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Machine Safety

Do you require 2 coded magnetic reed switches per gate to achieve CAT 4? by safetyproducts
Posted: 3 Apr 02

No.

Two electro-mechanical devices are required per gate because an electro-mechanical device is subject to mechanical fatigue.  To acheive a dual redundant circuit 2 limit switches are required incase 1 switch welds or remains in the gate closed position.  In the case of a coded magnetic reed switch, in conjunction with a fail-to-safe control relay, they are not suseptiple to mechanical fatigue and are not subject to over voltage as the fail-to-safe relay supplies the coded magnetic reed switches with 30mA which is isolated from the power supply.  This is my interpretation of AS4024.1.

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