Testing cheap ebay calibration weights.

I looked on ebay for a calibration weight to test my scales for accuracy, and found a set of 5 weights that could be used in multiples to create a wide variety of weights from 5g to 105g. I bought a set expecting them to be a bit random, but when tested on different scales they do seem to be very accurate.

[@Aboutji]

Always good to see something from ebay that's not going to kill me if I use it.

[@DevReaper]

They still could be toxic

[@pierreuntel1970]

Maybe they made from waste plutonium?

[@de6hl]

Lead poisoning

[@MrBanzoid]

I once used a lab balance that was so sensitive that you could weigh your name! You weighed a bit of paper then signed your name with a Sharpie, pop it back on the balance and you could see the weight of the ink and watch the weight go down as the solvent evaporated. Not really useful for me as I generally did "Bucket Chemistry". It's interesting (to me anyway) to note that really sensitive balances respond to variations in the local value of G (the force of gravity) so they should be calibrated where you're going to use them on Earth. Objects will weigh less on top of a mountain although the difference is tiny. Useless fact while I'm here:- most cheap balances use the compression of a spring to measure the weight of an object while more expensive ones use magnetic repulsion and measure the current needed to lift the object, something like a speaker cone. Another useless fact. A spring or magnetic balance measures the weight of something. Old fashioned scales where you have the object on one side and known weights on the other side actually measure the mass. For example, if you use a spring type balance to measure something on Earth and it weighs say 60 grams, on the Moon it will only weigh 10 grams because gravity on the Moon is only one sixth of what it is on Earth. However if you weigh the same thing on the Moon on a traditional set of scales you will need 60 grams on the other side to make it balance. Balances that use springs or magnetic repulsion measure WEIGHT, that is, the effect of gravity on an object. Scales measure the MASS i.e. the amount of matter or stuff in an object. For all intents and purposes weight is the same as mass unless you're on the Moon. It's easier to say "weigh" something than it is to say "determine the mass of something" which my old physics lecturer used to say in his pedantic manner. OMG here I am rambling on again - sorry.

[@Hopeless_and_Forlorn]

+MrBanzoid Even more useless fact: back in the day, I was shown an aircraft instrument repair shop, and stopped to look at a mercury column used as a master instrument to calibrate test equipment for altimeters and other instruments. The assembly around the column was more complex than I expected, and I finally made out that one the scales on it allowed adjustment for the local force of gravity. I could not imagine how tiny changes in gravity could affect an altimeter, until I realized that the weight of the mercury column, not its mass, determined its height in the tube when subjected to a given pressure differential. If gravity in a given place was lower than another, the column would be higher, and higher gravity moved the column down. Since the shop in question was located at 5300 feet above sea level (Denver), the difference in local gravity compared to sea level could be enough to affect the calibration of the column. The technicians in the shop seemed to think that every dummy should know that, but I did not.

[@tybo09]

+Hopelessand Forlorn I used to use one of those style barometers in college. We had it at our weather station, but every so often, folks from the physics and chemistry departments would come over and use it as a check on their (much more expensive and technologically advanced) equipment.

[@a133m210]

I had to fill in a parking permit application that asked for the weight of the vehicle I was adding. Was reminded of my physics teacher too. Was tempted to give them a weight in Newtons and specify a location, height above mean sea level

[@floobertuber]

+MrBanzoid - I'd say those facts were ANYTHING but useless. You taught me a couple of new things today!

[@thesunexpress]

I measured the weight of my breath while at university... for giggles we had one of our hung-over functional-alcoholic friends do the same: the average ratio of his breath actually weighed more, to our bemused surprise. 'T was Thursday afternoon though, at our school we generally had no classes on Fridays, so we didn't stick around to geek out in a chem-303 fashion to gas-chroma his breath to figure out wtf was causing the increase. G-n-T's, Tribe Called Quest, making fun of the electrical engineering students (can't spell gEEk without a double E), physics nerding & badgering TKE frat-bois at night was upon us.

