Capacitive fluid level detector for inking mechanisms - measures capacitance changes associated with collapsible container

摘要

The fluid level detector consists of a two section plastic housing (1), the inside walls of which are coated with a conductive layer (3) such as graphite or nickel. Inside the assembled housing is a collapsible bag (4) containing the fluid, e.g. ink, and connected via a stopper (16) to the outer wall of the housing. The inside of the bag is metallised and the connection brough tout via the outlet tube (8). The total capacitance of this arrangement is represented by C=Co.Cr. A/D where co is the dielectric constant of air, cr is the dielectric constant of the bag, A is the total area of the conductor (6) and D varies as the liquid level falls.