Patent ID: 6885306

Claim:
A monitor for monitoring presence or absence of a liquid product in a system for pumping said liquid product from a supply through a pump and associated tubing to a destination, comprising: a capacitive sensor coupled to the outside of said tubing at a sensing location between said pump and said destination, said capacitive sensor being responsive to the presence or absence of said liquid product in said tubing; said tubing having an inside surface at said sensing location and having a volume within said tubing at said sensing location, said tubing being selected from a material and having an inside diameter at said sensing location selected such that: said material of said inside surface of said tubing and said inside diameter of said tubing being large enough such that said liquid product is substantially evacuated from said tubing at said sensing location when said liquid product is substantially absent from said tubing preceding said sensing location, and said inside diameter of said tubing being small enough and said material of said inside surface being selected such that air remaining in said tubing is substantially absent from said tubing at said sensing location when said liquid product is substantially present in said supply; said inside surface of said tubing and said liquid product being selected such that said liquid product forms a contact angle with said inside surface of said tubing at said sensing location of less than seventy degrees.