Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
Author: Subject: High precision analytical balance/scale 120g at .001g & 6kg at .01g resolution
RogueRose
International Hazard
*****




Posts: 1513
Registered: 16-6-2014
Member Is Offline


[*] posted on 4-5-2017 at 21:02
High precision analytical balance/scale 120g at .001g & 6kg at .01g resolution


This is US based but would ship internationally if needed.

I'm wondering if many/any of you have interest in analytical balances ("scales in common terms) that are very accurate and can display in 5-10 different weights like grams, grains, carats, etc. These are ones that are used in labs and industry.

I've been getting some from a few auction houses and have had complete success with all the ones I've ordered and they have been MUCH more accurate than the digital scales found on Amazon and other online stores for $10-50. I've seen some of these balances close at auction for $20 once in a while, but most are a little more than that with $30-45 on average (with whatever auction fee and "hammer fee".... usually about 25%) These models sell for $150-250 on ebay and are $250-700 new.

Many of these are sensitive enough that a protective chamber may be needed for very accurate use, but I haven't found a need for that for my purposes. The readout may vary by +/- .003 without the enclosure but that is still close enough for most purposes. I haven't seen many of the balances with the enclosure included except for the really expensive models that are $1000+

There are also balances that are good for 4-6kg (some up to 12-15 even) with resolution of .01g at that weight. These are prices about the same and I've never seen enclosures for these. The pricing is about the same both at auction cost and retail, so there are some good deals that I have seen.

I have seen some inexpensive scales on ebay and amazon that state they do .001g or at least .01 and they use a mechanical stress sensor which are notorious for loosing accuracy ofter some use or even from the manufacturer. These scales often sell for $15-40, new, on those big sites, but I've found some MAJOR discrepancies in weight of 20-50% from what they were supposed to be. After going through 3 scales and messing up a lot of experiments, I decided to find a lab quality scale which is why I found those mentioned above. Unless you have other scales to check against these cheap ones, you may never know why your experiments aren't working correctly and it is SUPER frustrating!

I'd have to say a good balance is one of the best investments you can make if you are working in this hobby.

If you have interest in these, let me know and I can keep an eye out for them in the auctions I'm bidding in. I could have them shipped directly to the customer via UPS as they pick up my items from the auction house - and it would save on paying 2 shipping charges.

I also find really good deals on all kinds of hot plates from small ones of 30w up to 1320w units - many have stirring built in. $20-45 usually Most units are Chemglass or VWR.

Also there are vortex shakers (or vibrators..??) that either stir test tubes/vials/bottles or something but there are a lot of these in good shape for $20-45 usually

Professional PH highly accurate testers (retail $400-1000) going for $30-50 - sometimes the testing probes need replaced. These are so much better than the $20-50 units on amazon that I've used in speed, ease of use and accuracy.

There's a lot of other equipment - just about anything found in a lab you can imagine. I just missed a fully functional rotovap the other day that went for $100 so I'm kicking myself for that one. That's not normal, many sell for $300-700 depending on model.

Any questions feel free to ask.
View user's profile View All Posts By User
JJay
International Hazard
*****




Posts: 3411
Registered: 15-10-2015
Member Is Offline


[*] posted on 4-5-2017 at 21:26


If I had seen this a few weeks ago, I probably would have bought a scale. I ended up getting one of those el cheapo ones off Amazon. Prior to calibration, it was off by six milligrams weighing a 10 gram lab standard.



View user's profile View All Posts By User
RogueRose
International Hazard
*****




Posts: 1513
Registered: 16-6-2014
Member Is Offline


[*] posted on 4-5-2017 at 23:18


Quote: Originally posted by JJay  
If I had seen this a few weeks ago, I probably would have bought a scale. I ended up getting one of those el cheapo ones off Amazon. Prior to calibration, it was off by six milligrams weighing a 10 gram lab standard.


