Abstract: A liquid level detector includes an electrode portion including a substrate, a first electrode plate separated a predetermined distance from the substrate, a hollow second electrode plate extending from the substrate to the first electrode plate and having an opening corresponding to the outer circumferential surface of the first electrode plate, and a liquid level detecting portion which detects the presence of the liquid at the detection position from a change in electrostatic capacity measured by the first and second electrode plates. Thus, the level of liquid stored in the container can be detected from outside of the container in a non-contact manner, simplifying the structure of the apparatus and preventing the generation of an error in measuring the liquid level due to ink adhering to the container.

Abstract: An apparatus for measuring the concentration of developer in a liquid printer, the apparatus includes a housing, a developer film forming device installed in the housing for forming a developer film, and a sensing device including a light source unit for emitting colored light corresponding to a range of wavelengths for which the light transmissivity is relatively low to a developer film of a selected color developer, and a photodetector installed corresponding to the light source unit and receiving the light emitted by the light source unit and transmitted through the developer film. Thus, a thin developer film is formed and the concentration of developer is measured by emitting light in a range of wavelengths for which the selected color developer has a relatively low light transmissivity to the developer film. The affect by the toner mixed with other color is relatively less and the concentration of developer can be measured close to the actual concentration although the developer is contaminated.

Abstract: A method for easily notifying a user of the printing status of a color video printer by displaying the printing status of the color video printer. In order to display the color being printed, a pedestal level signal and a white level signal are multiplexed in response to a pulse width converted control signal. The multiplexed signal and a chrominance signal are applied to multiplex the chrominance signal in response to a selection control signal, and a multiplexed chrominance signal is displayed on a screen of a monitor by stimulating the screen monitor with an additive mixture of color so as to display the printing status.