31 replies to this topic

[Draco_Americanus]

I have a calibration weight that did come with the cheap digital scale.
After a bit of thinking I belive the main problem I am having with the cheap scale is it's out of calibration, so to Sizzle I belive thats my main problem with it.
So far I love the Ohaus, JE500

[sizzle]

Well, on measuring a ?2 coin it displays 14.2g, so if fishy1's information is right then they are pretty much accurate.

[fishy1]

Well, on measuring a ?2 coin it displays 14.2g, so if fishy1's information is right then they are pretty much accurate.

yep, 14.2g is about 1.5% off, nothing bad at all.
you could try it with two ?2 coins, and so if you get about 28g you know they're consistent. if however, you get 35g or something like that, it's not good.

[BlackSky]

I may return to the beginning of the post. I'd like to add some clearification for those who are new in the field.

For example, When you see this formula

10:15:75/S:C:KNO3

This means that the parts are as following:
10% is for S (Sulfer or Sulpher)
15% is for C (Carbon or Charcoal)
75% is for KNO3 (Potassium Nitrate)
_____________________________________
Another thing, What about the + Sing ?
If you see for example this formula :

10:15:75/S:C:KNO3 +10%Dx

Then you have the following:
10% Sulfer
15% Coal
75% KNO3
And in addition of 10% of Dextrin
Thus, You will get a total of 110 not 100.

Hope this helps.

Edited by BlackSky, 21 February 2006 - 03:54 PM.

[karlfoxman]

I may return to the beginning of the post. I'd like to add some clearification for those who are new in the field.

For example, When you see this formula
10:15:75/S:C:KNO3
This means that the parts are as following:
10% is for C (Carbon or Charcoal)
15% is for S (Sulfer or Sulpher)
75% is for KNO3 (Potassium Nitrate)

Another thing, What about the + Sing ?
If you see for example this formula :
10:15:75/S:C:KNO3 +10%Dx
Then you have the following:
10% Sulfer
15% Coal
75% KNO3
And in addition of 10% of Dextrin
Thus, You will get a total of 110 not 100.

Hope this helps.

It should be done in parts as the second one adds to more than 100. Also the first formula is wrong:
Sulpur and charcoal are the wrong way round.

[BlackSky]

Thanks karlfoxman, The mistake has been corrected in the above post.

Edited by BlackSky, 21 February 2006 - 03:56 PM.

[Damp Squib]

If you want cheap accurate scales go to www.ukscales.com I got mine from them for about ?25 they arrived in two days with batteries and calibration weight and are accurate to 0.01g perfect for testing small batches of comp I could in theory mix as little as 1g of comp accurately,so my 10g test batches are extremely accurate,they will also go up to 100g

heres a link to the scales I have- great product!

http://ukscales.com/...&products_id=80

Edited by Damp Squib, 21 February 2006 - 09:02 PM.

[pendulum]

Going back to scales.

For pyro use, I bought some digital jewellery scales on eBay recently, described as accurate to 0.01g. Seller was olympiceyewear. Scales manufactured by Neva. The total inc. delivery came to just ?11.90.

They are very accurate.

They measure up to 50g (although the "up to 100g" version only costs a few quid more).
They come with a calibration weight.

I have just seen this thread and it gave me some better ideas on how to test it than what I already had. So I just went and tested it again.

To test it I measured a Duracell battery: 24.32g
And a metal bolt which weighed 21.02g
Adding that up, it comes to 45.34g

When I measured both on the scales at the same time, the reading was 45.35g - so that's definitely an acceptable margin of error! The +0.01 discrepancy could even have been caused by the sweat on my hands... I was sweating quite badly... who knows.

I also took an LED and measured its weight 3 times, turning the scale off and on inbetween each measurement... each time it came out as measuring the same.

And when measuring the calibration weight, which is 50.00g, it comes out as being 50.00g.

So I am very happy with these 'cheap' digital scales. They have turned out to be very accurate and a very good investment. Definitely would recommend getting a pair off eBay, ok, there is a small risk that you'll get a duff pair, but if you get a good pair you'll love them I think.

Edited by pendulum, 08 September 2006 - 04:30 PM.

[BrightStar]

Interesting that the 50g/0.01g scales are good... I might invest as they would be helpful for making small quantities of Flash.

I bought the DS-500 500g/0.1g balance last week from ukscales.com for only ?9.99 + VAT + P&P, about ?15 in total. It arrived within 2 days and works just fine. It always reads spot on 100.0g with one cal weight, 200.0g with two and spot on with a new ?2 coin, good enough for me.



More importantly, it will let me accurately lift 4" ball shells and big 3" cans

A quick note though that the scales are easily damaged by overload and ingress of oxidisers etc. My previous Satrue 250g/0.1g from Maplin only lasted a year, suffering both of these abuses.

Edited by BrightStar, 30 March 2009 - 09:48 PM.

[BrightStar]

Since lots of us here seem to have a bit of a thing about balances, I thought you might like to see this one that a colleague's research group recently bought:



Amazingly, this does 250g in 0.0001g (0.1 mg) increments! That's a precision 1/2,500,000 of its full scale deflection.

The thing reads out to a computer graph plotter in real time and is so sensitive you can watch minute changes to samples in real time. It would be fascinating to put some damp stars in to see how they dry (no chance BTW!)

Still, just so you know.... yours for only GPB ?4000 (about USD $7500)

and I was so happy with my +/- 0.1g...

Edited by BrightStar, 30 March 2009 - 09:49 PM.

[spanner]

Harbor Freight has their imported (read Chinese) digital scale for <$20/USD, delivered (in the US).

It's battery operated, 0-500g capacity, +/- .1g accuracy.

It weighs in grams, ounces, penny weight and has "tare" and counting functions.

See more at: http://www.harborfreight.com/

Drawbacks are a small platform (6 X 8.5cm) and non chemical resistance to acetone-type solvents.

[dr thrust]

just my luck,i didn,t read this section and in my haste ran out the door to argos and spent about £16 on some digital kitchen scales" 1g "accurate,cr@p cr@p cr@p!i tried a two pence and it give me three different answers! and then with nothing on the scale the reading was going up and down by its self don,t know what to do keep it for a thrust type scale for rocket motors or smash it up with a big hammer hmmm anyway thanks people for pointing me in the right " scales" direction!

[marble]

Ouch, i got my set of 500gm digital scales for $15 AUD. Not 100% accurate as it measures my 50g slot weight as 50.1g but its a bit dirty but its close enough.

Edited by marble, 10 July 2007 - 05:30 PM.

[pudi.dk]

Right now I have a 100g +/- .1g scale that I got from my grandfather.
It has served me well until I recently is building a 3" that I need to weight out and so far (still need loads of pasting) it weights much more than 100 g (it's a guess, all I get on the display is "EEEEE")

Keten sells a 2000g +/- .1g for 170 zl (61$) !!!
That's unbelievable cheap, however I am a bit suspecious.
Either it's the quality or else it's just that scales in Poland are cheaply mass produced

[dr thrust]

Right now I have a 100g +/- .1g scale that I got from my grandfather.
It has served me well until I recently is building a 3" that I need to weight out and so far (still need loads of pasting) it weights much more than 100 g (it's a guess, all I get on the display is "EEEEE")

Keten sells a 2000g +/- .1g for 170 zl (61$) !!!
That's unbelievable cheap, however I am a bit suspecious.
Either it's the quality or else it's just that scales in Poland are cheaply mass produced

would they ever turn up? you could always email him