Sartorius Mark III Moisture Analyzer

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.

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.

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