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Topic: Quality and Precision of Cheap Analytical Balances  (Read 277 times)

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Offline mdxx95

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Quality and Precision of Cheap Analytical Balances
« on: May 23, 2019, 08:36:43 AM »
Dear Fellow Chemists or Enthusiasts,

Do you think that these analytical Balances are worth it?

https://www.ebay.co.uk/itm/PRECISION-SCALE-200-x-0-001g-LABORATORY-DIGITAL-ANALYTICAL-WEIGHING-BALANCE/283352903826?epid=1955735745&hash=item41f9263092&enc=AQADAAADAFjVrDbVsZ8oH%2F8PNHtt9VX4%2Fw7FZcmMuqsX8uaFEduV%2BF05YrCje7W8ygoxdtzrrYQUZjMNLBtTgUdZT99cTZpgMyEcW3MZxKrd1HhrQlAp3csJ8iqSBpXfOp5L2fhi28c5gSX1iqO0rwaRyvG3IfDj7drZXgyA86TNqoV7jJlLOyNweEecHMZ757t3W0DM5cUR7arp57UyWJUUbH9%2B5X%2BvvJcB6Qw31GADBW34UnhNmj%2Fi3EGh6m8CpFwzgGsYkyGjaXv8ZqdWNDbbjt4H9KENbj723BSsSLYWXGgnNjSB%2BHimRsX1FfolA0QiZt1F8ecFWDnn3ukD58PIFCm2jie15%2FbxtzoWOT4Bq26mimpdDQYVhgdR%2FStrfSWWsMjmrL7i6ttYdppl1qxVrGZTXk4rXqZwesddD4oRCSmBJXCD9FQwL%2B6%2FYum13SSPDJHImrXL8xvtIHO0v7p2sTfzfZBRMG%2FJLgZ%2F%2BhgJakxrovq78VQh8PEFVGHEVqorZM5nbxSPeFYPtOELY9h2dYTDfzXeninIUkkvXRvybfOuizLXVpD2yrHUHhrIyIGvWcU4Ew1UNpAZXQloP5cYlVCaAGXAJsvr0sXTO53FseCe%2Fjcq2%2BdURavMxk8eHfcn0n%2FK8QjqnluwGMUNXTa20DPydcGN3i40OcLoBrlEjHJSSzlLzkmqncGqvAUqt%2FjfV8vyndSD9gjYVTPM0k%2ByWNGlBltIMgzmtYpugLeaJ3lFMj%2B3LxbrCfniXpOxLkp7gSup9JJCK1YcA9r8dS1FzZzuGpxtzJ02cM56EttPXafx22KaqJ2Wo8%2BwHSccBp8z8ip4ql8J8ShMYOsr3wsqJDcXRID%2FyZAofoxrULkwH7kv%2BrC5svjxBgUPBd%2Bh6t5xwb5u%2BDLF7P%2BfzIxAbiucrQgD4aS71M4qnNc5NWYxUF26U1M9Z%2FpgAbKwaoN%2FpBdmqI6AVOBKj7k2%2FZ253inKNGMQd%2FaLb1lCOfe8cBL%2FIlrgkfBef%2FTzhMORa0A4eR35gCepPQ%3D%3D&checksum=28335290382669a358f0b3ac427bb81128dd240eb824


Or are they a waste of money? For example we would like to use it for measuring the hygroscopic water content of coal or other solid fossil fuels.

Sorry for this lousy link


Offline jeffmoonchop

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Re: Quality and Precision of Cheap Analytical Balances
« Reply #1 on: May 23, 2019, 12:30:45 PM »
Its only 3dp, not very accurate for measuring small quantities of water. Depends how accurate you need to be but I'd always be happier with 4dp, ideally 5dp.


Offline pcm81

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Re: Quality and Precision of Cheap Analytical Balances
« Reply #2 on: May 25, 2019, 03:29:37 PM »
I have that exact balance, but i bought mine on Amazon. I verified its accuracy with Mettler Toledo 11123059 CarePac Customized 3rd Weight OIML, Class E2 100 g Weight and it was good. If 1 milligram is good enough resolution for you, then go for it. If you are measuring things that are 5mg in weight, then you need a different scale, b/c 1mg will be a 20% error with such small weights.

What i found is that reading varies slightly depending on there i place the weight. In center of the plate it was spot on, at the edges it was +/- 8mg with 100g weight.

The comment above about 3dp is wrong. With 100g load it is 6dp.It reads up to 200g with 1mg resolution, so something like 127.134.

It works better plugged in than on batteries. With not a brand new battery mine failed to completely load, even though display lit up.
« Last Edit: May 25, 2019, 03:50:51 PM by pcm81 »

Offline jeffmoonchop

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Re: Quality and Precision of Cheap Analytical Balances
« Reply #3 on: May 25, 2019, 11:31:35 PM »
I think you're talking about significant figures, not decimal places like I was.

Offline pcm81

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Re: Quality and Precision of Cheap Analytical Balances
« Reply #4 on: May 26, 2019, 09:59:57 AM »
I think you're talking about significant figures, not decimal places like I was.

Correct. I misspoke. But significant figures is the important part. You can have a very accurate and super expansive scale with 6 significant figures and 0 decimal places measuring in micro grams or a very cheap and not very accurate scale with 3 decimal figures measuring in kilograms. It most certainly is nice to go to 0.1 of milligram, but for a kitchen chemist ease of use is also important; so a scale with 200g range allows one to use glass beaker and get 0.1-100g mass of whatever measured accurately. If you are working in a real lab and need to study samples that are 1 milligram in weight; then definitely this scale is not for you.

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