As electronic circuitry becomes more sophisticated and, in many cases, integrated into tiny complex sub-circuits, the problem of providing protection has to be addressed correctly and somewhat differently to original thinking. Many years ago, in the 1950s, Metropolitan Vickers developed the Metrosil - a metal oxide device which acted as a high resistance to normal voltage and a low resistance to high voltages. This ultimately became further developed and known as the metal oxide varistor (MOV).
MOV provides protection against high-voltage, high-frequency surges, such as those induced by lightning. Today's electronic equipment operates at very low voltage levels and may be subjected to transient voltages at lower frequencies - not necessarily high voltages - induced by, for example, switching or intermittent interruptions caused by a faulty connection. Silicon avalanche diode (SAD) technology was developed as an answer to this problem. SAD devices provide protection against high-power, low-voltage, transient peaks, including protection for themselves and have a high-performance reliability.
The ideal protection arrangement to safeguard against all hazardous possibilities across the voltage spectrum would seem to be a combination of MOV and SAD. The Atlantic Scientific Corporation in Florida realised the importance of this and produced the ZoneMaster SM series which combines MOV and SAD technology in one modular cost-effective package. The ZoneMaster series of surge protectors being modular can be provided for surge protection of any type of circuitry from a normal voltage distribution system, through to the protection of equipment such as computer, data communication and radio installations and the like, at the power-input point.
Atlantic Scientific Corporation, which is represented throughout southern Africa by Hellermann Tyton, produce over 800 surge protection devices. Confidence is such that they all carry a 10-year unconditional warranty. In the event that any component or subassembly within the unit fails to perform as specified during the 10-year period, a new replacement unit will be supplied free of charge (installation, labour and site preparations excluded).
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