The Liquid Level Controller (LLC) serves as a controller of the minimum or maximum liquid level in a solvent or waste bottle. It is possible to connect up to five LLCs in any combination on the control box. An open-collector output is activated with a time delay when the minimum or maximum liquid level has been reached. As an example, this output enables a running HPLC pump to be shut off.

The LLCs are made out of a glass body with two openings on the side for the liquid in and output. Located in the glass body is a “swimmer” made out of polyethylene (free of softeners). This swimmer carries a magnet on the upper taper. It is centrally led through a Teflon tube from the top. A reed contact is magnetically closed within the Teflon tube as soon as the swimmer reaches the surface or sinks to the bottom.

By closing the reed contact the control box is activated. The control box then turns the open-collector on and an acoustic alarm signal goes off. A periodic time can be set from 30 s up to 60 min inbetween the alarm signal and open-collector switch. This allows for adequate time to refill/empty the container and avoid the pump being shut off.

The Liquid Level Controller has two designs, one for overflow with a standard length of 150 mm and another for dry-cycle with a length of 240 mm. Custom lengths are available upon request. The control box is operated with a 9 V block battery.