I was watching the above programme on TV on Saturday (nursing a hangover) and noted that all the measures were in imperial except for one.

The UK presenter said something like "We all like a game of cricket but lets go over to our American colleagues for an attempt on a strange record over there..."

We then cut to the US studio where two chaps were about to perform the worlds greatest cricket spitting distance (do they really do this in America?)

Anyhow - although the distance was in feet and inches they started off by saying that each cricket had to weigh 5 grammes and showed each one being weighed on a scale in such a way.

I found that a little ironic in relation to our conversations here (although no doubt the audience couldn't give two hoots).

I was wondering, though, if this series was shown in SA, NZ or Australia - and if so whether they translate into metric or leave "as-is".

Anyone know?

<<We then cut to the US studio where two chaps were about to perform the worlds greatest cricket spitting distance (do they really do this in America?)>>

The Guiness Book of Records is full of obscure people doing obscure things most of us wouldn't think to do. Much less competition for setting a record that way. I certainly plan to leave their record unchallenged. :)

The various apothecary measures less than 1 ounce are virtually unknown here except maybe for the grain, common in loading ammunition. The grain used to be used a lot in OTC pharmaceuticals too, like 5 grain aspirin. Probably much easier to find a gram scale for such small amounts.

Fair enough - I thought they might use n'th of an ounce or something.

I agree that for something so light a gramme would be best.

"The grain used to be used a lot in OTC pharmaceuticals too, like 5 grain aspirin"

I can't ever remember seeing grains used for aspirin. Even as a child they were always listed in milligrams. 325 mg is common on some brands like Bayer, but Anacin has a 400 mg dosage.

http://www.vitacost.com/AnacinPainReliever

If I have a real bad headache, which I don't get too often, I can either take two Anacins if they are available of 3 of the other brands that only have a 325 mg dosage. None of the non-aspirin pain relievers work at all for me.

<<I can't ever remember seeing grains used for aspirin. Even as a child they were always listed in milligrams. 325 mg is common on some brands like Bayer,>>

I can, which probably only proves I'm older. Within modest rounding, 325 mg is 5 grains.

re (Stimpy): "I agree that for something so light a gramme would be best..."

REPLY: There are 16 drams to an ounce which is fine. And of course there are 7,000 grains to an ounce.

On page 7 of the now-legendary Customary Measures Society's "Weights and Measures: Britiain's Way Ahead" is a full colour picture of an article from the Whitby Gazette in 2003 titled: "Champion gooseberry sets record".

This extract from that report follows:

"It was a proud moment for grower Geoff Bielby, of Thirsk, who smashed the show record with a yellow woodpecker [variety of gooseberry] weighing 33 drams and 21 grains - more than two ounces"

<<REPLY: There are 16 drams to an ounce which is fine. And of course there are 7,000 grains to an ounce.>>

Actually, there are 7000 grains to 1 av lb, 437.5 to an ounce.
I don't know what a dram is; I don't think they have been used much in the US. So the cricket must be > 77.16 grains, approximately.

Thanks to Tony for bringing us an example that shows the imperial system at its most incomprehensible.....

1 lb = 16 oz = 256 drams = 7000 grains

1 oz = 16 drams = 437.5 grains

1 dram = 27.34375 grains

So the gooseberry weighed 902.34375 grains plus 21 grains - a total of 923.34375 grains.

How can anyone seriously suggest that a system that requires a conversion factor of 27.34375 between two inter-related units is superior?

Incidentally, British Airways guide to this event tells us that "Eighteen drams is approximately 1oz"

http://events.britishairways.com/sisp/?fx=event&event_id=35651

It's not just Tony that is unsure of the definitions of imperial measures!

In the US, it is common to switch to metric after you go less than about half an ounce or so, since the dram and other smaller units are unknown. The only exception I can think of is the grain, used for measuring gold and such. A similar phenomenon is seen with length, when Americans will sometimes switch to millimetres for small lengths - 0.5 mm lead, for example.

