Table of Contents
4.5
Connecting position and speed sensors
4.5.1
General notes
The SI-Safety module provides two sensor interfaces to enable connection to industry
standard incremental and absolute encoders. The encoder interfaces can be configured
as incremental, SIN/COS, or absolute SSI sensors.
In addition, connection to other sensors which generate incremental signals (i.e.
proximity switches) to input E0.5 of the SI-Safety module are also possible.
An encoder adapter module is available from Control Techniques to simplify the
connections of the encoders. If a single SinCos or incremental encoder is used then the
encoder signals must be connected to both encoder 1 and encoder 2 connections on
the HDMI cable.
The power supply to the sensor system can be connected via the terminal specified on
the SI-Safety module. This voltage is directed to the sensor connector where it is
monitored by an internal diagnostic process.
WARNING
If the sensor receives its power from an external source, that voltage needs to be routed
via the sensor connector. This allows the corresponding terminal (sensor power supply)
on the module to remain free.
If an external sensor power supply is not routed back through the sensor connector, any
failure of this power supply needs to be incorporated in the fail-safe arrangements for
the system as a whole. In particular, verification is required that this fault can be
detected and/or eliminated whenever the power supply to the sensor system is either
above or below specified limits.
The external power supply must meet the requirements of PELV/SELV.
•
When a single encoder is used the SI-Safety module employs two methods of
NOTE
evaluating the encoder signals. If the difference between the two evaluations
exceeds the threshold then an alarm will be produced. Appropriate measures must
therefore be taken when connecting the encoders to minimise any electrical
interference otherwise intermittent alarms could be triggered. It is advisable to
follow the EMC guidelines in the Unidrive M Drive User Guide.
•
Consideration should be given to EMC measures including layout, shielding and
shielding.
•
Both sensors must be free of reciprocal feedback, i.e. each must function
independently of the other. This applies equally to the electrical and mechanical
sections.
•
If both sensors are linked via shared mechanical components to the monitoring unit,
that connection must be configured for positive contact and must not include any
component parts which may be liable to wear i.e. chains, toothed belts etc. If such
parts are included, additional monitoring units will be required for the mechanical
connection between the sensors (e.g. monitoring of a toothed belt).
•
For active position processing purposes, at least one absolute encoder must be
used.
•
When using two equivalent sensors, always ensure that the sensor with the higher
resolution level is configured as Sensor one (process sensor), while the sensor with
the lower resolution level must be configured as Sensor two (reference sensor).
•
If the appropriate measures to reduce electromagnetic interference are not correctly
implemented the spurious speed difference/position difference trips may occur. This
is more likely if the speed is below 10 rpm.
38
SI-Safety Installation & Operating Manual
Issue Number: 1
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