If it is one of those rectangle (black) scales with a stainless platform maybe a little larger than a business card, with 3 buttons, I've gone through 5-6 of these over the years and they have sensor creep, which is caused by low quality metal that is used for the stress sensor. With use, they will get less and less accurate the higher the weight being weighed. It maybe accurate with a 5g mass (nickle) but if it goes to 200g, 500g, or 1kg, it maybe off 2-3% and you'd never know it unless you have a standard of higher mass like 500g or so.

Using a low mass standard is a recipe for disaster for these scales b/c the stress is so low on the measuring arm that the small % it is off can't be seen.


I found out the hard way when measuring lye for soap and it was off by almost 40%! and made some very harsh/caustic soap.....
View user's profile View All Posts By User
JJay
International Hazard
*****




Posts: 3411
Registered: 15-10-2015
Member Is Offline


[*] posted on 5-5-2017 at 00:20


The particular scale I'm talking about has a max weight of 20 grams and calibrates with 10 gram and 20 gram weights. I assume it does parabolic interpolation.

I don't mean to suggest that I don't believe that a lab scale is superior in every way, but for a scale to be off by 20% means that something is really wrong. How much is it for a lab scale with an enclosure that weighs to 0.0001 grams?




View user's profile View All Posts By User
RogueRose
International Hazard
*****




Posts: 1513
Registered: 16-6-2014
Member Is Offline


[*] posted on 5-5-2017 at 11:09


Quote: Originally posted by JJay  
The particular scale I'm talking about has a max weight of 20 grams and calibrates with 10 gram and 20 gram weights. I assume it does parabolic interpolation.

I don't mean to suggest that I don't believe that a lab scale is superior in every way, but for a scale to be off by 20% means that something is really wrong. How much is it for a lab scale with an enclosure that weighs to 0.0001 grams?


Yeah and it was my newest scale so I trusted it. I also changed batteries many times thinking it could be something with low voltage giving a bad reading.

After the one batch I made that acted strange, I measured out ingredients in 6 bowls and things looked off, just by my eye, so I weighed again and they were right (according to the scale). So I got an older scale out that had bad buttons but was still accurate and checked and it was 17-23% depending upon the mass - the higher the mass the more it was off. I guess that makes sense if calibration takes place at a low weight like 1-5 grams. The scale did go through those 3v button batteries like crazy, using about 2 every other week but they were cheap chinese batteries so IDK if it was the scale or batteries.

AS far as one that weighs in micrograms? I really don't know as I would guess they may be different than the mechanical stress scales but can't say I know how it is done for that.

Does yours do micrograms?

I've always wondered how much difference it makes if the scale isn't 100% level or if something like a rubber foot/bumper is missing. That's one thing I really liked about the scale I just got, it has adjustable feet (screw in and out to level) and a built in bubble leveler that centers in a dome when it is perfect in all 4 directions.


[Edited on 5-5-2017 by RogueRose]
View user's profile View All Posts By User
yobbo II
National Hazard
****




Posts: 377
Registered: 28-3-2016
Member Is Offline

Mood: No Mood

[*] posted on 6-11-2017 at 14:27


Would like to own this baby. I have a fetish for ferociously complicated contraptions. Is it sensible to purchase

https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p238...

[Edited on 6-11-2017 by yobbo II]
View user's profile View All Posts By User
PiledhigherandDeeper
Harmless
*




Posts: 17
Registered: 17-3-2013
Location: USA
Member Is Offline

Mood: No Mood

[*] posted on 6-11-2017 at 15:06


Quote: Originally posted by yobbo II  
Would like to own this baby. I have a fetish for ferociously complicated contraptions. Is it sensible to purchase

https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p238...

[Edited on 6-11-2017 by yobbo II]


As a mechanical conversation piece? Definitely.

For pretending that you have an accurate mass down to the microgram while using it in your kitchen? Whatever floats your boat.

For being able to measure down to the microgram (accurately) without having it validated by a professional / having a specialized weighing area setup / having a way of handling items down to the microgram level, let alone a need? No.

