Extra safety functions for speed monitoring modules

The first advantage of this development is that the PNOZmulti can now be used to monitor for broken shearpins on applications such as hoists. Previously this might have required two encoders to be used - one on the motor and one on the driven shaft - to check for any speed differential, but the new speed monitoring modules can perform this function much more easily and at a lower cost. This is achieved by means of the usual encoder on the motor and a PNP sensor on the driven shaft. Software running on the PNOZmulti base unit analyses the signals from these two devices and initiates appropriate action in the event of a broken shearpin being detected.

One notable feature of this enhancement is that it allows the PNOZmulti and speed monitoring modules to be used for economical safety-related control systems conforming to the requirements of BS EN 954-1 Category 4.

The second new function added to the speed monitoring modules and software is a time delay for over-speed tripping on start-up. Some machines with high inertial loads will typically over-speed on start-up, before quickly settling back to their normal running speed. To avoid the speed monitor identifying this as a fault condition, the Configurator software can now be used to set an over-speed detection time delay following start-up.

Two versions of speed and standstill monitoring module are available for use with the PNOZmulti controller. While the PNOZ ms1p operates with a 5V encoder, the PNOZ ms2p accepts any incremental encoder input with a differential output from 0.5-30V, which gives machine designers a wider choice of encoders and makes it easier to upgrade existing machines on which encoders are already installed. Note that version 2 speed and monitoring modules must be used in order to perform the new functions, and the Configurator software must be version 5.1.0 or later.

For more information about the PNOZmulti safety controller visit the website at www.pilz.co.uk.