Weight - Stimulants' guide for mg level weighing equipment & methods

[Stimulants]

This guide will discuss the equipment and methods for weighing samples in the mg level.

The basic:
Accuracy - how close it is to actual weight.
Precision - how consistently it reads the result for the same weight.
Display resolution - the smallest change that can be seen on the screen.

Ideally, measurements should be accurate & precise as possible.

Equipment:
Specs are usually given like this:
210g x 0.0001g. This means that the instrument can handle up to 210g and read out to 0.1mg.

Testing methods: if any of these fails badly, the scale just sucks or it is damaged. Please read this part thoroughly. This comes ahead of "selection", because it explains the basics needed for proper selection.

Linearity:
+/- 0.4mg. This means how consistent the instrument holds the sensitivity across the entire range. For example, let's say the instrument reads a nickel at 4.9844g with nothing on it. A perfectly "linear" instrument will read 4.9844g when it is loaded with 50% the rated weight, then zero'd (tare) and a nickel placed on top of it. Although it is not very useful, it is a good test to perform on a used scale.

Repeatability/precision:
This is a measure of how precise the instrument is over a repeated measurements in one sitting. It is usually given as a standard deviation over ten measurements. It is fairly easy to test it for a 1mg resolution scale, however, operator skills can influence it on a 0.1mg or greater resolution.

Example: +/- 2mg. This spec is usually +/- 1 to 4 counts of least significant digit (the far right side number... )

Test: zero the scale first. Weigh a coin (the same coin must be used throughout the test) ten times. DO NOT zero the scale during the test.

Take the standard deviation. STDEV=(range of cells) on MS Excel. If it is significantly outside the range, the scale is likely damaged.

Note that this is not a guarantee that if a sample of 10.0000g is weighed, it will read 9.998 to 10.002 EVERY SINGLE TIME. It means that the reading will be within that range 68% of the time. Double the range (in this case, 9.996 to 10.004) for 95% certainty.

Corner load
How the reading varies when the weight is placed off center on a scale. This isn't usually explicitly given, however, using a weight that is approximately half the full capacity of the scale and the reading is off by more than about 10d (10 counts of lowest resolution) the scale is garbage to begin with or it is damaged.

Zero drift:
Digital scales have a tendency to drift a few counts. For this reason, many digital scales will quash out such a drift and return it to zero in the vicity of +/- few counts from zero. Some scales will let you disable this feature in the settings. It maybe called Auto-zero correct, ZeroTrack and the like. If there is no such option, it is possible to disable it by pre-loading on *SOME* scales. Pre-loading means: boot the scale, put a coin or two on it, then zero it. This is a user-set zero and some units' firmware see it different than a start-up zero.

Calibration drift:
How well the scale holds calibration over long term. (weeks, months)

Temperature drift:
How the sensitivity shifts as a funciton of temperature. Usually expressed in PPM.

Selecting a scale:
As shown in the repeatability section of testing, it is not wise to flirt with weighing a sample using the least significant digit even though it may let you disable the automatic zero reset feature.

#1) SWIM dislikes ACCULAB V series (V-xxx, VI-xxx, VIC-xxx). They're comparatively cheap and they comparatively suck! They don't explicitly include many specs, and they tend to suck at those specs. They suck at cornerload and calibration stability. SWIM doesn't have any experience with their high end stuff, like the L, ATL, but SWIM wouldn't buy it.

#2)
Minimum measurement weight needed to keep error within +/- 20% with 95% certainty:
+/- xx mg REPEATABILITY x 10
Equation is derived from
(2 x standard deviation /0.2 =minimum sample weight needed)

Example:
0.1mg resolution with +/- 0.1mg repeatability: 1.0mg
1mg res, +/- 1mg rep (a good 1mg res. scale): 10mg
1mg res, +/- 2mg rep(Acculab VIC-123): 20mg

Note that REPEATABILITY is not the smallest value the display can show. It is a separate spec. It is usually 1-4 times the smallest value the display can show. On a nice scale, this is usually 1. On a cheapo scale, it's a wild guess. It can be 20g x 0.0002g (+/- 0.001g) and still meet the claim that it reads to the nearest 2mg.

