans, and airconditioners, are all SHUT/POWERED-OFF during the use of this weighing scales.
I had one of these before, and it lasted three years of DAILY use (multiple times each day, measuring out dosages of medicines and supplements for our many many kitties) before becoming wonky - so I expect this should last that long too - which is pretty decent considering the price.