Scale for specific gravity test?

Coinosaurus

Can anyone recommend a good scale (reasonably accurate, not too expensive) for specific gravity testing?

BruceS

http://m.ebay.com/itm/3000g-x-0-1g-Digital-Scale-Jewelry-Gold-Silver-Coin-Grain-Gram-Weight-Pocket-/281731124561?epid=1849323613&hash=item41987bcd51:g:tFcAAOSwHnFVil1U&_trkparms=pageci%3A093aa7de-8492-11e7-a3f4-74dbd18049d3%7Cparentrq%3Af8a04cab15d0a9e46da2119efffd0c41%7Ciid%3A8

Cheap but effective.

Cameonut

In my mind, it is hard to recommend a scale without knowing more about what you are testing and the weight of the samples. I've bought several small and inexpensive scales and all have worked great. I'll assume you are measuring solids and not liquids or gases.

For example, the scale that BruceS suggested has a resolution of 0.1 grams and a capacity of 3000 grams. This is great for most uses but if the sample you are working with is only a gram or two, this scale won't give you accurate results. But if your sample is 100 grams, this scale would work fine. If you want accuracy of 1% then this scale would do the job for samples weighing 0.1 x 100 = 10 grams or more.

There are a number of similarly priced scales on Ebay that have a resolution of 0.01 grams but the capacity is lowered to about 200 grams. This would give you accurate results if your sample is 1 gram or more. If you need even better resolution of 0.001 grams, they are also available, but significantly more expensive. Also, at extreme resolution, you have to watch for the impact of wind drafts and even drafts from the cooling of hot samples.

Depending on how precise you want to be, it might also be useful to buy a calibration weight that is similar in weight to the samples that you are working with. This way you know the scale is working and measuring properly. I have a 10 gram weight that I use to check my scales. These can be found on ebay for a little more than $5.

Hope this is helpful.

ricko

Great advice by Cameonut....I have two scales...one for lighter samples and one for heavier weights as he described. I also recommend the calibration weights. There are good scales that also allow for different scales... i.e. grams, oz. etc.....Cheers, RickO

MrHalfDime

You cannot use a platform scale, such as those recommended by others here, to perform specific gravity tests. You need a balance beam scale in order to make the required mass measurements of the specimen, first suspended in water, and then a dry measurement. There is no practical way to measure the mass of the specimen suspended in water using a digital platform scale. I have found the Ohaus Cent-O-Gram 311 to be ideal for this purpose. testequipmentdepot.com/ohaus/scales/mechanical-scales-balances/300-series/dial-o-gram-and-cent-o-gram-mechanical-balance-311g-311-00.htm?ref=gbase&gclid=EAIaIQobChMIk8Ky663j1QIVGZ7ACh1RxQGpEAYYASABEgK5CfD_BwE

I use a piece of thin thread, formed in a sliding loop, to suspend the specimen in a beaker of distilled water for the 'wet' measurement, and then use the platform in the normal manner for the 'dry' measurement. The 'accuracy' (more properly, resolution) is 0.01g, more than enough for most coins. I have used my Ohaus 311g for many years now to identify off-metal, counterfeit coins, and have been very pleased.

Disclaimer: I simply Googled the Ohaus Cent-O-Gram 311 g, and copied one of the first spec sheets I found. I have no experience with this specific seller, and do not necessarily endorse them. They are shown merely for an example. With a little shopping, you should be able to find competitive quotes.

1630Boston

Some platform scales are also 'weigh below' scales and would work for specific gravity testing.

MrHalfDime

"Some platform scales are also 'weigh below' scales and would work for specific gravity testing."

Good information. Thank you for sharing that. Yes, when equipped with such a 'weigh below' hook attachment as you describe, a platform scale could be used for the specific gravity 'wet' measurements. However, one would need to fabricate some sort of platform or table with a hole through it to support the scale above, and suspend the specimen below. This would not be necessary when using a balance beam scale, as everything required is included within the scale itself. I guess it would depend upon how many specific gravity tests you are seeking to perform, over how long a period of time.

1630Boston

I actually over see the performance of hundreds of tests per year in my lab, for work.

Insider2

While @1630Boston is surely an expert and eclipses my limited knowledge on the subject, he said: "Some platform scales are also 'weigh below' scales and would work for specific gravity testing."

While true, THIS: Ohaus Cent-O-Gram 311 g

According to the classes I've attended and personal use for decades, THE ONLY and least expensive/easiest to use balance needed for home and coin shop sp. gr. determinations. PERIOD

PS You can even do much larger medals that do not fit in the beaker of warer small enough to fit on the pan. I keep mine ready to go around the clock taking aprox. 20 or so measurements a week!

RogerB

[If you get the Deluxe Super Size model you can also do body fat index measurements. But leave the rubber ducky on dry land.]