If the repeatability spec is NOT given, the scale likely sucks.

For the purpose of measuring RCs, 1mg is the MINIMUM acceptable resolution. 0.1mg is preferable. 0.01mg would be great, but requires greater operator skills and care as the smallest thing will affect the reading. 0.01mg units don't come by very easily and the pricing tends to be prohibitive, so they're outside the scope of this guide.

#3) Don't get a strain gauge scale if SWIY doesn't want a scale that sucks, such as ACCULAB VIC-123. That thing is good for weighing coins, accurate to +/- 2mg, as long as it is calibrated before each use.

#4) A digital scale must have an internal calibration weight or an external calibration weight must be purchased with it. The accuracy of the calibration weight is not that critical.

#5)Used mechanical scales and brand name analytical scales provide a good value if they're not damaged. Fortunately, it is easy to test them. Always buy from a supplier who will take it back if it fails the test unless it's so cheap SWIY is willing to risk it.

Brands:
Yes: Sartorius, Mettler-Toledo, Ohaus, Cahn, Denver Instruments, A&D, or Shimadzu. They're usually Made in Germany, Japan or Switzerland like fine optical and mechanical instruments.

No: Acculab V-xxx, MyWeigh Pro, generic Made-in-China garbage. As much as SWIM dislikes Acculab, it's his opinion that it's the lesser of the crappiness among crappy scales. He predicts their non-V model Acculab won't suck nearly as bad. They're usually Made in China, or assembled in (country name) using "foreign and domestic components".

Calibration weight
For the purpose of weighing out RC in the <50mg range using a balance having a capacity of 60 to 120g, the accuracy of calibration weight is not that important. If the scale calls for 100g weight and it is calibrated with 100.1g, a 10g weight will read 10.01g, 1g 1.001g and so forth. Since even eBay 100g weights are good to 0.01g or so and doesn't cost that much, it should be purchased if internal calibration is not present.

Good weighing practice/methods: (though not in particular order)
1.)Level the scale using the bubble balance on the scale. If there isn't one, well the scale probably sucks to begin with.

2.)Always keep it on. Allow to warm up for at least 15 minutes, or over an hour for 0.1mg balance before calibration or critical weighing.

3.)mg level scales are affected by convection current caused by temperature difference and it will affect the result. Don't use a weighing container that's not at the same tempreature as the scale and don't leave a hand inside the draft chamber forever.

4.) NEVER put chemicals directly on the weighing pan. Use a small weighing dish, a light weight shot glass or the like.

5.) Don't use a weighing paper with 0.1mg or 1mg resolution scales. A heavy grade tinfoil is acceptable for a 1mg scale.

6.) Always use the draft shield.

Reputation Comments on this post:

	Great, great resource for weighing methods
	Great piece- thank you!
	Useful information that is necessary for all research
	Thanks for writing this guide.
	Damn this is a great write-up. Very easy to understand great warnings against cheap imitations.
	Thanks, you supplied great information.

[terrapinzflyer]

Originally Posted by Stimulants

5.) Don't use a weighing paper with 0.1mg or 1mg resolution scales. A heavy grade tinfoil is acceptable for a 1mg scale.

Could swiy elaborate on this more? Are you saying a weighing paper is acceptable with a greater resolution or less resolution scale? What is the min. acceptable weight for a weighing surface with the resolution of scales swiy you mentions?

[Stimulants]

Originally Posted by terrapinzflyer

Could swiy elaborate on this more? Are you saying a weighing paper is acceptable with a greater resolution or less resolution scale? What is the min. acceptable weight for a weighing surface with the resolution of scales swiy you mentions?

SWIM meant weighing paper is acceptable with lower resolution scales. More precisely, SWIM should have used the term "sensitivity".

Anyways, SWIM meant that higher the resolution, the higher the sensitivity

Originally Posted by terrapinzflyer

Could swiy elaborate on this more? Are you saying a weighing paper is acceptable with a greater resolution or less resolution scale?

