Professsional, Precision Scales - Page 1
Forum section: electronics / general

author: olsenn
author_rank: Frequent Contributor
timestamp: April 11, 2014, 02:30:00 am
content: I am looking for purchase a laboratory grade scale capable of measuring accurately and precisely to 0.0001g (100ug). I know little about brand differences when it comes to these things; however, it is important that this device be as accurate as it is precise! If I am trying to measure 100ug of a substance and this thing has an accuracy of +- 200ug, then that will not suit me well!Without much research so far, I have come to the attention of the following models:Intell-Lab™ PX-200:http://www.summitmeasurement.net/Best-Selling-Analytical-Balance-p/px-promo.htmTuning Fork Analytical Balance - HT224:http://www.summitmeasurement.net/VIBRA-Tuning-Fork-Analytical-Balance-HT224-p/ht-224.htmCitizen CY-64 Table Top Analytical Balance :http://www.oldwillknottscales.com/citizen-cy64.htmlMaximum weight is largely unimportant to me. As long as it can accept 100 grams, I should be fine. I just need precision and accuracy as well as obviously a robust and reliable device that will last a lifetime! Any opinions on tuning-fork vs conventional weighing mechanisms etc would be appreciated. If the mentioned choices are in your opinion unsuitable, please comment. I want something reliable and functional.

author: ElektroQuark
author_rank: Unknown
timestamp: April 11, 2014, 06:54:33 am
content: METTLER is the name you are looking for.Look at specifications, a 0.0001 resolution scale may not precisely measure 0.0001g.Also, accuracy is function of the total mass of the sustance to weight. Scales have ranges of total-weith/accurary.For precisely measure 0.0001g you will need a 0.00001g capable scale. Prices go up.

author: KJDS
author_rank: Super Contributor
timestamp: April 11, 2014, 07:08:16 am
content: Quote from: EdoNork on April 11, 2014, 06:54:33 amJudging by the listings of used equipment from the big drug manufacturers, the other name they use is Sartorius.

author: ElektroQuark
author_rank: Unknown
timestamp: April 11, 2014, 07:22:53 am
content: Sartorius is a good brand too, but second to METTLER and with not a comparable support. It may be significally cheaper, look at them too, yes.Look at METTLER as an FLUKE equivalent, well, better than FLUKE i would say.Sorry, but they do awesome machines... I'm somewhat biased.

author: nanofrog
author_rank: Super Contributor
timestamp: April 11, 2014, 08:06:44 am
content: Quote from: EdoNork on April 11, 2014, 06:54:33 am+1If you're after the absolute best IME.

author: rdl
author_rank: Super Contributor
timestamp: April 11, 2014, 01:13:03 pm
content: This is correct. You will need a balance that goes to 0.01 mg, good luck. Probably is going to be very expensive. If possible, maybe you could take a larger quantity of your material and cut it (or dilute it) 1 part to 9 parts of something else. Then you could get by with 0.1 mg accuracy.Quote from: EdoNork on April 11, 2014, 06:54:33 am

author: wraper
author_rank: Unknown
timestamp: April 11, 2014, 01:56:09 pm
content: Both Mettler Toledo and Sartorius are very good. New scales of such precision will be very expensive, used also are not cheap. For example Mettler AX205:http://www.ebay.com/sch/i.html?_odkw=AX205&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xmettler+AX205&_nkw=mettler+AX205&_sacat=0One recommendation if you going to buy used. Check if displayed weight do not drift significant amount (more than some last digits) if you place about 50g weight about 2 cm off center. This is common fault. Also used scales might need to internal calibration weights to be cleaned if they were used in dusty environment. That can easily change internal calibration by 100-150 ug on full scale.

author: PedroDaGr8
author_rank: Super Contributor
timestamp: April 11, 2014, 03:54:09 pm
content: As a chemist, balances like this are what a multimeter is to an EE. Both Sartorius and Mettler-Toledo make good balances. That being said, pretty much every lab I have worked in, the larger "general-use" balances are either Sartorius or MT while the low mass balance are pretty much always MT. I don't know WHY this is but I've yet to use a Sartorius mg balance. In general, I'd say MT supplies about 80% of the balances in chemistry labs.Honestly, the Mettler Toledo AX205 is one of my favorite balances ever.. It has good stability, even on benches with a bit of vibration, completely touchless operation, the display rotates out of the way for easy cleanup, etc. My favorite feature is something at first I felt was a bit gimmicky; it has two proximity sensors which you can map to various functions. I have one sensor mapped to open the motoriozed side doors and the other mapped to tare. This is important when you are measuring toxic materials (such as Cadmium precursors). I no longer have to clean the external surfaces of the scale after I measure CdO. I just come up to the scale, wave my hand over the right one, the doors open. Place my empty weigh container on the pan, wave my hand over the left one, it tares. I am now ready to measure.

