...what EDM stands for?


EDM stands for "External Device Monitoring” (feedback circuit). The safety relay monitors the feedback circuits of externally connected contactors with positively driven contacts. The signal at the EDM input is compared with the status of the safety outputs. When the safety output is switched on, the feedback circuit is open and when the safety output is switched off, the EDM input 24 V is connected. The NC contacts of the contactors with positively driven contacts are used to check whether the contactors have reached their safe state before they are actuated again. If a safety relay with manual reset function is used, the reset button is connected in series with the feedback circuit contacts.

 

contactor off

Figure 1: Safety sensor has shut down, Contactor are switched off, motor is off, 24 V is available at the EDM input

contactor on

Figure 2: Safety sensor is switched on, Contactors are switched on, motor running, no voltage present at the EDM input

 

 

EDM function of RFID safety sensor SAFIX 3

 

The SAFIX 3 safety sensor and the HOLDX R smart process guard locking have not only implemented state-of-the-art RFID technology, but also the full function of a safety switch device with EDM function. The SAFIX 3 / HOLDX R sensor can optionally be ordered with a manual or automatic reset function. Downstream contactors up to a current consumption of 500 mA can be connected directly to the safe OSSD outputs on the sensor. EDM- input monitors the externally connected contactors with positively driven contacts.

 

wiring SAFIX 3 A

 

Figure 3: EDM function with automatic reset button

wiring SAFIX 3 X

 

Figure 4: EDM function with manual reset button