By "greater resolution" SWIM means greater sensitivity.

Weighing papers should not be used on 0.1mg or greater sensitivity scales

It's fine to use them on 10mg or lower resolution scales without a special care.

a weighing paper often hangs outside the weighing pan. It acts like a wing and amplifies convection current and contributes to errors. A waxed paper is a strong insulator, so it also promotes static electricity.

Analytical scales are VERY sensitive and will respond to smallest influences, which exert real forces, like static electricity and air flow.

On a 10mg scale, these forces are not strong enough to cause a noticeable effect. On a 1mg scale, a reasonable care can reduce the effect good enough to avoid any significant influence.

As this guide is specifically intended for RC weighing, it only covers 3 and 4 decimal place balances.

3 decimal place = 0.001g (1mg)
4 decimal place = 0.0001g (0.1mg)
and so on.

3 or less= precision
4= analytical
5= semi-micro
6 or more = micro

Anything less than 3 is useless for this purpose and anything beyond 4 is uncommon and expensive.

Although, some analytical scales maybe gifted with a dual range and have a 5 decimal place resolution over a limited range, but they're exceptions rather than than the norm. Such an example is Ohaus DV215DC, which is 0.01mg for 0 to 81g and 0.1mg for 81g to 210g

There are a few micro scales with a resolution as high as 7 decimal places, they're beyond the scope of my discussion. They cost five figures (in USD) as well as being exceptionally sensitive to vibration. They require a special installation like a granite table top table on a vibration isolating air bladder.

Vibration sensitivity increases exponentially as the mass of parts used within the scale becomes greater relative to the sensitivity. The acceleration force exhibited on these parts by vibration affects the weighing outcome significantly.

Originally Posted by terrapinzflyer

What is the min. acceptable weight for a weighing surface with the resolution of scales swiy you mentions?

Visitors of this guide may find the repeatability explanation helpful. Because the scale tend to cancel out +/- a few counts, it's safe to avoid playing in this territory ENTIRELY. SWIM would say 10 counts (1mg on a 0.1mg resolution scale) is the minimum sample weight that should even be attempted. On a scale 0.1mg scale with +/- 1 count standard deviation spec, it means that a sample of 1mg would be within +/- 0.1mg(+/- 10% in this case) 68% of the time. Within +/- 0.2mg (+/- 20% in this case) 95% of the time.

If a scale has a 0.1mg resolution, but a repeatability (standard deviation) spec of +/- 0.2mg, then the minimum weight must be DOUBLED to keep the accuracy acceptable.

In SWIMs opinion, it's best to use the 95% figure and assume +/- 20%, which in his opinion is about the maximum deviation that should be acceptable.

On the same scale, by increasing the sample weight to 10mg, the error is reduced to +/- 1% or 2% respectively.

ACCULAB VIC-123
Spec: 120g x 1mg. Standard deviation = +/- 2mg
To remain accurate within +/- 20% for 95% of measurements, then the minimally acceptable weight is:

2 x standard deviation (the 95% confidence formula)
2 x 2mg = +/- 4mg
4mg/20% = 20mg

Therefore, 20mg is the minimum weight it can weigh while maintaining a said accuracy. If the user can accept reducing certainty to 68%, then 10mg can be attempted, though not advised. As easily seen, this scale is inappropriate for use with many RCs and that's assuming that it's working within specs. SWIMs experience with Acculab is that they don't half the time.

Measuring under difficult conditions or using a 0.01mg balance
Attached pictures show a trick to measuring sub milligram level successfully. Static electricity can wreak havoc even inside the draft shield. With 0.01mg(or higher resolution) scales, draft within the draft chamber can cause issues.

1.) Place a small weighing boat on the scale, then tare it. If the reading can not be stabilized, place an inverted metal can on top, then re-zero. The inverted can acts as a much more confined draft shield and as a faraday cage to shield against static electricity.

