Recently I was extraordinarily lucky and purchased a used Sartorius B120S balance for just $100, shown here:
However, during transit both the front and back glass draft shields were broken. Fortunately the function of the scale itself is unaffected and also
the sliding doors are undamaged. In the pic above you can see the cracked glass which I'd like to replace if possible. On the back at the top there
are some screws which must pass through holes drilled in the glass, this bit is easily undone and no issue. But at the bottom I find this:
Here is what my question revolves around - is the glass glued in place here or attached by some other means? Looking at it I am leaning towards
thinking it is glued as the rectangular plastic pieces shown do not appear to be easily removable. This is making me unsure how to proceed with
removal/replacement. I don't want to rush into this and cause more damage so I'm asking here if anyone has encountered a similar situation and what
did you do?
Swede - 31-7-2012 at 10:25
Replace the panels with perspex or acrylic. It'd be reasonably cheap and also something well within the capabilities of the home scientist.
Nice purchase, BTW.gutter_ca - 31-7-2012 at 10:32
Swede:
No static issues on an analytical balance with acrylic?Hexavalent - 31-7-2012 at 11:04
That's what I'd be worried about, gutter.
What readability does the balance have, and how is the linearity? Where did you find it?
Enjoy your investment
gutter_ca - 31-7-2012 at 12:26
The last time I had an analytical balance calibrated by an outside service, they used some sort of antistatic device. My google-fu is apparently weak
today, can anyone point me toward said device?Mailinmypocket - 31-7-2012 at 12:47
The last time I had an analytical balance calibrated by an outside service, they used some sort of antistatic device. My google-fu is apparently weak
today, can anyone point me toward said device?
Thanks, Mailin, the second one is what I had in mind.Endimion17 - 31-7-2012 at 13:21
Static is one problem. Heat is another one. Glass and acryllic have different heat capacity and thermal conductivity. When you measure in the 0.1
miligram range, the heat of the rising air can disturb the reading.
I think I'd just put some tape over the cracks.a_bab - 1-8-2012 at 13:33
Another quick dirty way is looking for some "Windshield Crack Repair Resin" used by the people who repair... cracked windshields: it has the
refractivity of glass, and the cracks will become (almost) invisible.
They will still stay on your brain (you'll know they are there) but that's another story.
[Edited on 2-8-2012 by a_bab]watson.fawkes - 2-8-2012 at 05:04
No static issues on an analytical balance with acrylic?
Static can be ameliorated by rubbing on a layer of
graphite. Put down a bit of graphite and rub with a smooth pad. You don't need much graphite; all you need is a few microns to get a conductive-enough
coating. Look up some of the online instructions on building electrostatic speakers for more details; this technique is used to make conductive mylar
sheet.
This works with glass, as well.Dr.Bob - 2-8-2012 at 09:53
I would agree on the glass part. We have had balances with minor cracks in them for years that worked fine. It is like a dent in a car, you can
fix it for enough money, but the car does not run any better, faster or more reliably. Or you can spend a lot to fix it and your wife dents it the
next week. Just put a piece of tape on it (on the outside if you are worried about static.)arsphenamine - 7-8-2012 at 09:10
Re: static electricity.
Cheapest:
Wipe down the glass/acrylic with a fabric anti-cling clothes dryer sheet.
Make an electrical ground for the balance case if there is none.
Expensive and potentially hazardous:
The Static Master Brush for photographic films uses Po-210 α radiation to control static.
Good points on the static... I hadn't even thought about that.
Quote:
Make an electrical ground for the balance case if there is none.
Place some foil strips on the balance, so that when the shield is in place, any charge built up could drain to ground. Obviously the foil strip(s)
need grounding as well.warteo - 8-8-2012 at 04:23
Thanks for the replies everyone. I'll most likely follow the advice to simply tape the outside. Was a little concerned about the potential safety
issue of the weakened glass but since the balance will be eventually set up for use in an area with minimal disturbances it should be just fine.
In retrospect I should have driven the 220km round trip to collect instead of assuming the seller would know how to correctly package a delicate item.
Lesson learnt for next time I purchase equipment on ebay.
