Diagnosable digital inputs for SMCS
Diagnosable digital inputs for SMCS
Diagnosable inputs, which recognize errors such as "short circuit to UB", "open load" and "short circuit to GND", are indispensable for safety aligned controls with PL d according to EN IEC 13849 or SIL-2 according to ISO 61508. This diagnostic capacity is already provided with the specification for classic 4 - 20 mA analogue entries: The analogue input has the required interface to detect the mentioned errors. Digital inputs, however, in their standard design only recognize the logical status of “0” and “1”.
Hirschmann Automation and Control GmbH, branch office Ettlingen, offers a solution to this problem.
The Scalable Mobile Control System (SMCS) with specialised, diagnosable digital inputs provides the reliable diagnosis of:
Short circuit to UB
Open load
Short circuit to GND
Two different models are available: the DI-DIAG for potential-free end switches and the DI-NAMUR for inductive and capacitive proximity switches with a NAMUR output. Furthermore, each input is tested periodically with a self test signal (test HS) on operation. All diagnosis data is available as variables to the user and can be analysed in the control program if necessary.
An external resistance circuit has to be provided for the DI-DIAG input which works from 9 to 48 VDC (+UB). This is partly already integrated into the end switches e.g. in iSENS HES A2B switches made by Hirschmann.
DI-NAMUR inputs area available for proximity switches (e.g. inductive, capacitive) with NAMUR output. They are EN 60947-5-6 conform and consider the defined voltage and power thresholds.
All DI-DIAG and DI-NAMUR digital inputs are also protected against over-voltage and can be used as security-relevant in/outputs.
CONTROL unlimited
July 2009