2.) add the sample. Weighing an unknown amount is always easier than measuring out an exact amount. Shown in picture is a bottle cap weighing boat with a 2mm or so section of a 0.5mm mechanical pencil lead being weighed, which weighed in at 1.33mg

[old hippie 56]

Found a nice and free weighing boat, grab a few of the ketchup holders the next time ya'll in a fast food place. Wax paper works well also.

[Tony Williams]

Originally Posted by Stimulants

4.) NEVER put chemicals directly on the weighing pan. Use a small weighing dish, a light weight shot glass or the like.

Why is this??

[old hippie 56]

Stainless steel pans will make certain chemicals sweat and make it hard to get consistent measurements.

[Stimulants]

Originally Posted by old hippie 56

Stainless steel pans will make certain chemicals sweat and make it hard to get consistent measurements.

No, avoiding cross contamination is the most significant concern.

Originally Posted by Tony Williams

Why is this??

1.) same reason one should not put their food on the public restroom floor, or raw meat on a plate that will be used for serving.

2.) To avoid damage to the scale. Accidental application of excessive pressure on an analytical balance while trying to lift up the chemical that was just weighed can damage the sensor.

3.) How would one pick up a few mg from the weighing pan after the measurement is complete without spilling anything or leaving anything behind?

When a weighing boat is used (even a beer cap works, as shown in my post), all the sample measured can be removed by removing the entire container.

[Blizzard777]

Stimulants, swim would like to thank swiy for the great amount of info he's given us, swim almost bought a shitty scale until he read some great posts on the "rc scale showdown" thread, he never realized how poor the quality of the acculab-123 is, and most electronic scales he's seen in that range

He has looked at the Sartourius ELT-103 as he heard good things and sees that it has a +/- 1 mg readibility and a +/- 3 mg linearity

Would this be good enough for weighing 2c-x compounds such as 2c-i, 2c-e, 2c-c? Say he were to weigh doses 10 mg and above, anywhere from 10-50 mg, would it accurately measure exact doses above 10 mg? (ex. 12 mg, 15 mg, 17 mg)

Furthermore he read in a post somewhere on this site that scales that weigh less than 5 lbs are relatively unstable and the lightweight design makes readings even less accurate, how big of an effect would that have with doses in the range of the above question?

At the moment he would prefer an analytical balance for sure, .1 mg seems like the best option but as discussed earlier obtaining a .1 mg balance on a $400-$500 budget is impossible unless buying from a used source for something like a mettler h6 or h10

He has found a couple seemingly legit online places to obtain the mettler h6 and h10, the prices seem acceptable and he believes they have refund warranties, but in order to buy or inquire from any of these sources it seems he will have to have a phone call with someone from their company...he is wondering if they will even talk to him since he isn't representing a lab or science group whatsoever, just wants one for whatever reason...and in addition these sources all seem to make listing "company" to be a required field on the inquire/order forms

So basically he's asking if it's illegal (or suspicious) to be buying used equipment from lab resale companies and such?

What kind of questions they might ask? What should he say?

Are these watched items?

Also he would call local lab supplies/universities since it would probably increase the chance of the balance surviving transport and be a more trustworthy source but like he said, the above questions need to be answered before he knows if it's even legally safe to talk to these places and what to say

Furthermore these are old machines and although he understands they're reliable how long of life do they really have left? From what he sees these are like 1970's machines, even if they're working today he has to wonder about how much longer they will last even if taken care of properly, he'd hate to spend the money and then have it die 6 months after buying it due to parts not being able to withstand the test of time

And he wonders, say it does break...maybe it's still possible to have it repaired? He is presuming that parts for these mettler models are probably very hard to find nowadays, and probably expensive...PLUS he doesn't know too much about balances or mechanics so he'd have to find someone to repair it, where would he go to get it repaired? If anywhere?