[@Tocsin-Bang]

I remember many moons ago that my secretary in the lab where I worked suspected her packet of crisps (potato chips) were underweight. I weighed them on a laboratory balance to 1 milligram accuracy. She sent the result to the supplier. When she got home a few days later she couldn't get through her front door for boxes of savoury snacks!

[@sveindanielsolvenus]

The last part of your cool story is called "silencing the witness".

[@revemb4653]

@@sveindanielsolvenusI too am in this comment section

[@Smoke1]

...they're ideal for weighing small quantities of "chemicals"...

[@SmokeyDaRoach]

I read the title as 'Celebration Weights'. I got pretty excited.

[@AdityaMehendale]

9.98 + 19.98 + 19.99 + 49.99 = 99.94 At 1:35, it "adds up" to 100.03 I'd say the masses are darn good; it is your scales that have a teensy negative offset...

[@nomiserah]

+Aditya Mehendale There are inaccuracies with both the weight and the scales, more so the scales i'd say. The scales are non linear up their range, the weights differ too especially on the 20g, but that may be a repeatability issue or corner error with the cheap balance (most probably). I used to use F1 weights to calibrate down to 6 dp's after the point in grams, now that's accurate, but not compared to the Kilo standard set in France! :)

[@owenattard1467]

+Aditya Mehendale Hmmm.. it may also depend on where you locate the weights on the pan. I am pretty sure that if you place weights on the edges, you will get shifting in measurements. At the same time, the factor of rounding the number to +/- 0.01 g may also have an impact on the final result.

[@johndododoe1411]

@@nomiserah That reference recently stopped being the definition, but they somehow snuck in new definitions for several other base units into the same vote.

[@samuellourenco1050]

Although ADCs and op-amps have offsets and deviations, these issues are solved in scales by taring and calibration, respectively. I would say that the weights are deviated, and probably it is an issue with the calibration machine that was used to calibrate them.

[@Clip7heApex]

I use a set of those scales to weigh my air rifle pellets. A tin of pellets can have quite a bit of variation between the pellet weights, which affects the accuracy significantly over 40 yards. Probably only get about a quater of the tin close enough for when I do competitions.

[@68MalKontent]

High resolution is easy to attain, but linearity and repeatability make the resolution useful, otherwise we're basically seeing noise on the least significant digits. This little scale shows amazing linearity for such a cheap product.

[@wupme]

+68Stan mine was about 30 bucks, so actually almost high price lol, but its really accurate. It came with calibration weights (2x100g) and i also have a 200g and a 500g i bought some years ago. The scale is precise to around 0.005g across the board. And i also checked the weights with a calibrated scale from an apothecary, who where nice enough to let me check my scale and weights :) But well, 0,2g would also have been good enough for me. I use it to measure small amounts of spices for recipes so i can create spice mixes on a larger scale.

[@PashaSiraja]

that middle one's great for weighing charlie!

[@thomasbjrkhaug6387]

Interesting. I work at a snacks factory and sometimes when weighing up the salt and oil samples on scales that has an accuracy of 0.001 grams we have to turn the ac off due to the movements in the air causing drift. And these have walls to stop the air.

[@JamesSleeman]

If you look up the specifications for your locale's coin currency you should be able to find the weight of each, and it's quite closely controlled. I've used that to check my "precision" scales from ebay. Here's the Royal Mint's coinage specifications: www.royalmint.com/discover/uk-coins/coin-design-and-specifications

[@technodaz]

James Sleeman Depends on how accurate you want your calibration , coins should be real clean and not worn , I played around at work once in a bio-chem lab and had a half day toying with a +/- 4 µg micro balance and you be very surprised not only how much they vary , even clean coins. And once you start using multiple sets of different coins it really starts to add up. For 0.00g scales makes little difference but depends on what your weighing , we had some chemicals that cost a small fortune per gram and trust me you want a accurate scales when your only putting a few mg in a batch of plant food. But yea for every day use , ill still use euro coins.

[@Doazic]

Ask for change at a bank. Fresh out of the bank coins should be pretty much perfect.

[@IIGrayfoxII]

+Doazic Not all banks give you newly minted coins, they will give you what they have which is what other people have deposited in. Only badly damaged ones get scraped. Small nicks, dints wont make them toss them.