author: wraper
author_rank: Unknown
timestamp: April 11, 2014, 04:24:04 pm
content: BTW, need to notice. You can't just put such precision balances on the table. Any vibration will interfere with the measurements. Where I work, we use about 50kg heavy granite plate on the separate stand directly on the floor. Also air movement and temperature is important, therefore no conditioners working nearby while measuring.

author: quarks
author_rank: Frequent Contributor
timestamp: April 11, 2014, 04:27:27 pm
content: besides the already mentioned brands, KERN maybe another choicehttp://www.kern-sohn.com/cgi-bin/cosmoshop/lshop.cgi?action=shopstart&wkid=13972336043206&ls=en&nochache=1397233604-3206

author: Dr. Frank
author_rank: Super Contributor
timestamp: April 11, 2014, 09:44:56 pm
content: Sartorius and Mettler Toledo are the ultimate choices for professional high grade scales.I also recommend KERN for budget solution. They also manufacture professional grade products, and their analysis scales would fit the requirements.Compared to the two other companies, repeatability and stability are worse, although.Frank

author: SeanB
author_rank: Super Contributor
timestamp: April 12, 2014, 04:31:42 am
content: Location is important, as mentioned above you need a separate enclosed area for the balance, and each should be on it's own high mass pedestal isolated from building vibration ( It will detect people walking on the floor next to it) along with a set of certified precision masspieces to do check calibrations. I had mine done last year, and due to a mis communication they did all the masspieces, so I now know that the 5mg small aluminium flakes in the box are 5mg within 2ug. All I needed and use are the10-50g brass blocks, as I only measure down to 10mg commonly.If I need more than 10mg accuracy I pull out the old Ohaus strained wire massmeter, turn it on and leave it for about 4 hours to stabilise, which then gives 1mg accuracy.As well with the accuracy you are wanting please note that at this level you get a mass reading from the IR radiation you emit so you want to make all measurements with the massmeter door closed, as placing your hand near the open door will show a few hundred microgram increase just from your hand emitting IR radiation. Same with room lighting, this is the one application where you want a good diffused light source well away from the unit, and no direct sunlight into the room.

author: PedroDaGr8
author_rank: Super Contributor
timestamp: April 13, 2014, 01:41:10 am
content: Quote from: SeanB on April 12, 2014, 04:31:42 amAre you sure on this? We were always taught it was thermal convection currents from our skin that caused the fluctuating mass issues. I have never had an issue ever with a mG balance and light. I would think light influence would be way lower than tens of uG.

author: nowlan
author_rank: Frequent Contributor
timestamp: April 13, 2014, 01:47:56 am
content: Do these scales really warrant hundreds of dollars?Is there some nist certification required or something?Just wondering compared to my 10-20$ kitchen ones.

author: PedroDaGr8
author_rank: Super Contributor
timestamp: April 13, 2014, 02:30:06 am
content: Quote from: nowlan on April 13, 2014, 01:47:56 amThey aren't even in the same class. Comparing a kitchen scale to a laboratory mass balance is like comparing a harbor freight multimeter to a 7.5 digit lab meter. Much like multimeters laboratory balances have high precision, extremely high degrees of linearity, day to day reproducibility and more digits.

author: peter.mitchell
author_rank: Super Contributor
timestamp: April 13, 2014, 02:57:32 am
content: I don't know why people say these are expensive, I mean, how much did you expect them to cost?

author: SeanB
author_rank: Super Contributor
timestamp: April 13, 2014, 08:20:50 am
content: Just for comparasion call any mass metrology lab and ask them for the price of calibration. 0.1% is cheap ( 1000PPM), 100PPM is about 10 times more and going to 10PPM involves them bringing out the reference working standard they have, and coming out to you to do the cal in your particular location. That will be a set of masses that have a mass known down to the microgram level for a 1kg masspiece. My ones are only 100PPM verified, and as I actually use them and handle the smaller ones with gloves they might stay at that level for years. The bigger 20kg ones will lose material from wear of handling, and this shows as a circa 300mg loss between calibration cycles on them. My ones get used during the external cal cycle as they are more accurate than the ones that have been sitting in a box in the back of the truck that the metrologist uses, as his most common work is shop massmeters that are only 0.1% and they are still good enough for that even with paint flakes missing.