Higher precision and accuracy --> more upkeep / preventative maintenance, more careful technique, specialized setups (automatic doors, draft prevention, static dissipation, stable bases perhaps down to building structure), time on task, know how, and most all a practical need.

This kind of reminds me of the line from Tommy Boy:

"Because they know all they sold ya was a guaranteed piece of shit. That's all it is, isn't it? Hey, if you want me to take a dump in a box and mark it guaranteed, I will. I got spare time."

Thats not to say a professional balance CAN'T mass to an recockulous number of significant digits, but that the average Joe would really never know. Heck, I work with professional Joe's who just received 2 $10K balances, because it's really at the limit of what they can do with them (they weigh and package compounds on request)... they could have gotten much more expensive ones, it just wasn't practical for any parties involved.

A more cynical chemist colleague of mine had a good laugh at the prospect of 0.000001 accuracy... "Like we'd know any better; we sure can't weigh at that level!"

[Edited on 6-11-2017 by PiledhigherandDeeper]
View user's profile View All Posts By User
yobbo II
National Hazard
****




Posts: 377
Registered: 28-3-2016
Member Is Offline

Mood: No Mood

[*] posted on 7-11-2017 at 18:11


That settles it once and for all. I'm buying it!:D
View user's profile View All Posts By User
NEMO-Chemistry
International Hazard
*****




Posts: 1560
Registered: 29-5-2016
Location: UK
Member Is Offline

Mood: No Mood

[*] posted on 7-11-2017 at 19:07


funny how some the fundamentals of chemistry where weighed using a razor blade and fulcrum.
I would love a balance down to 1mg, or a very old wooden case one. realty is though does it help to weigh to 1mg?After all most use chemicals with a purity less than 99%.

Or take say copper sulphate, lets assume you need 21.232g of it. Even if your balance says 21.232g, by the time you weighed it etc how much of that is copper sulphate and how much of it is water?
isnt 2 decimal places more than enough for most things?
View user's profile View All Posts By User
Eddie Current
Hazard to Self
**




Posts: 78
Registered: 25-7-2018
Member Is Offline


[*] posted on 10-6-2020 at 21:23


Greeting SM folks, I am wondering if I can get any feedback from you good folks regarding the cheaper lab scales found on Ebay. I am in Australia and we are not spoiled for competitive pricing here with nice precision equipment, and these advertised scales are around $1,000 cheaper than those that are typically purchased at the local laboratory equipment suppliers.

Cheers, Eddie.



https://www.ebay.com.au/itm/200-0-0001g-0-1mg-Digital-Precis...
View user's profile View All Posts By User
Sulaiman
International Hazard
*****




Posts: 2935
Registered: 8-2-2015
Location: UK ... on extended Holiday in Malaysia
Member Is Offline


[*] posted on 10-6-2020 at 22:02


I have had a made-in-China FA2204G analytical balance for about 9 months,
things to consider;

specified repeatability
specified linearity
maximum weighing capacity

e.g. my balance is 220g max, my 100ml +/-0.08ml volumeric flask weighs 68.8072(5)g.
so the maximum density that I can measure is 1.51
so for higher densities I would need a 50ml volumetric flask - which will be a little less accurate

To repeatably measure to this precision and accuracy my balance needs to be 'warmed up' for at least a day in a continuously air conditioned room,
then re-calibrated.

Accuracy is determined by your calibration weights - I use E2 class (+/-1.6 ppm) which are not cheap.
E1 class are more expensive than the balance and unnecessary in my case as I don't trust the balance to better than 0.5mg.

Also, your flask and liquid need to be at a stable, accurately measured temperature then compensations need to be calculated.

And an air-dried flask is not really dry !

My balance can do single point callibration or a six-point linearisation calibrations
- which needs four accurate weights, 0, 50, 100, (100+50), 200, (200+20)

The print functions are useful - I needed to buy a USB-to-RS232 converter to use it with my laptop.

