Float switches are simple, universally applicable and exceptionally reliable. It is not a coincidence that, today, float switches still represent the most commonly used principle for level monitoring. But how does pressure gauge octa work?
Float switches, in a simple mechanical form, have been completely in use for the control of water flows in mills and fields for centuries now still represent probably the most frequently used technology. A hollow body (float), due to its low density and buoyancy, lifts or drops with the rising and, respectively, falling degree of the liquid. If one uses this movement with a mechanical lever, e.g. as a simple flap control for an irrigation channel, one has implemented a mechanical float switch.
Modern float switches, needless to say, are used for switching a power circuit and feature a clearly more sophisticated design. In its simplest form, a float switch consists of a hollow float body with an integral magnet, helpful information tube to guide the float, adjusting collars to limit the travel of the float on the tube and a reed contact situated on its inside (see figure).
Figure: Collection of reed contacts of a float switch
So how exactly does the float switch function?
Reed contacts (see figure) of a float switch feature contact leaves within the hermetically sealed glass body, which move together or aside from each other whenever a magnetic field is applied. In the case of a float switch with a reed contact with a normally open function, on applying a magnetic field, the leaves are brought into contact. Once the contact between the leaves is made, a current can flow via the closed leaves and a switching signal will undoubtedly be detected.
Regarding a float switch with normally closed switching function, the contact or circuit is interrupted on applying a magnetic field. If one selects a change-over contact, the glass capsule will contain three contact leaves, with which, all the time, a normally closed and a normally open contact are simultaneously made in every operating state.
Because the contact leaves are under a mechanical preload, a magnetic field should be applied in order that the contact leaves close or open to be able to generate the required switching signal (monostability). The adjusting collars fitted by the product manufacturer serve as a limitation for the float body in the correct position, to make sure / keep up with the desired switching signal on reaching the defined filling level.
So how exactly does one specify a float switch?
The following parameters should be defined:
Number of switch contacts / switching outputs
Position and function of each switching output
Guide tube length
Electrical connection (e.g. PVC cable outlet)
Material (stainless steel, plastic, ?)
As a leading provider of float-based measurement technology solutions, WIKA has a wide variety of variants to meet all of your application-specific requirements. The available products can be found on the WIKA website. Your contact person will be pleased to advise you on the selection of the appropriate product solution.