Recalibration of a 80g Scale with a 50g Weight

[quasar987]

I bought a 80g x 0.01g scale from ebay and it came with a 50g weight. Now this weight is exactly 50g up to more than 1mg, I suppose? But when I put in on, it read 50.08g. So the scale is off it seems. There are instructions to recalibrate the scale but it seems like the instructions are talking as if I had a 200g scale. It says "To recalibrate, turn on the scale, wait til it read 0.00. Push UCAL. Put a 200g weight on. Wait 3 seconds. Press UCAL. Switch off."

In any case, I have a 80g scale and it came with a 50g weight. Can I still recalibrate the thing with the 50g weight or I'm going to screw it up even more? (I tried asking the compagny that made the scale but no response)

thx

 

[chemisttree]

What brand of scale do you have? What does the 50 g standard weight look like? Does it have a shiny silvery appearance or is it painted?

 

[quasar987]

Hi chemisttree,

The weight is like this one: http://www.uptontea.com/shopcart/images/items/AR45-@DFL-200g+weight.gif

But there is a little defect on it... there is "50 g" carved on the top like in the picture, but the "g" is incomplete, so it resembles more a "q" than a "g". This probably means there is extra weight in the weight thatshould be there. Could that little missing branch in the "g" account for the 0.08±0.01g error?

The scale brand is Digital Scale E-S Series (it's a pocket scale). Design-wise it is exactly like this one: http://digitalscales.ca/MX50Gemscale.html

 

[chemisttree]

Until you calibrate the instrument at full scale, you won't get an accurate result. You weighed a 50 g weight and read 50.08 g. You should follow the calibration procedure for the 250 g instrument and substitute the 50 g mass. Tare the instrument with no mass on the pan and read the indicator with the 50 g mass on the pan. It should read 50.00 g unless the linearity is screwed up. Linearity is listed for the model you linked to at +/- 0.01 g. To confirm this you will need some more masses. See here for the method.

http://www.iescorp.com/linearity.htm

You might want to confirm that the instrument is on a level surface as well. There is probably no way to adjust the level on this small instrument. You might try small slips of paper if the level is off.

 

[Stevedye56]

If I was you and this happened. I would try to send it back and explain the situation to the seller. Hopefully you could at least exchange it for another one. I doubt that the missing part of the g is responsible for that much of an error but I bet that it could give you at least .01g-.02g maybe .03g but I doubt it would give you much more of an incorrect reading. Is there a hardware store near you with weights?