Magnetic Liquid Level Gauge

It consists of a chamber and an internal float in nonmagnetic material,
compatible with the liquid. The float containing a magnetic system, rides on
the liquid level and is coupled to an external visual indication, which comes in
two designs. The simpler and economical design consists of a RED magnetic
follower capsule, that moves within a glass tube filled with water (to reduce
friction) and can be read against a scale (fig. 1-a). The other system is
expensive and consists of a series of bicolour flappers, WHITE on front side and
a contrasting RED colour on the reverse. These flappers flip over corresponding
to float movement, thus changing their colour from WHITE to RED as the float
rises and changing back to white, when the float falls. As such, the liquid level is
represented by an external RED column (fig. 1-b). The accuracy of bicolour
flappers is limited by its width, however the follower capsule type does not have
this limitation.