Level control instrumentation - Rofi - #19

A magnetic switch contact consists of two flat contact tongues which are sealed in a glass tube filled with protective gas When approached by a permanent magnet, the overlapping contact tongue ends attract each other and spring into contact. When the permanent magnet is removed, the contact tongues demagnetize immediately and return to their rest positions as quickly as lightening. The air gap between

If a permanent magnet (a north pole red or a south pole blue) is placed near the actuating zone of the magnetic switch, the contact tongues of the built in protective gas contact are magnetized and attract each other. As the magnetic field between the contact ton­gues increases quadratically as the air gap becomes smaller, the magnetic switch contact springs back quickly to close position.

the contact tongue ends is only 0,2-0,3mm and the mass of the contact tongues to be moved and their elastic force are very small. Therefore, a magnetic switch switches almost inertia-lessly and it can be referred to as a «quas-electronic component .

A change-over contact has one movable and two static contact tongues. When there is no magnetic field, the movable contact tongue rests on the static home contact (break contact) by means of its elastic force.

By means of a polarizing magnet, a contact tongue is magnetized with a south pole field in such a way that when a permanent magnet north pole red is placed in its proxi­mity the magnetic switch contact closes and opens again when a permanent magnet south pole blue is placed in its proximity.

Change-over switch

Bue CD—Xf-l

Brown (2)_9

Back (3)

b1 ^ Rotœtiv

gas contact

1

Induc-r tance

Wire 1mm

d= 16 - 25mm l= 26 - 58mm

Operation of the magnetic switch with permanent magnets (or electromagnets) is completely free of wear and tear, as the magnetic field does not become worn out. As the contact tongues are extremely soft, fatigue fractures do not appear even after 3x10⁹ switching operati­ons (flections). If a magnetic switch was used once every second, then it would take hundred years to carry out 3 x 10⁹ (3 thousand million) switching operations. Its mechanical durability is therefore practically unlimited.

Magnetic switches operate impeccably under extreme environmental influences, for example dirt, moisture, gases, dust, shavings, etc.

Stable switch point, reproducible switch point exactness 0,01mm

Operable from several directions

Installation independent of position

Operable in a dead condition, bistable models can store

signals and are particularly suited for extremly long

strokes

Special types for extreme temperatures of -200C to +200C

Farticulary priceworthy component for automation

Magnetic switches are mainly used:

- as pulse generators for revolution, stroke and footage or meter counters, electromechanic counters

- running and stationary monitoring of machines

- as floor switches in elevators

- for resonant conveyors and sieves

- at weighbridges

- for the indication of end position of power cylinders in pneumatics

- in apparatus engineering for position indication of slides, flaps and valves

- for controlling machine tools

- for level control of fluids

- on textile machines, printing machines, and so on