"The only exception I can think of is the grain, used for measuring gold and such"

There are two meanings to the grain. The second definition was used by jewelers but is now obsolete. It was equal to exactly 50 mg, thus was more metric then imperial. Go to any jeweler today and you will see gram scales. Gold is sold in grams by jewelers and weighed on gram scales. Even if New York prices it in ounces, that figure is converted to grams for real world usage.

From Rowlett:

grain (gr) [1]

a traditional unit of weight. The grain, equal to 1/480 troy ounce (see also pound [2]), or exactly 64.798 91 milligrams, was the legal foundation of traditional English weight systems, with various pounds being defined as a specified number of grains: 5760 grains in a troy pound and 7000 grains in an avoirdupois pound, for example. In the version of the troy system used by jewelers, there are 24 grains in a pennyweight and 20 pennyweight in an ounce. In the version used by apothecaries, there are 20 grains in a scruple, 3 scruples in a dram, and 8 drams in an ounce. Originally the grain was defined in England as the weight of a barleycorn. This made the English grain larger the corresponding grain units of France and other nations of the Continent, because those units were based on the weight of the smaller wheat grain.

grain (gr) [2]

a unit of weight formerly used by jewelers in measuring diamonds and other precious stones. The jeweler's grain is exactly 1/4 carat. Now that the carat has been standardized at 200 milligrams, the jeweler's grain is exactly 50 milligrams, or approximately 0.7716 troy grain. This unit is widely used for measuring pearls, so it is sometimes called the pearl grain.

"REPLY: There are 16 drams to an ounce which is fine. And of course there are 7,000 grains to an ounce."

The grain is only 65 mg, thus the grain is not fine enough for medical or any scientific work where milligram or smaller precision is necessary. Drug dosage is universally measured in milligrams or millilitres per kilogram of body mass. You can't get precise enough with grains.

Grains may have served a purpose when most of your medical personnel were nothing more then witch doctors, but in the age of microbiology high precision units that only SI can provide are required.

Beranger, re "How can anyone seriously suggest that a system that requires a conversion factor of 27.34375 between two inter-related units is superior?"

REPLY: Why don't you 'phone the Chairman or Secretary of the Egton Bridge Old Gooseberry Society? They're perfectly happy with drams and grains. Why, people have been weighing gooseberries like that for centuries

Tony Bennett wrote

<<
On page 7 of the now-legendary Customary Measures Society's "Weights and Measures: Britiain's Way Ahead" is a full colour picture of an article from the Whitby Gazette in 2003 titled: "Champion gooseberry sets record".
>>

I did a search on the Internet for this legendary publication - I got two hits - both on the BWMA site! In such circumstance, I don't think that the word "legendary" is appropriate.

I've never seen a scale with a precision of less than an ounce before.

Thanks to Danny for reminding us that gold is measured in troy ounces. For once you've been useful!

<<
I've never seen a scale with a precision of less than an ounce before.
>>

Go to the Post Office and you will see one on the counter which weights down to 1 gm.

"Go to the Post Office and you will see one on the counter which weights down to 1 g."

Martin,

Also go to a jeweler and you will fined precision gram scales used to weigh gold and other items sold only by the gram.

Scientists, hospitals, chemical labs, etc. have precision balances that measure into the micrograms, some into the nanogram range.

With imperial there are limits to precision, but with SI precision is limitless.

I was talking about scales with oz on them - I've never seen one that goes under an ounce.

BTW - What use does 1 gramme have on a post-office scale - the lowest price stamp available does not change on a tolerance of a gramme.

Working around Bucks way this week did a quick check after my last visit to Amersham market on Sycamore Rd. Nice to see the street stalls now got the metric price all boldly above the imperial.
Now they are in line with the Budgens, Iceland and Fruit Shop outside of which they were all operating and priced per kg only.
Called up about another "cheaper by the lb" con artist in a central London borough yesterday and was surprised that the TSO matters are all now dealt with centrally. Makes the chasing up of these lot much easier :)
The great thing about seeing the lb con dealt with ( and the nice new scales) is the comfort of knowing when your "ammended signs" have been all changed to metric, the kilo will remain!
"Teedle Pop Ald Chips and Jelly Hickey Stucks to you all."

re (POUND HOUND): "Working around Bucks way this week did a quick check after my last visit to Amersham market on Sycamore Rd..."

