Why Liquid Control? 

Lowering the pressure in the vacuum chamber causes liquids to boil. Even if they are cold. This is a law of nature. The Liquid Control sensor detects the evaporation that is released. Once boiling point is reached, the vacuum packing machine stops vacuuming and starts sealing. This prevents damage to the product and contamination of the chamber. It also avoids oxidation of the pump.    

Stops the vacuuming process when evaporation is detected. This prevents contamination of the chamber, oxidation of the pump, and dehydration and loss of weight
Liquid control