Once again, thanks to Stimulants for all the info and many informative answers

[Stimulants]

Originally Posted by Blizzard777

He has looked at the Sartourius ELT-103 as he heard good things and sees that it has a +/- 1 mg readibility and a +/- 3 mg linearity

Would this be good enough for weighing 2c-x compounds such as 2c-i, 2c-e, 2c-c? Say he were to weigh doses 10 mg and above, anywhere from 10-50 mg, would it accurately measure exact doses above 10 mg? (ex. 12 mg, 15 mg, 17 mg)

The error explanation applies to everything being weighed. Even at 12mg, expect +/- 2mg. +/-2mg at 50mg is obviously less iimpacting than the same at 10mg.

Furthermore he read in a post somewhere on this site that scales that weigh less than 5 lbs are relatively unstable and the lightweight design makes readings even less accurate, how big of an effect would that have with doses in the range of the above question?

This still holds true for 0.1mg analytical balances. The chassis needs to be built well so it remains straight. Add glass doors and such and it will come to at least 5 lbs.

At the moment he would prefer an analytical balance for sure, .1 mg seems like the best option but as discussed earlier obtaining a .1 mg balance on a $400-$500 budget is impossible unless buying from a used source for something like a mettler h6 or h10

He has found a couple seemingly legit online places to obtain the mettler h6 and h10, the prices seem acceptable and he believes they have refund warranties, but in order to buy or inquire from any of these sources it seems he will have to have a phone call with someone from their company...he is wondering if they will even talk to him since he isn't representing a lab or science group whatsoever, just wants one for whatever reason...and in addition these sources all seem to make listing "company" to be a required field on the inquire/order forms

So basically he's asking if it's illegal (or suspicious) to be buying used equipment from lab resale companies and such?

In the U.S. they're not. They're used for many different things. i.e. checking lubricant efficiency. Lubricate bearings with lubricant A, vs lubricant B. Degrease them both. How much metal did they lose and which lubricant was more effective in reducing wear?

They're also used quite often to measure very expensive jewelry, such as diamond.

What kind of questions they might ask? What should he say?

Are these watched items?

SWIM isn't sure.
No, not really watched.

Furthermore these are old machines and although he understands they're reliable how long of life do they really have left? From what he sees these are like 1970's machines, even if they're working today he has to wonder about how much longer they will last even if taken care of properly, he'd hate to spend the money and then have it die 6 months after buying it due to parts not being able to withstand the test of time

Should last years after years, unless abused. Since abuse and accidents are not covered under warranty even with a new unit and a repair would cost more than a few hundred dollars, there's not much to lose. Parts are generally not available except for authorized repair shops even on new models and that means paying someone to fix it.

And he wonders, say it does break...maybe it's still possible to have it repaired? He is presuming that parts for these mettler models are probably very hard to find nowadays, and probably expensive...PLUS he doesn't know too much about balances or mechanics so he'd have to find someone to repair it, where would he go to get it repaired? If anywhere?

Once again, thanks to Stimulants for all the info and many informative answers

Repair is not cheap, regardless of how old it is. Mechanical balance isn't likely to "break" unless there's a user error involved, which would be considered accident and not covered by any warranty anyways.

[RaverHippie]

found an old mechanical balance on an auction site and the seller was adamant about how difficult it would be to ship the item and that it would take a large amount of effort and money so that any buyers should warned. Complete care was shown in his words. This particular balance is said to be accurate at the .05mg level and would be measuring quantities 1mg and larger. I feel like this may be a fun collector item and a steal. Is Christian Becker a noted company?

Thanks again for the write-up, I've read this thread 4 or 5 times as I've been searching for a measuring device.

[old hippie 56]

Did it look like this one. If so, cowboy got beat on a auction for one similar. Heard they worked good, kinda belongs in a museum instead of a lab.

[RaverHippie]

Originally Posted by old hippie 56

Did it look like this one. If so, cowboy got beat on a auction for one similar. Heard they worked good, kinda belongs in a museum instead of a lab.

yeah it does have that appearance. The item description said that it sat around a store for 20 odd years so I thought of a used car analogy, it was like a muscle car sitting in a barn somewhere. No money invested yet.

