25 replies to this topic

[lord_dranack]

  But to be precise you also need to be accurate.

Not necessarily.
For example you could have a set of scales that when weighing a 100g weight, give the mass to be 105g every time. These scales are not accurate, as they give the wrong mass, but are precise, as they give the same reading every time, so they can be precise without accuracy.

However to be accurate, precision is helpful, for otherwise you would not know when the correct value was shown. With a hundred gram weight if it war recorded as 95g, 100g, 102g,105g, etc. this is not much help as you do not know which is the accurate answer!

Weighing on a precice set of inaccurate scales is, as Steve said, all most pyros realy need
Absolute accuracy is not crucial, only accuracy relative to the other things you are weighing (at least in terms of most pyrotechnics)

[adamw]

Yes. I think I meant it the other way around. A kind of a paradox.

[Old1953]

Yes. I think I meant it the other way around. A kind of a paradox.

Virtually every district or area in the world has someone local in charge of weights and measures. You can take your scales to them for calibration, but ask about the fees first - some places high, some low, some may be free.

Downside to this is they may think you are dealing drugs.

In the UK I believe this is the office you contact.

http://www.tameside....andmeasures.htm

[broadsword]

Itreally does not matter!
If you scales are out, why does it matter. All that you measure will be out so it works out at the same ratios!

[ProfHawking]

Itreally does not matter!
If you scales are out, why does it matter. All that you measure will be out so it works out at the same ratios!

Yeah this has been mentioned. But the proplem occours when the scales are not calibrated right. So say it measures 100g correctly, but if you put 200g weight on it it might say 250g. Therefore if you stick 400g on it, it will read 500g
You have to check it with at two (or more if you want to be sure) same value weights.

Easiest way to do it, is get two things the same weight, like two ?2 coins for small scales, or same glasses full of water or something for larger scales.
Weigh one, then put both on. if the reading is not exactly twice of the first reading then youve got a problem.

Edited by ProfHawking, 18 February 2005 - 11:11 PM.

[blueflame]

Would this change the weight a lot??
if it was a dent, it would be the same weight but in a different shape???

i once worked in the gold trade and at the end of every day we would use a vacume cleaner to clean the floor, the dust bag would be put aside and the gold dust would be removed at a later date, it probably worked out to a few pence per night in dust but never the less it was still gold dust from a gold item that was scratched. the company would weigh this dust at some point to ensure the total weight of gold was as close as poss to the time it was 1st weighed. so clearly scratches do make a difference.

my 1st post was actually refering to general chips and denting of the coin over time but seeing as though you made a point about my off the cuff remark on "dents" then i would suggest there clearly is a loss however small during a dent ,and i would also suggest that this small weight loss of the coin or what ever it is that got dented would be located on the offending object that caused the dent on the point where impact took place.

Edited by blueflame, 08 March 2005 - 10:50 PM.

[mnementh]

Hi guys,
sorry to be pedantic here but a scratch and a dent are two entirely different things.

A scratch infers that material is removed and therefore, the weight decreases (albeit by a very small amount), while a dent simply deforms the measured object unit and does NOT alter the weight.

Dents are irrelevent, the weight remains the same, whereas scratches will, to a very minor degree, alter the measured weight.

HTH,
Sandy

[blueflame]

Hi guys,
sorry to be pedantic here but a scratch and a dent are two entirely different things.

A scratch infers that  material is removed and therefore, the weight decreases (albeit by a very small amount), while a dent simply deforms the measured object unit and does NOT alter the weight.

Dents are irrelevent, the weight remains the same, whereas scratches will, to a very minor degree, alter the measured weight.

HTH,
Sandy

ok i will be even more pedantic . for this debate we will stick to the pound coin situation, are you saying that a pound coin (object 1) if dented by another object which we can call object 2, that no material from object one would remain on object 2 after imapct?
i am quite sure that some of the matter from object 1 will be on object 2 even if it is at forensic level. but this minute weight should not play any part in pyro but never the less it is still matter that has weight.

[Andrew]

I'm going to be even more pedantic. What about when you pick up the weights, a few thousand atoms will end up on your hands or the implement you picked them up with? Or what about corrosion, or your latitude, or your local "g" variations, or the way your scales are facing, or where the moon or Jupiter is? Come on! we have to draw the line some where. In pyro, I bet almost everyone goes "that'll do" or sprinkles a little more on, and I bet that not one of them will notice the difference. Scratches are perhaps on the Light or Ridiculous side, but not quite Ludicrous though, worth a little thought.

I wonder if anyone spots the pun and movie connection.

Edited by Andrew, 30 March 2005 - 02:29 PM.

[blueflame]

I'm going to be even more pedantic. What about when you pick up the weights, a few thousand atoms will end up on your hands or the implement you picked them up with? Or what about corrosion, or your latitude, or your local "g" variations, or the way your scales are facing, or where the moon or Jupiter is? Come on! we have to draw the line some where. In pyro, I bet almost everyone goes "that'll do" or sprinkles a little more on, and I bet that not one of them will notice the difference. Scratches are perhaps on the Light or Ridiculous side, but not quite Ludicrous though, worth a little thought.

I wonder if anyone spots the pun and movie connection.

arrrgh enough already ! i read your reply 3 times but still cant see the pun/movie connection .to change to subject a touch i always fancied getting myself some little old antique highly polished brass scales in a little glass display box, i think the wacky backy brigade use replicas of the type i like.

[Andrew]

arrrgh enough already ! i read your reply 3 times but still cant see the pun/movie connection .to change to subject a touch i always fancied getting myself some little old antique highly polished brass scales in a little glass display box, i think the wacky backy brigade use replicas of the type i like.

pun is the use of the word "Light", and that, "Ridiculous" and "Ludicrous", are from Space Balls. I think it is a great movie. I have a few real chain drive balances, they are great. The best ones have a resolution of 5mg, but being analog you can easily do better than that, and a full scale of 400g. Lots of brass and ivory, draft excluders and bakolite dishes, well there not that old. I'll post some pictures when I can. I've seen the wacky backy brigade scales and they are sh*t!!! in my opinion only good for decoration. They do look shiny though.