How can I calibrate my Ohaus cent-o-gram model 311 balance scale?

[tony873004]

I have a classroom full of Ohaus cent-o-gram model 311. Most work fine, but a few I can't calibrate to 0. I've used the calibration screw, but even maxed out it isn't enough. I could always place a couple of pennies under the tray, but there's got to be some way to do a course adjustment. Anyone?

 

[Simon Bridge]

I've used these a LOT.
Sounds like the shot is missing from underneath the pan.

See field service manual 3-3 B:
https://www.daigger.com/Portals/0/Literature/1260D_SM_OHAUS.pdf

 

[tony873004]

Thanks! I see what's going on now. I assumed they were all identical, and there would be no reason for factory-installed shot to go missing. But they're not identical. I didn't realize that each balance, its mass hanger, and its tray are all stamped with a matching 4-digit number. If you mix up the parts, you can run into trouble calibrating them. Now that I've put them all together by number, they all calibrate except one. Its parts do not have matching numbers. I'll just put some staples and paperclips in with the shot.

 

[Simon Bridge]

Cool - good catch for others resurrecting old equipment.
May be an idea to renumber or otherwise mark the odd one, for future generations, too.

 

[AlephZero]

I expect that somewhere you have another uncalibrated balamce, also made from non-matching parts.

Possibly this is a job for the Discworld minor goddess Anoia, responsible for Things that Stick in Drawers, Lost Cutlery, etc, ... and considering moving on to become Goddess of Hopeless Causes.
http://en.wikipedia.org/wiki/Discworld_gods#Anoia