[Stimulants]

Originally Posted by RaverHippie

found an old mechanical balance on an auction site and the seller was adamant about how difficult it would be to ship the item and that it would take a large amount of effort and money so that any buyers should warned. Complete care was shown in his words. This particular balance is said to be accurate at the .05mg level and would be measuring quantities 1mg and larger. I feel like this may be a fun collector item and a steal. Is Christian Becker a noted company?

Thanks again for the write-up, I've read this thread 4 or 5 times as I've been searching for a measuring device.

The photo posted by O.H. is an even older type. The one that is really desirable is the mechanical substitution type, which is a single pan and it is extremely easy to use compared to two pan balances and weight sets are not needed.

The pressure on knife edge remains the same, because it is always under full load when in use. To measure 112.5523g: 100g, 10g and 2g counterweights are removed and the weight of the sample substitutes it. The remaining 55.23mg is tuned using the fine reading knob.

The balance should be "arrested" whenever something is put on, being transported or not in use. It should be semi-arrested while operating the course knobs. Finally, the beam should be put down to make the fine tweaking.

The heart of the mechanical balance is the knife edge, which is usually made of synthetic sapphire. It is very sharp, hard and fragile. If it's been moved around without arresting the beam (using the lever to raise the beam and taping the lever so that it does not move) it's gone. The knife edge replacement or personnel skilled to replace it are probably no longer available.

It's best to find one at a university surplus or such where the item can be inspected in person. The only test needed is weigh a nickel four or five times and verify that it comes back to the same reading each time.

It's best to read the manual ahead of time to get a basic idea of how to use it. Manuals are available by searching the web for "mechanical analytical balance"

Taring complication can be avoided by using the same shot glass for weighing container and have it written down. A good mechanical balance does not lose calibration like electronic scales. They're actually much costlier to use than electronic scales.

Electronic scales are great for research/commercial labs where time is money. They need calibration so often that new ones have a calibration weight built-in to the scale and motorized servo automatically calibrates it on regular basis.

[RaverHippie]

Okay that does seem easier to operate and make multiple measurements.

attached is what ebay is teasing me with. 0.05mg readability for the price of an acculab.

[Stimulants]

Although SWIM isn't totally sure what the knobs do on that scale, it appears to be a two panned, traditional balance that requires precision weights and has a very steep learning curve.

i.e. when weighing 1mg on 10g container vs 1mg on 50g container, it's necessary to pre-load both sides of the balance.

So for the first example 2x20g on both sides. 1x10g on countering side.
Once the balance is balanced, the sample of 1mg can finally be added, then 1mg mass added to the counter side until it is balanced again.

For the second example 50g container is placed, then balanced with 50g of counterweights. Sample is added, then measured using a 1mg counterweight.


The bearings don't behave the same at no load vs full load. Single pan substitution balance does this automatically so the bearings are always placed under same load.

SWIM would not get a two-pan balance.

In order of his preference for 4 decimal place scale:
Mechanical substitution (Like Mettler H6)
Electronic (Pretty much all that's available new these days)
Two pan (these are hard to use. Precision weight sets are very delicate and very expensive)

[researchbishop]

SWIM has a cheap and rubbish set of scales which was fine Meph, but wanting to try the 2CX family. SWIM know betters scales are required, and has found these ProScale Gemological 50 are these totally useless for purpose?


Details here:
# 10 gram/50 carat capacity
# 0.001gram/0.005 carat readability
# Reads in Grams, Carats, Pennyweight & Ounce
# Auto Calibration (weights supplied)
# Energy Saving Auto-Off Feature
# Built-in Add-Up feature
# Powered by 4 x AAA batteries (not supplied)
# Gemstone Tweezers, Wind-Screen, Calibration Weights and Carrying Case ALL Included
# Ultra Low Cost
# 5 Year Warranty.

[Stimulants]

Originally Posted by researchbishop

SWIM has a cheap and rubbish set of scales which was fine Meph, but wanting to try the 2CX family. SWIM know betters scales are required, and has found these ProScale Gemological 50 are these totally useless for purpose?


