Operating instructions

Functions
5.12 Safety functions
CU240S and CU240E Control Units, FW 3.2
Operating Instructions, 03/2009, A5E02440075B AA
203
Debouncing and filtering the signals from the fail-safe input
As soon as a fail-safe input has been assigned to a safety function, the inverter checks the
consistency of the input signal. Consistent signals at both terminals always assume the
same signal state (high or low).
Reasons for inconsistent input signals
With electromechanical sensors (e.g. EMERGENCY STOP buttons or door switches), the
contacts may bounce briefly at the moment switching takes place. The two sensor contacts
never switch at exactly the same time either. As a result, the inverter responds with a fault
and indicates signal inconsistencies.
To prevent this, the input signals in the inverter must be filtered.
Figure 5-47 Debouncing and filtering the signals at the fail-safe inputs
Setting the signal filters in the inverter
Set the debounce time (P9650 and P9850) to such a level that faults caused by contact
bounce or signal faults cannot occur.
Note
Short response times are essential for ensuring the functional safety of machines. The filter
times increase the time required by the inverter to respond to fail-safe signals. For this
reason, do not set the filter times any longer than required.
Transferring the safety-relevant parameters
1. Click on the button to accept all of the settings that you have made.
2. If the default password has not been changed, you are prompted to change it.
3. In the following dialog box, confirm the checksums of the safety-related parameters. This
concludes the process of changing the safety settings.