REPLY: Pound Hound will have to get out more. I've been to the folowing places in the last few months - and *all* of them have butchers, fishmongers, greengrocers etc. boldly dispalying offers in lbs.: Windermere, Ambleside, Barrow-in-Furness, Broughton-in-Furness, Shrewsbury, Church Stretton, Selby, Bishop's Castle, Ilkeston, Southwell - and many others.

P.S. Is 'Pound Hound' the 'dog' from the three men, one woman and a dog?

Thanks pound-hound for showing us being legal works both ways. Keep up the good work.

<<
With imperial there are limits to precision, but with SI precision is limitless.
>>

I don't know if it's worth asking, but Daniel, could you explain this?

Steve Wrote

<<
I was talking about scales with oz on them - I've never seen one that goes under an ounce.
>>

Well you could go into any kitchenware shop. There are a number of electronic scales available these days. If you visit http://www.argos.co.uk/webapp/wcs/stores/servlet/Search?storeId=10001&catalogId=3801&langId=-1&searchTerms=kitchen+scales&go.x=13&go.y=13

you can admire that Argos range.

Johns-MI:
"The Guiness Book of Records is full of obscure people doing obscure things most of us wouldn't think to do. Much less competition for setting a record that way. I certainly plan to leave their record unchallenged. :)"

Stan:
Too true. I seldom watch it. Frankly I find some of the things people do on that lunatic programme disgusting. I can't stomach it.

However I did notice one odd thing when they were dealing with a more sober issue. Namely the world's tallest man. They measured it in metric but had to calculate the imperial equivalent for the plebs.

Martin/Steve
Post office digital scales usually indicate to the nearest 2g. I'm shocked that Steve cannot recall imperial shop scales indicating to the nearest 1/8 oz though! Must be a good few years since he saw one :-) :-) :-)

Steve (re post office scales)
Think about it - as the weight goes up, the price doesn't go up in exact proportion.
56g = 21p
58g = 21p
60g = 21p
62g = 35p
64g = 35p

The scales have to be a bit more accurate to take account of the odd pricing structure.

Bud
I don't think that Daniel meant this, but he is technically correct. Only one weight in the world is truly accurate, all the other (metric & imperial) weights that derive from it will have slight errors. We are stuck with this situation until scientists agree on a better method of defining weight than "that lump of metal over there weighs 1kg (by definition)"

Tony
"Why, people have been weighing gooseberries like that for centuries"

I am honestly surprised by this. I'll quite happily admit that I have previously seen both drams & grains in use but usually as individual units - I would have expected the weight of the gossies to have been given in grains alone or in troy.

Do you happen to know whether the weighing machine used actually indicates in the bizarre combination of units used - or is it just a standard chemist's balance with 2 sets of weights in use?

I see that there are only around 7 other competitions still in existence - and that they seem to use pennyweights & grains (1 pennyweight = 24 grains, 20 pennyweights = 1 ounce apothecaries, 12 oz.ap. = 1 lb troy)

At least that system seems to have some slight relationship between the units (unless you are claming to be proficient in the 27.34375 times table!)

Daniel
A full set of Imperial Local Standard weights would contain a set of grain weights. The smallest would weigh 0.01 grains. This is slightly smaller than the smallest Metric Local Standard (1mg), but both are adjusted to the same tolerance (0.06mg). It is possible to subdivide imperial units further (usually decimally though)

"Bud
I don't think that Daniel meant this, but he is technically correct. Only one weight in the world is truly accurate, all the other (metric & imperial) weights that derive from it will have slight errors. We are stuck with this situation until scientists agree on a better method of defining weight than "that lump of metal over there weighs 1kg (by definition)""


Measurements Improve Prospects for International Redefinition of the Kilogram


A leading experimental method for defining the kilogram in terms of properties of nature is now more accurate than ever, scientists at the Commerce Department's National Institute of Standards and Technology (NIST) report. The advance may move the scientific community closer to redefining the kilogram, the only one of the seven basic units of the international measurement system still defined by a physical artifact.