Details here:
# 10 gram/50 carat capacity
# 0.001gram/0.005 carat readability
# Reads in Grams, Carats, Pennyweight & Ounce
# Auto Calibration (weights supplied)
# Energy Saving Auto-Off Feature
# Built-in Add-Up feature
# Powered by 4 x AAA batteries (not supplied)
# Gemstone Tweezers, Wind-Screen, Calibration Weights and Carrying Case ALL Included
# Ultra Low Cost
# 5 Year Warranty.

Who knows. The screen reads in 1mg increments. That's all that is known. Neither repeatability nor accuracy is known, so uncertainty is unpredictable.

[old hippie 56]

Cowboy had a set of these once, they worked fine for few months, then something weird happen to them. Using different calibration weights, they would show +/-.05, on the set that came with the scales it was right on. Borrowed some weights from a buddy, still showing the same thing. They been retired.

[researchbishop]

So ProScale Gemological 50 rubbish then.

Anyone recommend a set with 0.001g

[Stimulants]

Originally Posted by old hippie 56

Cowboy had a set of these once, they worked fine for few months, then something weird happen to them. Using different calibration weights, they would show +/-.05, on the set that came with the scales it was right on. Borrowed some weights from a buddy, still showing the same thing. They been retired.

SWIM does not quite get the clear picture.

Originally Posted by researchbishop

So ProScale Gemological 50 rubbish then.

Anyone recommend a set with 0.001g

Mettler-Toledo or Sartorius. German or Swiss made.

[researchbishop]

Originally Posted by Stimulants

Mettler-Toledo or Sartorius. German or Swiss made.

SWIM would love anything made by either these people but, for 1mg readable scale you are talking £1000 and up.

The problem faced is that the scales SWIM mentioned in the first instance ie the ProScale Gemological 50, which can be picked up for about £45, okay nice and cheap yes, reliable unlikely, so more money could/ should be spent, but the next scales that seem good are either:

Acculab VIC-123 approx. £260
Ohaus Scout Pro approx. £285

This is a huge leap, just can not find a mid-range set between the two.

Purchase to be made from the UK, which makes it all the more annoying to repeatedly see the Acculab VIC-123 available for approx. $200, which would be around £120, so maddening.

Are the above two, namely:
Acculab VIC-123 approx. £260
Ohaus Scout Pro
Up to standard?

Or can someone advice the model name of something for about £150.

Thanks

[Stimulants]

The balance does not need to be bought brand new. The test procedure given should let you identify damaged units.

Ohaus is a subsidiary of Mettler-Toledo and their post-acquisition scales often use Mettler-Toledo parts and they're usually good.

Good 1mg or higher resolution scales use a magnetic force restoration sensor, which gives far more consistent results. Cheap ones with very little dynamic range (i.e. 1mg x 10g is only 10,000 counts) is based on a strain gauge.

Strain gauges are typically used for kitchen, road truck, and bathroom scales.

Mechanical substitution types often come from university surplus, because chemistry program does not like to have to devote a lab session or two just on how to operate the scale. They buy digital units to get around this.

[researchbishop]

SWIM would like to thank everyone for their help with the scales, especially Stimulants, who is lord of scales.

SWIM is going to wait until a purchase of 2CX chemicals is made probably a month or two, then buy the Ohaus Scout Pro, presuming nothing better, for the money, suddenly appears from nowhere, seems unlikely.

Also as SWIM has been reading about plugging, and feels this is definitely the way forward, and as dosages are even lower, the increase in required accuracy is greater.

Thanks

[RaverHippie]

My raver friend may have lucked out. He found a used Mettler AE200 scale. It should come in tomorrow upon which the accuracy procedure for used scales will be tried. Thanks again for all the help.

[Stimulants]

Mettler AE200 is one of the best back in the days and if it is in good conditions, it should be just as good as a new one even though it would not have any features beyond taring and displaying the current weight.

The newer models just adds automatic calibration, multiple units, and etc.

On the AE, it is possible to change the integration time by holding down the bar until it shows INT then tapping the bar to choose 1, 2 or 3 with 1 being the fastest response, 3 being the most accurate (but very slow) update.