Weight "standard" from household items?

[ivan747]

Today I dug out an old mechanical kitchen scale I am going to use to weight home built RC planes and general electronics.

I think it is a bit out and it's reading less weight than it should, so I need a way to confirm that.

Does anybody know a household item that has a more or less standard weight? I have thought of using coins with little circulation, AA batteries (since there are data sheets with nominal weight online) and a known volume of water. What would be the best solution? I am guessing water because I would only have to get a half-decent way of measuring volume and I have that.

Obviously buying a set of calibrated weights (I don't know the name of those) wouldn't be any good. I could just buy a new digital scale instead.

I would be happy with 5% accuracy, about 2.5% would be great, 7% would be borderline. I think the scale could be anywhere from 15% to 5% out right now.

Of course, there's no way of adjusting the scale, but I don't mind that.




Edit: removed the annoying Tapatalk signature.

[xrunner]

I have thought of using coins with little circulation, ...

Yea you could use coins, they have specific weights -

http://www.usmint.gov/about_the_mint/?action=coin_specifications

[TheBay]

Would foodstuffs be accurate? Do packages actually go by their weight or is there discrepancy, such as meat from the butcher in the supermarket, not going to be a nice way to measure but their scales have to be accurate so ask for a certain weight of meat and use that? Silly idea I know

[johnh]

 Coins

Used to weigh all the coins for a social club as I was bagging them, with a electronic kitchen scales accurate to 1 gram.

Bank used to reweigh every thing, never had a problem. 

[GeoffS]

I'd go with water as long as you have an accurate volume measurement.

[Rerouter]

I would also say the volume of water, just note and account for the weight of the jug,

[TheBay]

Surely you would need an accurate weight of the jug first?

[Rerouter]

not at all, as its a differential check of the span accuracy, zeroing is pretty obvious when you have nothing on the device

[ivan747]

Well, I got off the chair and did some measurements. I planned on filling a container with 1L of water. That has a mass of 1kg plus the weight of the container. But before that I placed the container in the scale and nulled out the reading. Then I filled it as precisely as possible with 1L of water.

The scale measured 900 ridiculous grams. Amazing. It's 10% out. That's not even OK for kitchen applications I think. "Well maybe if it's linear it doesn't matter that much".

So I went and emptied the container, checked if the scale was still null. It was, so I filled it with 2L. It should give me 2kg, which is the full scale of this kitchen scale. When I measured it gave me something close to 1850g. I *could* live with that but since this is mechanical, inaccurate and already belongs to the kitchen, I think I'm gonna get a small digital scale for the lab.

Cheers! We did science tonight, hehehe >

[TheBay]

Shame it's not linear across the range, that way you could just change the marks on it or just use a table

You could still make a table, but it is not worth the hassle!

Well, I got off the chair and did some measurements. I planned on filling a container with 1L of water. That has a mass of 1kg plus the weight of the container. But before that I placed the container in the scale and nulled out the reading. Then I filled it as precisely as possible with 1L of water.

The scale measured 900 ridiculous grams. Amazing. It's 10% out. That's not even OK for kitchen applications I think. "Well maybe if it's linear it doesn't matter that much".

So I went and emptied the container, checked if the scale was still null. It was, so I filled it with 2L. It should give me 2kg, which is the full scale of this kitchen scale. When I measured it gave me something close to 1850g. I *could* live with that but since this is mechanical, inaccurate and already belongs to the kitchen, I think I'm gonna get a small digital scale for the lab.

Cheers! We did science tonight, hehehe >

[Rick Law]

Water works very well.  I did exactly that with my bathroom scale.  Another method is to use your local shipper.

I see you are not in the USA, but I suppose it should be similar where you are.  Pack a box of approximate (gut feel) 1kg.  Go to your nearest place that do shipping - post office, UPS, FedEx, DHL, etc., most of them have fairly accurate scales available to customers, or if you cannot directly access it, many of them will weight it for you.  That can serve as your reference weight.

[ivan747]

Sure I could go there, they have pretty accurate scales, but I think water wins for being convenient.

[Lightages]

As far as food packages being exactly the right weight, don't count on it. Most companies don't want to waste product so they try to keep the weights as close to exact as possible but at the same time they don't want to get caught with shorting the customer. Because of this the packages tend to weigh a little but more than their label.

