A.3 System Precision And Reaction Time - Festo CAMC-G-S3 Manual

A Technical appendix
A.3 System precision and reaction time
The following sections view the system precision requirements of functional safety engineering, with
regard to safely monitoring movement functions for position and speed.
The achievable system accuracy is primarily dependent on the system structure, consist­
ing of: Motor – Gear unit – Axle
It can be increased particularly through the use of a gear unit or through the selection of
an axle with a lower feed (è Section A.3.7, Tab. A.35).
The specified accuracies and reaction times of the safety module always represent a compromise
between:
– the resolution and the accuracy of the connected position transmitters and the allocated electronic
evaluation unit in the safety module,
– the desired high precision for the monitoring of the limit values for position and speed,
– the reaction time until the violation of a condition is detected,
– the system availability during operation in an industrial environment (malfunctions, EMC, etc.).
For this reason, the accuracies and reaction times should be as high as necessary from a safety point
of view, but not excessive.
Please note
The factory settings of the safety module for encoder analysis, speed detection and
position monitoring are correct for most applications. They are adapted to the resolu­
tion of the position encoders and to the electronic evaluation unit in the safety module.
They should only be changed when there are problems, as they influence the reaction
time of the safety module when dangerous movements are detected or during error
detection. They are so-called "Expert parameters".
Alternatively, check to see if the mechanical system can be changed (e.g. axle with
reduced feed).
Use the data transfer (è Section 2.3) to ensure that the safety module has the correct
parameters for the feed constant and the gear ratios, before you parameterise safety
functions.
260 Festo – GDCP-CAMC-G-S3-EN – 1406NH – English