[@Doazic]

Well sure that's a fair caveat but the wrapped up packages of coins are usually mint condition.

[@johndododoe1411]

@@Doazic Nah, they have packing machines to wrap counted coins as they receive and supply change to shops. Wrapped packs often contain an assortment of minting years, as coins are expected to have a long average life.

[@scottgray6276]

I couldn’t imagine why you had a sample card of snaps!?! I had one of those tiny scales in the dye room…it was good, down to.001grams, it claimed, and seemed to be pretty accurate, until the battery got low! Fortunately, the reading it gave then were so ridiculous, it was obvious it needed new batteries!

[@donald6815]

The Chinese are making some high quality, reliable, low cost stuff. Also some junk.

[@LawrenceTimme]

obvious dealer scales.

[@wupme]

+Lawrence Timme i think we have to thank drug dealers for making those scales being available for so small amounts of money :)

[@LeifNelandDk]

What drives innovation seems to be sex (porn), war and drugs :-(

[@TheActionBastard]

@@LeifNelandDk - really only one of those sounds like a "bad" thing. The others sound misunderstood, misused, and poorly explained to people with honest, factual science.

[@LeifNelandDk]

@@TheActionBastard , and everything fun is either illegal, immoral or fattening.

[@johndododoe1411]

@@TheActionBastard Benefits of all 3 are easily explained without science. The main sciences to sway their goodness are philosophy, theology and statistics. But rhetoric is frequently the more expedient choice.

[@david_pilling]

There's the thing about measuring 100 sheets of paper and then 1, by division you can get an accurate tiny weight. Probably works with 100 2N3906's. Some scales have a combination of buttons to press to enter calibration mode.

[@user-gx6jb6wc5g]

David Pilling My mini set has a calibration mode for a 200g reference weight.

[@OAleathaO]

Glad the Post Office in the UK cares enough to keep their scales accurate. The US Post Office near me is usually off 2-4oz. I swear they know it too because whenever I argue the point they always make a manual correction. However I usually only argue the point when I know my package is 13oz or less (max weight for 1st Class Packages) and they try to charge me Standard Post rates.

[@Heizenberg32]

Of course, the Post Office! I wanted to check the calibration of my old, relatively cheap, scale but couldn't think of somewhere that would have a good one.

[@mfx1]

I took one along to an NPL open day some years back and stuck it on one of their precision scales and while I can't exactly remember the accuracy it was surprisingly good.

[@arapigny9885]

that is pretty neat but clivey you know we like to see all the scale numbers

[@topilinkala1594]

About scales: Think how you make a scale that can measure from 100g to 20kg with 50g accuracy but at the same time withstand 200kg? Those were the scales we had in international mail in Finland. The international agreement was that air mail would measured from 100g up to the maximum of 20kg with accuracy of 50g. But as practical safeguard Finland Post understood that everyone would like to weight themselves on these scales because as airmail bag scales they were big enough to a human stand on them. There was only one scale manufacture in Finland which could make those and there were not cheap. But consindering to ask someone to come and calibrate your scale because it was used to weight a human was even more costly. This was in 90's. Don't know what it is now as the airmail moves not in bags but in receptacles.

[@chrism2964]

Even in a lab environment we dont always have to worry about absolute accuracy as much as linearity, as in the ability to be accurate and similarly accurate, throughout the scales range. If a scale is 1% out then its not so bad as long as its 1% out all the time, and consistently 1% out (so always over for example). That way everything you weigh on it will be in proportion. What you dont want is something 1% under at 10g and 1% over at 100g. If you check a scale at the top, middle and bottom of its range it needs to be consistent, if it varies wildly in the middle its also no good.

[@davidmg1925]

Nice video. Love that counting idea.

[@LC-yn2xt]

They probably grind the tip of the screw and the housings are lightweight and standardized.

[@thesunexpress]

It is important to note the local gravitational field, distance from the equator etc... these all impact the total weight read; particularly when dealing with the very very tiny weights. From experience: being off by 0.1 to 0.01 to 0.001 factor is easily caused by latitude. There's a video floating around on KZbin of a private jet pilot / turbo-nerd, who took a 500g calibration weight & measured the change in apparent weight whilst flying East West. I forget the exact figure but it was a difference of around 10 grams or so.

