|
Hasco Component's Reed Switches are meant for long life.
Each Reed Switch has an extremely long life. More important
is the fact that each reed switch can sit idle for years
without contact resistance build up. Ideal applications for
reeds include liquid level sensors, magnetic contacts, proximity
reed devices and reed relays.
HIGH RELIABILITY SUPPORTED BY UNIQUE TECHNOLOGY
Deactivated Rhodium Contact:
OKI reed switches are highly reliable because rhodium is
used as the contact material. Rhodium has two excellent
features as the contact material: Extreme hardness, which
improves the resistance against sticking; and a high melting
point, which greatly reduces the contact surface consumption
due to Joule heat or arc discharge affected by the current,
and also improves the resistance against sticking. However,
being a platinum metal, the surface of rhodium has active
absorption and catalytic actions. Rhodium plating greatly
absorbs organic impurities and forms a polymer in the course
of operation, increasing contact resistance as shown in
Fig. 21. This is especially noticeable a lower load level
operation. OKI has developed a unique oxygen treatment
method to deactivate the rhodium surface, in which organic
impurities adhered to the surface
are burned with oxygen and oxygen molecules are selectively
absorbed to produce a stabilized contact resistance. This
unique method won the highest prize (Schneider Award) on
the occasion of the 21st Annual National Relay Conference
held in Oklahoma, U.S.A. in 1973. Patents have been obtained
not only in Japan (Pat. No. 916386) but also in U.S.A. (Pat.
No. 3857175) and West Germany (Pat. No. 2303587).
Automatic Sealing:
Sealing, the moment when a pressed and plated reed contact
and a glass tube are united to form a reed switch,
is the most important stage in the manufacturing process
requiring strict control of conditions. At this stage, the
working temperature reaches approx. 1,000°C causing evaporation
of impurities from the glass tube and contamination and damage
of the contact part of the reed switch. To prevent this,
OKI has imposed severe standards on the selection of materials, and established a unique automatic sealing method. By thus
improving the
manufacturing process, OKI is able to produce reed switches
of the highest quality.
Flux Scanning Method:
In spite of severe control of the sealing process, there
is a slight probability that foreign matter such as magnetic
particles may enter the glass. After extensive study in
the detection of micro impurities, OKI has adopted the
highly reliable flux scanning method. In flux scanning,
as shown in Fig. 22, external magnetism is moved so that
foreign matter near the reed is forced to jump to the contact
part. The contact resistance then measured is used as the
standard for the selection of characteristics. We have
thus succeeded in remarkably improving the reliability
of reed switches by replacing conventional visual checking
with the latest flux scanning method.
Fig. 21
 |
Fig. 22
 |
|