The latest NIST work, described in the October 2005 issue of Metrologia, confirms the institute's 1998 results using the same method while reducing the measurement uncertainty by about 40 percent, thanks mainly to improvements in the hardware used in the experiments.

"The fact that we got the same values gives us confidence that the uncertainties we're quoting are probably reasonable," says NIST physicist Richard Steiner, lead author of the paper.

Scientists at NIST and other institutions around the world have spent years conducting experiments to find a reliable definition based in nature to replace the current international standard for the kilogram, a century-old cylinder of platinum-iridium alloy about the size of a plum. The new results mean that the NIST method, using an apparatus called the watt balance or electronic kilogram, is almost accurate enough now to meet the criteria for redefinition.

Any decision about when and how to redefine the kilogram would be made by an international group, the International Committee for Weights and Measures, CIPM, and ratified by a General Conference on Weights and Measures (CGPM), which next meets in 2007. The CGPM likely will delay a redefinition until other groups confirm the new NIST results.

The primary kilogram standard is currently maintained at the Bureau International des Poids et Mesures (BIPM) near Paris. Although the cylinder is housed in a special vault under controlled conditions, its mass can drift slightly over time and can change because of contamination, material loss from surface cleaning or other effects. Moreover, the standard is accessible only at BIPM and could be damaged or destroyed. By contrast, a property of nature is by definition always the same and can, in theory, be measured anywhere.

The other six basic units of the international measurement system are the meter (unit of length), second (time), ampere (electric current), Kelvin (temperature), mole (amount of substance) and candela (luminous intensity). All six are defined in terms of properties of nature and can be measured at any suitably equipped laboratory.

The NIST watt balance is a two-story-high apparatus designed to redefine mass in terms of fundamental physics and quantum standards. It measures the force required to balance a 1-kilogram mass artifact against the pull of Earth's gravity, as well as two electrical values (see graphic). These measurements are used to determine the relationship between mechanical and electrical power, which can be combined with several equations to define the kilogram in terms of basic properties of nature.

One of these properties is the Planck constant, the ratio of the energy of radiation to its frequency. This is one of an extensive set of "fundamental constants" used by scientists to predict a wide range of phenomena. The latest NIST value for the Planck constant reported in the new paper (6.62606901 x 10 -34 Joule seconds) is equivalent to the 1998 NIST result and a 1988 measurement by the National Physical Laboratory in the United Kingdom, which are the two other most accurate values.

The watt balance is one of two leading approaches for redefining the kilogram. The other approach involves counting how many atoms of a specific atomic mass equal the mass of 1 kilogram. The latest NIST measurements, which have an uncertainty of 0.052 parts per million compared to 0.087 parts per million in the 1998 experiments, are far more precise than any previous results by any research group using either approach, according to Steiner. The total uncertainty is calculated by adding up more than 20 sources of error.

The precision of the latest NIST measurements is roughly equivalent to the suspected drift in the current kilogram standard's mass over time, Steiner says. The NIST researchers hope to further reduce the uncertainty of the watt balance measurements to 0.02 parts per million within the next year or so, to reach the level of precision needed for commercial mass measurements in the near future.

The measurements reported in Metrologia are the product of numerous improvements in NIST's watt balance, including reconstruction of most of the hardware to eliminate many sources of error. The coil and balance were enclosed in a fiberglass vacuum chamber, which reduced the need for air corrections. In addition, the coil was stiffened to reduce flexing that caused excess "noise" in the signals being measured. Noise was reduced to one-fifth of the level of the 1998 experiments. Researchers also improved the alignment of instruments, temperature control and the software used for management and analysis of the experiments.

http://www.nist.gov/

Posted 19th September 2005

Beranger:
"I don't think that Daniel meant this, but he is technically correct. Only one weight in the world is truly accurate, all the other (metric & imperial) weights that derive from it will have slight errors. We are stuck with this situation until scientists agree on a better method of defining weight than "that lump of metal over there weighs 1kg (by definition)"

Stan:
All the kilogram mass prototypes are equal to one another within the limits of measurement accuracy. The idea that the Paris prototype is more accurate than the others is false. If they were able to detect a difference between a secondary prototype and the main referee then it would be corrected.