[@mikapirinen5561]

You must recalibrate ebay scale, pressing unit button with power button on (text "CAL") and then again unit button (text "CAL" blinking moment and ask calibrate weight). Then put scale max weight 200g or 500g and when pass text appear, scale is calibrated. Used buttons can vary.

[@caskwith]

Interesting. My set of "jewellers" scales, very similar to your own set there, actually came with a set of 2x 50g high accuracy weights so you can calibrate the scale and re-set the load cell. Never bothered other than the first time I used it since I rarely need that much accuracy, nice thing to have though.

[@DoctorX17]

I think the reason you're not supposed to touch them isn't because your greasy fingerprints add weight; it's because contamination from your skin can potentially cause corrosion, and that can lead to loss of mass over time. Altho I don't know if there's any practical loss of mass for the level of accuracy a user looking for cheap calibration weights would need to be concerned about, it probably is going to be an impact in the 3 or 4 decimal range if I had to guess [I don't think most folks are worried about their scales being like 0.0007g off]

[@expierreiment]

You said the scales are very accurate. But how do you know without a officially calibrated reference weight. Accurcy is the term for the deviation of the displayed value to the certified value of the reference weight.

[@eddiebernays514]

I worked at a headshop (smoke shop for bongs) and sold tons of these weights. they were pretty good, the scales weren't very good. they could be uncalibrated just by moving it.

[@jordandurham8951]

They're usually calibrated with lead

[@whatevernamegoeshere3644]

"5.02. Hm, that is very accurate!" Meanwhile I get scolded over a 100μg mistake at the analitical lab practice lol

[@G56AG]

A lot of those cheap scales aren't very accurate, and I wouldn't trust check weights I bought off Ebay, they might be accurate and they might not, and weights from different sets from the same manufacturer can vary widely. A very general rule of thumb for accuracy, it doesn't make any difference how many decimal places it has, and in general those little flat scales like the one in the middle aren't very accurate, the drifting you had during the video is evidence of that. Generally speaking, the accuracy of check weights is very closely tied to how much money you pay, its very educational to look at the allowable tolerances of different check weights according to the ASTM or one of the other testing standards, BTW precision weights should never be touched by bare hands.

[@Tocsin-Bang]

Inside there is a hollow space, they add tiny amounts of ?lead to adjust them.

[@ElectronPower]

Hi, Clive! A few months ago, I bought one of those cheap "drug dealer" scales from ebay, for about 10USD and I was amazed how accurate it was (I tested it with 500g calibration weight) and the scale measured it to be 500.01 or 500.02g (I don't remember exactly). However, the problem is, that it only works for a few minutes after you put the batteries in, then you have to take batteries out and wait for pretty long time, before putting them back in, in order for it to work again... Even shorting out the terminals on the scale, doesn't help, with making that "waiting process" faster. Do you know, what could be wrong? Any simple way to repair that? I opened it and unfortunately found, that the chip was covered with that epoxy type of thing... Thanks! Best regards, Electron PS: nice video, thumbs up!

[@user-gx6jb6wc5g]

I'm not sure what's happening there. Are the batteries fresh?

[@ElectronPower]

+bigclivedotcom Hi, thanks for response! Yes, I've tried a few times with completely new batteries. Yes, it's really strange, I just can't figure out, what it could be... Best regards!

[@user-gx6jb6wc5g]

+Electron Power I had a similar thing happen with two sets of Salter kitchen scales. They would work fine until one day the only way to turn them on was to remove and re-insert the lithium cell. Changing the cell for a new one didn't solve the problem.

[@ElectronPower]

+bigclivedotcom Yeah, really strange problem. I wish I could solve it somehow, but don't even know what would be the reason. maybe there is some capacitor, that needs to be discharged for some reason, before I can reinsert the batteries and turn it on again.

[@MrTectu]

+Electron Power For personal interests: Can you link to the one you actually bought?

