Electrical coffee maker with sensor in water by=pass - has indicator to show that the heater outlet pipe is furred-up by dissolved chalk

摘要

This electrical coffee maker has a cold water reservoir (1), connected to a heating chamber (3). The hot water is forced up the outlet tube (4) from which it runs through a filter holder (6) into the jug (7). The outlet tube (4) has a narrow by-pass tube (10) which has a very restricted opening (5) at the bottom. If the calcium salts in the water have caused excessive furring the opening (5) becomes blocked, and a detector electrode (11) in the top of the by-pass detects that the water in the by-pass does not run away. An indicator circuit (16) activates the detector (11) a short time after the level detector electrode (15) detects that the heating and syphoning process is over.