"Daniel
A full set of Imperial Local Standard weights would contain a set of grain weights. The smallest would weigh 0.01 grains. This is slightly smaller than the smallest Metric Local Standard (1mg), but both are adjusted to the same tolerance (0.06mg). It is possible to subdivide imperial units further (usually decimally though)"

Can you provide a website to show this?

Daniel

The legislation that sets out UK local standards is the Weights & Measures (Local and Working Standard Weights & Testing Equipment) Regulations 1986.

It is too old to be on the Stationery Office site (which only goes back to 1987) & has been amended since.

However, the 1936 Irish national standards are set out at http://www.acts.ie/print/zza8y1936.1.html

Look at Part III of the schedule, Decimal Grain Weights.

" 2. Twelve standards of 5, 3, 2, 1, 0.5, 0.3, 0.2, 0.1, 0.05, 0.03, 0.02, and 0.01 grains respectively, all enclosed in a wooden box marked with the figures "3211"."

Does that prove that 0.01 grain weights exist?

You'll just have to take my word as to the tolerances on UK local standards - or you could buy a hard copy of the 1986 regulations (only £6 from HMSO)

To find decimal parts of your smallest imperial weight, you would follow exactly the same procedure that you would for your smallest metric weight.

Work out the discrimination threshold, weight value per division & 95% confidence interval of the repeatability of your balance & go from there.

Stan

http://www.bipm.org/en/scientific/mass/verifications.html

http://www.bipm.org/utils/common/pdf/3eVerificationkg-EN.pdf

Check the graphs & tables. I believe BIPM give a certificate stating the error rather than try to adjust the weight.

Stan: "However I did notice one odd thing when they were dealing with a more sober issue. Namely the world's tallest man. They measured it in metric but had to calculate the imperial equivalent for the plebs."

Nice to see we were watching the same show, Stan - despite you saying you don't watch it.
Note how they did the metric measures in the source country (Libya?) and in the UK studio they made him stand against an imperial only measuring device?



By the way - To Berenger - The cryptic "King" message? I believe him to be the Pound Hound (who should surely call himself the Kilo-hound?).

Living near Amersham I also know that he's a complete liar.

Yer picked the wrong town this time, matey! Take care to pick one that none of us frequents in future!!!!

LOL!
ROTFL!!

Stan: "However I did notice one odd thing when they were dealing with a more sober issue. Namely the world's tallest man. They measured it in metric but had to calculate the imperial equivalent for the plebs."

Nice to see we were watching the same show, Stan - despite you saying you don't watch it.
Note how they did the metric measures in the source country (Libya?) and in the UK studio they made him stand against an imperial only measuring device?



By the way - To Berenger - The cryptic "King" message? I believe him to be the Pound Hound (who should surely call himself the Kilo-hound?).

Living near Amersham I also know that he's a complete liar.

Yer picked the wrong town this time, matey! Take care to pick one that none of us frequents in future!!!!

LOL!
ROTFL!!

Stan: "However I did notice one odd thing when they were dealing with a more sober issue. Namely the world's tallest man. They measured it in metric but had to calculate the imperial equivalent for the plebs."

Nice to see we were watching the same show, Stan - despite you saying you don't watch it.
Note how they did the metric measures in the source country (Libya?) and in the UK studio they made him stand against an imperial only measuring device?



By the way - To Berenger - The cryptic "King" message? I believe him to be the Pound Hound (who should surely call himself the Kilo-hound?).

Living near Amersham I also know that he's a complete liar.

Yer picked the wrong town this time, matey! Take care to pick one that none of us frequents in future!!!!

LOL!
ROTFL!!