[@ckwunch8028]

Ebay itself is a brilliant website, its just the quality "some" individuals put on there that gives it issues.

[@Number12lookslikejoe]

Just put a 1 pence piece on the scales, and if it flickers between 3.5/3.6....or comes up 3.56 if you have double digit scales...your good!

[@stephenlamley541]

Thats how decent calibration weights come, i worked in fords foundry Leamington spa. It was more my dads job ghat used them he tested sand so the cores dont split when being knocked out. At that time by a deezer matic line. Not spelt correct. Got a obscure German spelling.

[@RLingate]

I have calibrated my scale (max. weight 100g and 0.01g precision) with water. I have a bulb pipette and when the room is 25°C (298K) a volume of 10mL weights 9.98g

[@johndododoe1411]

Ah, the original definition as 1g = 1cm³ of water of some description. Still wonder why they didn't revive that for the recent reform, specifying isotope ratios for reference water and declaring any deviation as a source of measurement error in reproducing the standard.

[@samuellourenco1050]

However, how you can be sure if you are really measuring 10mL with an uncertainty within 0.1% (which is probably too much uncertainty for calibration)?

[@Thermalions]

Royal Mail's super accurate scales - if there anything like Australia Posts then they may have been super accurate when they were new, but how often do you think they are really properly re-calibrated (in practice, not just based on the manual)?

[@snoopdogie187]

Well in the US, I think its once a year. I manage a deli, and we have a certified scale for selling food by weight, and the state official comes once a year to check the scales and make repairs if needed. I think the post office has to follow the same rules since they are also using the scales to sell something by weight, although in their case, it is service, instead of a physical item. I also think I see the sticker that the state official leaves on the post office scales.

[@okaro6595]

+snoopdogie187 Once a year is very seldom if you do not check it yourself once a while

[@snoopdogie187]

***** Well in the 5 years we had those scales, accuracy to 0.01 pounds, they never once have been off. One is over 20 years old, the other seems to be a cheap Chinese knock off.

[@bilkyasko]

In my experience, if you have to have your scales calibrated (in the UK), the calibration certificate is usually valid for a year. The certificate shows what adjustments were made, which should give you an idea of how potentially inaccurate they could become after a year.

[@bulwinkle]

Hmmm. If we are talking metric units grammes are an SI unit of mass and not weight which is measured in Newtons, but heigh-ho.

[@theguy9208]

+Robert Langford oh relax with that pedantry. lol

[@dopiaza2006]

+Robert Langford Actually kilogramme is the SI unit of mass, which is kind of odd as it's a multiple.

[@bulwinkle]

I agree. It is odd.

[@bulwinkle]

+Robert Langford I also think that, if you check for yourself, you'll find that the gramme/gram is also an SI unit.

[@dopiaza2006]

+Robert Langford Yes, but gram is not a base unit - it's a derivative. Which makes it even odder!

[@HifiCentret]

With those scales you can't really verify the weights. Beside I find most scales - event the 0,01 gram resolution ones are not the best. Of 4 such scales I got only 1 reliably reproduce the same results. Funny enough it's a cheap cigarette themed scale, Marlboro (not Manlloro), from a Chinese gadget site. On that scale all my calibration weights are dead on - after calibration. 5, 10, 50, 100, 200 grams all perfectly dot-zero-zero - even the Banggod and DX weights. Such scales need calibration form time to time as they will drift with time - the most right after manufacture. Kitchen scales are generally not that great so those you got there are great. So yeah. Either all my weights are off by same percentage or they're actually quite good. More than good enough for .01 gram scales for private use. Another great scale I got is a Kern 440-47N I dumbster dived. "Only" a 0.1 gram (2000g max) but it just gives a quality impression. I have two cheap 500g weights (2x 1000g) sets on the way so I can calibrate it properly. It can use 500, 1000, 1500 and 2000 gram for calibration. I have calibrated it using 500 gram and many(!) chinese weights but I want it a little better. 1000g weight I have trouble finding great ones at reasonable price and even more so 2000 gram - if they're to be shipped so for the moment I'm settling for 2x 500 which should be more than adecate for a 0.1 gram scale at halfway calibration. There was of course a reason it was thrown out. The 9v battery clip had become broken and battery door had become missing a long time ago (lots of tape residue). It got a thorough clean, a new battery clip and I made a new battery door - if not as good as new it's very close. And it's not exactly a cheap scale - definitely one of my better dumpster finds.