So, buying an analytical ballance is not cheap,
maintaining its calibration costs more !

You need to ask yourself if you really need an analytical balance,
the answer is no, not for typical hobby chemistry.
But it is nice to have one :)




CAUTION : Hobby Chemist, not Professional or even Amateur
View user's profile View All Posts By User
Ubya
International Hazard
*****




Posts: 1124
Registered: 23-11-2017
Location: Rome-Italy
Member Is Offline

Mood: I'm a maddo scientisto!!!

[*] posted on 11-6-2020 at 01:47


exactly what sulaiman said, plus another thing, you could have a balance that measures 0.01mg, and pay a lot for it, but you can't use it on a table, even the most stable surface is not stable enough. At university I had to use one in the quantitative analytical lab, the "benches" for the balances were solid concrete structures bonded to the floor, and if someone walked behind you while taking a measurement you could see the numbers floating on the display.

so you could buy a 1000$ balance, a 1000$ calibration weight, and then benefit nothing from it because your house is shakey.





---------------------------------------------------------------------
feel free to correct my grammar, or any mistakes i make
---------------------------------------------------------------------
View user's profile View All Posts By User
Sulaiman
International Hazard
*****




Posts: 2935
Registered: 8-2-2015
Location: UK ... on extended Holiday in Malaysia
Member Is Offline


[*] posted on 11-6-2020 at 05:35


One mildly interesting thing,
my balance came with a single calibration weight, 200g class F1.
Comparing this F1 weight with my E2 200g weight over many weighings,
the difference is only 0.13mg.

One minor observation, the zero on my balance drifts quite a lot, I have to use the zero-tracking option
or manually zero the reading quite frequently.
Although the zero drifts, the difference between no weight and 200g drifts very little.

Your desire for precision and accuracy should take into account the purity of whatever it is that you weigh,
e. g. 1mg in 100g is equivalent to 99.999% purity,
not many chemicals are available with such purity.

For practical purposes,
I am very pleased with myself if I can achieve titrations repeatable to 0.1% and accurate to 0.2%.

One more...
I chose an analytical balance that has an optional hook below the pan to allow for density measurements,
not used yet as a firm elevated base with a hole in it is required.




CAUTION : Hobby Chemist, not Professional or even Amateur
View user's profile View All Posts By User
Eddie Current
Hazard to Self
**




Posts: 78
Registered: 25-7-2018
Member Is Offline


[*] posted on 11-6-2020 at 15:28


Great feedback, thanks.

I think when all is considered, the $700 could be spent better elsewhere.
View user's profile View All Posts By User
Refinery
National Hazard
****




Posts: 370
Registered: 17-2-2014
Member Is Offline

Mood: Still

[*] posted on 12-6-2020 at 08:23


I suppose you could calibrate the scale with weighting a known item, like coin (or a bulk of them) and if the scale corrects, you could make a precision weight yourself from anything that is stable, like piece of metal.

Unless calibration weights are cheaply available, of course. Haven't checked.

But this way one can check that the scale is working right before measuring reagents.

The scales I've bought from a supermarket are surprisingly sturdy and accurate. I've got a total of four of them, one which is 0.01g, and they all have hold their calibration within few grams, and the precision one consistently reports same weights with coins.

For amateur use, I would rather spend that extra few bucks for hitting a junkyard and getting a solid block of steel or couple for calibration than buying a 1k$ lab scale, unless precision is really required. Measuring dissolved gases, volume-weights etc could be easier with high grade scales.
View user's profile View All Posts By User
Ubya
International Hazard
*****




Posts: 1124
Registered: 23-11-2017
Location: Rome-Italy
Member Is Offline

Mood: I'm a maddo scientisto!!!

[*] posted on 12-6-2020 at 09:12


Quote: Originally posted by Refinery  
I suppose you could calibrate the scale with weighting a known item, like coin (or a bulk of them) and if the scale corrects, you could make a precision weight yourself from anything that is stable, like piece of metal.