Nice to see network54 is still a stable piece of software (!)

If this was 'Just a Minute', I would press the buzzer and say 'repetition'

I'm just surprised noone blamed the EC for making Steve respond in triplicate

Actually it was tha tabloids.

3 responses?

No?

Think.....

There's 3 feet in a yard.

The papers all talk in "yards" (,miles,inches, etc).

So it MUST be the tabloids.

Thats what makes the UK imperial, that is.

<<
I don't think that Daniel meant this, but he is technically correct. Only one weight in the world is truly accurate, all the other (metric & imperial) weights that derive from it will have slight errors. We are stuck with this situation until scientists agree on a better method of defining weight than "that lump of metal over there weighs 1kg (by definition)"
>>

The pound and the kilogram are related to each other by way of a constant conversion factor that, by definition, has zero uncertainty. When you multiply a number by a constant with zero uncertainty, you do not introduce any additional uncertainty. The uncertainty in the product is the same as the uncertainty in the original value. Therefore, the uncertainty is the same whether you are measuring in pounds or kilos.

Bud

"The pound and the kilogram are related to each other by way of a constant conversion factor that, by definition, has zero uncertainty."

Nearly. Try

"The definition of the pound and the definition of the kilogram are related to each other by way of a constant conversion factor that, by definition, has zero uncertainty."

The international prototype kilogram weighs exactly 1kg by definition. Any attempt to reproduce it exactly will have some tiny degree of measurement uncertainty. Any attempt to reproduce any fraction or multiple of it will have some tiny degree of measurement uncertainty.

"Therefore, the uncertainty is the same whether you are measuring in pounds or kilos"

Agreed, with respect to every weight in the world except the international prototype kilogram. The uncertainty will increase as you drop down the various classes of weights.

Bud wrote
<<
"that lump of metal over there weighs 1kg (by definition)"
>>

shouldn't that be "... has a mas of ...".

Since air has a density of the order of 1kg/m^3 and the protoype kilogramme a density of the order of 20tonnes/m^3, then, if weighed in air, the prototype would have an apparent loss of weigh of the order of 0.005% as described by Archimedes principal. This apparent loss of weight is significant if the accuaracey of the measurement is 1 part in 10^8.

<<
Agreed, with respect to every weight in the world except the international prototype kilogram. The uncertainty will increase as you drop down the various classes of weights.
>>
That's true, but my point was that the units do not affect the uncertainty. If you are comparing your mass to one of the lower-level standards, there will be some uncertainty, but it will be the same whether you express your result in pounds or kilos.




Martin, I don't think I said the line that you quoted above. But at any rate, I don't know of any way of measuring the mass of an object without weighing it. I would assume that they weigh the prototypes in a close-to-perfect vacuum under conditions such that they know the value of g. If you know of another method, I would be interested in learning more.

Sorry Bud, I copied the note form your post, but I failed to notice that you were quoting Daniel.

BTW, if you visit the BIPM site you might well see descriptions of altenative methods of measuring mass.

The pound and the kilogram are related to each other by way of a constant conversion factor that, by definition, has zero uncertainty. When you multiply a number by a constant with zero uncertainty, you do not introduce any additional uncertainty. The uncertainty in the product is the same as the uncertainty in the original value. Therefore, the uncertainty is the same whether you are measuring in pounds or kilos.


By definition, one avoirdupois pound is equal to exactly 453.592 37 grams. With five digits to the right of the decimal place the uncertainty increases if that level of accuracy can not be met. In practical applications, where conversion factors of 453.6 or 454 g is often used, then the uncertainty is increased greatly.

And how does this effect the ordinary person going about his daily tasks?

<<By definition, one avoirdupois pound is equal to exactly 453.592 37 grams. With five digits to the right of the decimal place the uncertainty increases if that level of accuracy can not be met. In practical applications, where conversion factors of 453.6 or 454 g is often used, then the uncertainty is increased greatly. >>

But did they really use a rounded conversion factor, or did they use exact conversion and then round to an appropriate number of decimals, based on the accuracy inherent in the initial number.

