130BC316.10
Input Signal
DI1/DI2
D1 x A
D1 x B
Discrepancy time
Safety function
Active
Inactive
Illustration 3.3 Discrepancy Time
3.2.6
Stable Signal and Safety Devices
The safety option normally responds immediately to signal
changes at its safe inputs DI1 or DI2. This response is not
required in the following cases:
•
When interconnecting the safe input of the
option with an electromechanical sensor, contact
bounce may result in signal changes, to which
the option can respond.
•
Several control modules test their safe outputs
using test pulse patterns (on/off tests), to identify
errors due to either short- or cross- circuiting.
When interconnecting the safe input of the
option with a safe output of a control module,
the option can respond to these test signals.
A signal change during a test pulse pattern usually lasts 1
ms.
Under stable signal time, short pulses, which can lead to
safety functions being incorrectly activated, can be filtered.
NOTICE
The stable signal time extends the safety option
response time. The safety option only activates the
safety function after the response time has expired.
If the signal to the input on safety option is not stable, the
option responds with an external error after the stable
signal time expires.
Definition of a stable signal
Following a change to the DI input signals, the option
triggers an internal monitoring time. Use 42-23 Stable
Signal Time to select the appropriate stable signal time. A
stable signal is a high or a low signal state, which lasts for
the time defined in 42-23 Stable Signal Time.
Input Signal
130BC317.10
DI1/DI2
Safety function
Active
Inactive
Test pulse pattern
Stable signal time Stable signal time
Illustration 3.4 Filter for Suppressing Temporary Signal
Changes
Functions Safety Option MCB 152
12 Danfoss A/S © 10/2014 All rights reserved. MG37F102
33
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