Unless calibration weights are cheaply available, of course. Haven't checked.

But this way one can check that the scale is working right before measuring reagents.

The scales I've bought from a supermarket are surprisingly sturdy and accurate. I've got a total of four of them, one which is 0.01g, and they all have hold their calibration within few grams, and the precision one consistently reports same weights with coins.

For amateur use, I would rather spend that extra few bucks for hitting a junkyard and getting a solid block of steel or couple for calibration than buying a 1k$ lab scale, unless precision is really required. Measuring dissolved gases, volume-weights etc could be easier with high grade scales.


oh boi, you are comparing a kitchen balance to an analytical balance.

a random piece of metal is not accurate at all, it could rust, adding weight, and by cleaning it you remove material.

coins are accurate to maybe to the centigram, not to the milligram.

you said you can make your own calibration weights, yeah, only if you have a balance more accurate than the one you want to calibrate, you can't use the same balance to calibrate itself.

the idea of using random pieces of a known weight to check a balance is ok for lower end balances, if you spend $1k+ for a precision balance, and then expect to calibrate it with a coin or a random piece of metal, you kinda wasted your money

[Edited on 12-6-2020 by Ubya]





---------------------------------------------------------------------
feel free to correct my grammar, or any mistakes i make
---------------------------------------------------------------------
View user's profile View All Posts By User
Mateo_swe
Hazard to Others
***




Posts: 149
Registered: 24-8-2019
Location: Within EU
Member Is Offline


[*] posted on 12-6-2020 at 09:21


I have been wanting one of these Ohaus tripple beam scales for a while.
I actually ordered one of the older ones with a dial from US, but sadly it arrived in pieces from rough shipping and not good packing in the box.
The reason i want one of these are that they are very good scales and if cared for they can last forever.
No electronics that can fail or batterys that are bad when you need to use it.
They dont have any mg precision, maybe 0.1g something but they can weigh up to 2.6 kilos.
These are very nice in a hobby lab and will last forever if you take good care of it.
I have heard so many recommend these scales.
I will buy one some day and im really looking forward to that moment.


Tripple beam scale 2.jpg - 44kB ohaus scale.jpg - 94kB
View user's profile View All Posts By User
Refinery
National Hazard
****




Posts: 370
Registered: 17-2-2014
Member Is Offline

Mood: Still

[*] posted on 12-6-2020 at 09:37


Quote: Originally posted by Ubya  
oh boi, you are comparing a kitchen balance to an analytical balance.


That's my whole point. A $5.99 balance vs $1k balance. It can easily get 99.9% accuracy of the latter. Where the last thous matter, you need to up your stuff. The el cheapos have served me surprisingly well.

About coins, they are the most readily available items of specified weight. They do have deviations, but using a stack will bring the median to a close. Should be well enough to calibrate 0.Xg scales.

http://yehar.com/blog/?p=1193

http://jse.amstat.org/v14n2/datasets.aerts.html

[Edited on 12-6-2020 by Refinery]
View user's profile View All Posts By User
Ubya
International Hazard
*****




Posts: 1124
Registered: 23-11-2017
Location: Rome-Italy
Member Is Offline

Mood: I'm a maddo scientisto!!!

[*] posted on 12-6-2020 at 10:36


Quote: Originally posted by Refinery  


That's my whole point. A $5.99 balance vs $1k balance. It can easily get 99.9% accuracy of the latter. Where the last thous matter, you need to up your stuff. The el cheapos have served me surprisingly well.


you can't compare them as they are used for different things, if you need to weight a compound for a synthesis 99.9% of the time 0.01g accuracy is way more than enough, but for analytical chemistry, that's garbage.