Legal requirements for trade weights vary from place to place, but tend to be around plus/minus 0.5%. 1 lb ± 0.5% is 451.32441 to 455.86033 g. Stating it as a rounded value of 454 or 453.6 g has not increased it's uncertainty at all.

Certainly conversions can be screwed up if the accuracy of the initial number is not properly understood. In general any such number (on food packages) will be a nominal with a min/max tolerance. The minimum/nominal/maximum should all be converted exactly, then appropriate rounding applied. Under FPLA, the larger claim (using exact conversion) is the one tested for accuracy, and the supplemental claim is usually rounded down to avoid legal difficulties. So if 454 g is claimed, it has to be just over a pound; quite often only 453 g is claimed if the design weight is 1 lb.

"So if 454 g is claimed, it has to be just over a pound; quite often only 453 g is claimed if the design weight is 1 lb."

They don't fill that close. Check the weight of something that is marked as 454 g. You will probally find it having a mass of 460~470 g. This way they are covered if any question of cheating arises.

I'll put my hands up. I was the first to post

<<We are stuck with this situation until scientists agree on a better method of defining weight than "that lump of metal over there weighs 1kg (by definition)">>

Martin is correct - I should have said "has a mass of"

Bud
"That's true, but my point was that the units do not affect the uncertainty."

Agreed. Any weight manufacturer could make a 500g or 1lb weight with equal precision.

Daniel
"By definition, one avoirdupois pound is equal to exactly 453.592 37 grams. With five digits to the right of the decimal place the uncertainty increases if that level of accuracy can not be met."

Yes - and the same argument would apply to a weight of 1000.00000 grammes.

John
"Under FPLA, the larger claim (using exact conversion) is the one tested for accuracy"

In the UK, it is now done differently. The metric indication is the one tested for accuracy. 453g/1lb appears less often than 454g/1lb

Daniel
"They don't fill that close. Check the weight of something that is marked as 454 g. You will probally find it having a mass of 460~470 g. This way they are covered if any question of cheating arises."

Are you weighing gross or net Danny? Usually you will find that the bigger the company, the closer the average package is to the nominal quantity. On bulk items like bread, a factory manager would be asked some very hard questions by head office if the 800g loaves were going out at an average of 815-820g. A small one-man baker (50 loaves per day or so) would be delighted with that average

Shouldn't respond to front page first - above was me!

<<
By definition, one avoirdupois pound is equal to exactly 453.592 37 grams. With five digits to the right of the decimal place the uncertainty increases if that level of accuracy can not be met.
>>
No it doesn't. Go look up the rules of significant figures.

If the person testing your local pound weight checks it to only 2 or 3 of the digits, then the accuracy is compromised.

Yes, imagine how hungry you'd be missing out on that important miniscule crumb of cheddar cheese?

I'd be starving.

Now think about the effects on those mice in the Tom and Jerry cartoons. Especially that grey one with the French accent. He needs to build up a bit.

Yes, imagine how hungry you'd be missing out on that important miniscule crumb of cheddar cheese?

Plain old Cheddar? I prefer Bishop Stinking.

<<
Yes, imagine how hungry you'd be missing out on that important miniscule crumb of cheddar cheese?
>>

Extreme accuracy is seldom needed in the kitchen. However I have written computer programs in which the following measurements are taken -

1) The mass of a piece of oil-bearing rock (The fluid in the spaces between the grains of sand making up the rock contains a mixture of water and oil)

2) The mass of the same piece of rock once once all of the liquid has been driven out

3) The mass of the same piece of rock after mercury has been forced into the rock under pressure. A number of measurements are taken at different pressures.

The required accuracy for such measurements are typically 1 part in 5,000 or better. If you visit http://www.iccsltd.com/SiHgma.html you can see some of the graphs that have been generated from this process.

But my point is that if you have a measurement with a given accuracy, the accuracy will remain the same if you change it to different units. For example, 1 lb with an accuracy of +/- 1% is equal to 450 g, not 453.6....