Sartorius Mark III Moisture Analyzer

[jnewmanco1]

Anyone else using or at least familiar with this particular model? Ours will sometimes give very strange results and I am having a hard time figuring out what it's doing.
In the past I was told that if testing hot materials such as 250 degree dried polycarbonate, and you put this hot sample directly in the analyzer, it could give wonky results with - negative moisture percentages. So usually, if I am testing these hotter materials, I will let them cool in the sealed sample jar for 20 minutes or so and the tests seem to run normally.

Now I was running a test on some straight polycarbonate and for about the first 4 to 5 minutes of the test everything was looking normal. The weight of my sample was slowly going down and the displayed moisture level was slowly going up, when then all of a sudden, the moisture level jumped to -114%. It started going back towards normal but the end result was a FAIL on the test with my sample showing .125% moisture level. (0.020% or lower is acceptable)

I still had enough sample left in my jar so I ran a second test. This one ran seemingly fine and showed PASS with .014% moisture after 7 minutes of testing.

Any ideas or suggestions on what may be going on?

James N.

[Shearstressin me out]

We used to get negative moisture readings on our Sartorius machine due to the scale not being properly balanced.

If the scale/pan was tilted in the certain direction it would cause it to give off a negative reading.

You could also be running to high of a temperature burning off volatiles which could cause a negative reading.

[brentb]

Got weird results,QA thought resin was TOO cool????
KOM brent