---------------------------------------------------------------------
feel free to correct my grammar, or any mistakes i make
---------------------------------------------------------------------
View user's profile View All Posts By User
Sulaiman
International Hazard
*****




Posts: 2935
Registered: 8-2-2015
Location: UK ... on extended Holiday in Malaysia
Member Is Offline


[*] posted on 12-6-2020 at 14:32


Coins are a poor choice for calibrating scales accurately, maybe 1% accuracy.
I have uncirculated silver silver coins that have a surprising variation in weight,
I even have a gold maple coin and that weighs more than its nominal weight.

Cheap Chinese calibration weights can be within nominal specifications,
but dont rely on it - some quick videos that I made;
https://www.youtube.com/watch?v=1SrUu2ai3P0
https://www.youtube.com/watch?v=kms21glg83M&t=8s
https://www.youtube.com/watch?v=lctwj58ZfMs

I bought a triple beam balance just before I left UK and I have not tested the calibration yet,
but the knife edge bearings seemed to be in good condition.
I will make a video of calibration when able.

I have been using cheap Chinese 300g x 0,01 g scales for a couple of years,
seems accurate to about +/- 0.03g wich is more than adequate for almost all hobby chemistry.

If your scales have acceptable linearity errors then;

. you can make your own test weight
(to check that you get a similar reading each time you use the scales)
but it would be better to buy a cheap calibration weight.

. you can check calibration to a fraction of one percent by determining the density of water - if you have a volumetruc flask.

. if you weigh all chemicals used in an experiment then even if the absolute weights are inaccurate,
the relative weights will be correct,
so calculations for stoichiometry and yields will be correct.

Kitchen scales or low precision scales can be factory calibrated,
but precision scales can only be calibrated in their place of use,
gravity varies with lattitude and altitude.
(and to some extent, geology)




CAUTION : Hobby Chemist, not Professional or even Amateur
View user's profile View All Posts By User
Dr.Bob
International Hazard
*****




Posts: 2170
Registered: 26-1-2011
Location: USA - NC
Member Is Offline

Mood: No Mood

[*] posted on 12-6-2020 at 16:21


I have a few odd lab balances ranging from simple beam to pan balance to a fully enclosed analytical one that cost $1000+. Biggest challenge is making sure that they still work and then shipping them and having them still work. I am always hesitant to sell on Ebay, as shipping is tough and the buyer may say that it does not work, ship it back and with two shipments, probably won't ever work again. So I would love to hear what people think about testing, selling, shipping, and verifying labv balances.
View user's profile View All Posts By User
AvBaeyer
International Hazard
*****




Posts: 533
Registered: 25-2-2014
Location: CA
Member Is Offline

Mood: No Mood

[*] posted on 12-6-2020 at 17:59


I bought an analytical balance on eBay once which was guaranteed to be in working condition. It was shipped FedEx and was delivered to my driveway with the "this side up" arrow pointing to the ground. Upon opening, parts were everywhere. I managed to get everything back to where I thought it all belonged but the balance never worked again. I gave it away. The seller refunded the balance cost but not the shipping which was significant. Lesson: If you are thinking of investing in a real analytical balance, buy local.

I invested in a high quality laboratory scale (ca $250, American made) from a real balance dealer. It came properly packaged and works wonderfully for anything I need.

AvB
View user's profile View All Posts By User
Mateo_swe
Hazard to Others
***




Posts: 149
Registered: 24-8-2019
Location: Within EU
Member Is Offline


[*] posted on 13-6-2020 at 13:45


How strange you didnt get the shipping fee back.
I also bought a scale from US that arrived in many pieces.
EBAY said i get everything back including all shipping, everything, and i did get it all back.
First the seller wanted me to ship back the scale but as he had to pay the return shipping he then said to just send the weights.
Next day i got a message to throw everything away because the return shipping was high even just for the weights.
So i got back what i payed for the scale, plus all shipping fees and i still have the broken scale with weights somewhere in a box.
I know some sellers write on their item pages that they dont pay return shipping, but it seems they must do that anyway.
Maybe its new ebay rules.
View user's profile View All Posts By User

  Go To Top