Wieland Electric has introduced its new SNS 4084K Zero-Speed Monitor safety relay which monitors the pulse frequency of sensors, such as inductive proximity switches or incremental encoders, safely switching off any dangerous movement when the limit frequency set on the device is exceeded.

The Zero-Speed Monitor can also control locking bolts in electric locking facilities, where access to dangerous machine parts is only provided when the machine movement is no longer a risk for the operator. The monitor is well suited to safety oriented retro-fits in existing machines and systems, and can be used with any machine drive technology.

The limit frequency to be monitored is adjustable between 0.1 and 99Hz and is set via two rotary switches. This is stored permanently in the device via a simple configuration process. Wieland’s Zero-Speed Monitor also has inputs for the implementation of a restart inhibit and a start override. This enables an electrical locking facility with locking bolts on a dangerous machine to be safely and easily controlled – even without a PLC.

The monitor is supplied with either pluggable screw terminals or spring force terminals, and can be used in applications up to PL e (Cat 4) according to EN ISO 13849-1 or SILCL3 according to EN 62061.