[@chrisrobinson8247]

depends where you are in the world according to wiki. I.e. gravity difference plus dust particles also air contamination causing chemical film, nicotine would be one, exhaust fumes too. Makes it easier for our dealers to stuff us :p

[@Neighbour_Al]

Precision and accuracy are not the same thing.

[@Berkeloid0]

You'd hardly describe something as precise though if it was completely inaccurate :-)

[@SeanBZA]

Should have come with a cal certificate as well, telling you with some degree of accuracy the actual mass, and preferably traceable to a standard kilogram somewhere. My ones have the cal cert, telling me to within 1ng on the small ones and to 4 figures in all cases the mass. Verified by a cal lab as well. How much did the set cost, I might buy a second one to compare ( have the mass meters to verify them to mg level) and then have a spare set to use when one lot is off to cal.

[@RobertSzasz]

These are cheap sets. Sets with real certs cost a lot more.(10 verses 100 dollars)

[@SeanBZA]

Robert Szasz Ordered a set, will do a verification of them against my calibrated set when they arrive. They were cheap enough as a set of 6. Wonder just how close they will be to the printed value.

[@RobertSzasz]

I'd assume better than 1 percent accuracy in all but the cheapest sets.

[@SeanBZA]

Robert Szasz I can measure to an order of magnitude better than that so will see when they arrive. just will have to leave the precision balance on for a day or two to stabilise to 5 digits. We rarely use it as we rarely need the precision, but it is there, and most of the others have at least 2 units that cover the desired ranges. Can be a little expensive come verification time, as they are all done in situ.

[@samuellourenco1050]

The weights are not accurate at all. The 10g is out by 0.2%, the 20g one is out by 0.1%, and the 50g is out by 0.02%. Only the 50g one can be considered an M3 class weight, which should have a tolerance within 0.05%. Mind that the M3 class is the least accurate class that can be used for calibration.

[@terryhayward7905]

You will get arrested as a drug dealer with one of those scales, be careful Clive :)

[@kaanankaanan1850]

your camera and your other scale could cause scale drift

[@nicktohzyu]

but how accurate is that scale?

[@datinniezaidi7754]

Guys,beware these cal.weights may contains Capazitorz! Chinese........

[@TheChipmunk2008]

I too have found those kitchen scales to be fairly accurate, same reasoning too, royal mail's scales on postage Must get a set, guess i'll search fleabay for calibration weights :)

[@user-gx6jb6wc5g]

***** Not that it really matters so much these days since they decided to set the first price point at 0-100g. Quite a massive postal cost jump for me, since most of my kits or chips weighed between 12 and 60 grams.

[@superdau]

***** Same here, just not the royal mail ;) . I really didn't know what to think of these cheap kitchen scales (bought one for 11€ at Aldi/Hofer ; the discounter from Germany/Austria if you know the name). But after I weighed a 2,5kg package and the post office showed just 1g more (you could argue it was even dead on, because I hadn't taped the parcel yet when I weighed it), I think they are well worth the money.

[@ramonatan4406]

That's shit..what if I want to weigh up wraps of crack at 0.2 a bag and they are 0.1 /0.2 out

[@massivewangman]

your getting precision and accuracy mixed up

[@habiks]

The problem seems to be in cheap weight scales, not the weights..

[@flagpoleeip]

your accurate scales are for weighing drugs.

[@Anvilshock]

And bread was eaten by Hitler!

[@whatevernamegoeshere3644]

I bought them in a boundle with 200 ziplock bags :3

[@TheActionBastard]

And airgun pellets... and gunpowder... and chemicals/compounds for chemistry or science experiments or research... the list goes on. Funny how the only context you mention is drugs. ;)

[@peterzingler6221]

Normaly drug dealers use coins to try there scales out