What Is Redundant Output? The Story Behind Dual-Channel Safety Design

Redundant output means the same measured position is given simultaneously by two independent sensing channels, for use in functional-safety-related applications. When one channel fails, the other can still provide position information, avoiding a single-point fault that would leave the machine uncontrolled. Germanjet's Series 16R redundant in-cylinder type uses this dual-channel design.

What redundancy is

Redundancy is not simply "dual output", but two measuring chains that are physically and electrically independent of each other: each has its own waveguide/magnet sensing, independent electronics head, independent supply and independent output. The system can compare the two readings in real time; once deviation exceeds a threshold or one channel fails, it alarms or switches at once to keep a safe state.

Functional-safety background

Where the consequences of failure are severe (for example metallurgical presses and large hydraulic presses), safety-related control is required to reach a given SIL (safety integrity level). Redundant measurement is one common means of meeting SIL requirements, together with a safety PLC to achieve fail-safe behaviour. See how to read functional safety SIL.

Implementation and comparison

Engineering notes

• The value of redundancy lies in "independence"; sharing a supply or sharing a magnet between the two channels weakens safety;
• Site redundant installation and comparison checks are in redundant installation;
• Redundancy does not equal higher accuracy; it is safety redundancy, not accuracy redundancy.

Hydraulic-cylinder safety application background is in hydraulic cylinder position control; multi-magnet is "multiple positions", not "redundancy" — a different concept (see multi-magnet measurement).