Does moisture escaping from powders decrease chamber vacuum?

[Cleitus]

I'm drying some wet powders using vacuum oven and start seeing some condensation on the window after few minutes. The vacuum level stays pretty constant which puzzles me as i thought that the moisture escapes from the powder into the air will increase the chamber pressure or decrease the vacuum. I then put my logger in and found out that the relative humidity (RH) increases even though the chamber is at -0.1 MPa. Since the RH increases, how do i ensure that my powders are completely dry?

 

[Roark]

Out of curiosity, how does the RH meter you are using work? Is it supposed to work in vacuum?

 

[Cleitus]

Well the manual didnt specify whether it works under vacuum. Nevertheless, i went ahead and put it into check whether it logs the temperature and relative humidity. I can see the temperature stays pretty constant at 20˚C but the RH fluctuates depending on when I turn the pump on. At initial pumping, the RH drops and slowly increases after i stopped the pump. RH decreases again when i turned the pump on the second time. Btw, i placed a drop of water in a petri dish as an indicator assuming that when it dries out, my powders are dried.