[IanB]

I have an inexpensive electronic kitchen scale that judging from a few basic tests appears to be accurate to the nearest gram, which is pretty good for a consumer device. So I would suggest that you just forget the spring scale and buy any reasonably priced electronic scale.

The other option of course would be a mechanical balance scale, but they are not as convenient to use (and they are at least as heavy as the collection of weights they use for balancing).

[Rufus]

As far as food packages being exactly the right weight, don't count on it. Most companies don't want to waste product so they try to keep the weights as close to exact as possible but at the same time they don't want to get caught with shorting the customer. Because of this the packages tend to weigh a little but more than their label.

Depends on regulation where you are. In some places manufacturers are allow to control the average weight/volume of packages so average weight/volume of packages depends on the measurement accuracy not the accuracy of the filling/packaging equipment. In such places you are only slightly more likely to get an over rather than under weight package.

[SeanB]

Most liquids are packed volumetrically, so you will get a volume that is within 1% of the set point. The problem is some products ( like perfumes and such sold in clear glass) are often sight line filled, so that all containers are filled to the same line on the glass, irrespective of the actual inside volume of the bottle. This can vary by about 5% for common glass blown bottles. There will not often be any indication of the fill volume method on the bottle.

Good for the use of density to check, very neat solution and reasonably accurate and repeatable.

[urbis]

A bag of sugar or your mobile phone is always a good option as you can easily find the weight online.

[Mr Smiley]

Have you thought of

1 bag of sugar,,,, the container is paper

1kg or 500g of pasta,,,,, the container is clear thin plastic

Perhaps the plastic and the paper weight can be classed as insignificant relative to the weight of their contents  It will be down to what resolution you want to measure to.

The displayed weight should not include the weight of the container. Unless you buy loose fruit/veg. In that case find the thinnest and smallest bag they supply for that purpose, all those added milligrams add up to a tidy prophet.   

 

[Rufus]

Have you thought of

1 bag of sugar,,,, the container is paper

1kg or 500g of pasta,,,,, the container is clear thin plastic

In Europe the weight on your bag of sugar or pasta will be followed by an 'e' mark which tells you a 1000g bag of sugar won't be more than 3% light and could be any % heavy.

http://en.wikipedia.org/wiki/Estimated_sign

[amyk]

A bag of water (1L of it) can also work, if you really want the container weight to be insignificant. It's also surprisingly heavy for such a small object.

[JackOfVA]

Supermarkets here in the USA have installed very accurate digital electronic scales in the produce departments - the customer puts a potato or whatever on the scale and weighs it, enters the produce code and presses a button and out comes a printed label with bar code with the price, weight and item description.

You could take a collection of items to your local supermarket produce department assuming it has a similar arrangement and weigh them. 

The scales are required by law to be calibrated every year and to have an inspection sticker certifying they have been verified by the local government weights and measures department to be within tolerance.

[Maxlor]

What makes you so sure your containers measure volume more accurately than your scale measures weight?

[SeanB]

Generally supermarket massmeters are accurate, and many count in 1g increments. Best is to go into the supermarket and take a bag of sugar and place on the massmeter and remember the mass of that bag, then place it in a separate lastic bag so that you keep any loose sugar with it.

[ivan747]

What makes you so sure your containers measure volume more accurately than your scale measures weight?

Nothing, to be honest. I could use different containers to confirm it or go to the supermarket. I don't trust my government's calibration stickers. I've seen many many scales with calibration due.   

[Rick Law]

Generally supermarket massmeters are accurate, and many count in 1g increments. Best is to go into the supermarket and take a bag of sugar and place on the massmeter and remember the mass of that bag, then place it in a separate lastic bag so that you keep any loose sugar with it.

Try something more durable.  Grab a few CANS or GLASS jars of cheap products with around the weight you want.  Weight them (write it down!) then buy them..

The post office mail/scales (in the US) are great.  The one I have is accurate down to 1/10 oz to about 5 pounds (I think, 3 pounds for sure).  Good enough to use to measure the weight of a 1gallon empty plastic jug and measure the amount of water actually added into it.