Re: [Phys-L] Phys-l Digest, Vol 94, Issue 9

[Dan Beeker <debeeker@comcast.net>]

Just guessing. If a hardware problem the strain gauge on the balance 
beam may have been overstrained. Most balances use strain gauges glued 
to a "balance beam" There may be two strain gages wired in parallel. If 
the scale is overranged one leg of the strain gage could have broken 
causing a doubling of the resistance - hence twice the reading. Total 
conjecture on my part.

Or more likely, someone entered the calibrate mode by an arbitrarily (or 
intentionally) entered button sequence and did not finish the procedure 
causing some default values to be inserted. We have this happen 
occasionally with our lab balances. Students know strange things happen 
if they hit the right button combination. Makes an easy excuse - "The 
balance was broken" - when their lab doesn't work out.

 I would see if I couldn't find the calibration procedure and try 
recalibrating it.

Dan


On 10/10/12 12:00 PM, phys-l-request@phys-l.org wrote:
> Message: 1
> Date: Tue, 9 Oct 2012 14:30:51 -0600
> From: Larry Smith<larry.smith@snow.edu>
> To:<Phys-L@Phys-L.org>
> Subject: [Phys-L] digital balance on the fritz
> Message-ID:<C934942D-631C-4BFC-851C-641E784784CB@snow.edu>
> Content-Type: text/plain; charset="us-ascii"
>
> I have a VWF Sargent-Welch digital balance that has recently taken to reading exactly (to within 1%) double what it should (tested with calibrated masses).  Does anyone know how they work that would allow this to happen.  Broken I can understand, but then it just shouldn't work at all.  Broken in such a way as to read double what it should I don't understand.
>
> Thanks,
> Larry

--
Dan Beeker