Messtechnik Sachs Irinos IR, User Manual

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Irinos IR Users Manual © 2015 - 2016 Messtechnik Sachs GmbH, Germany
Application notes
11 Application notes
11.1 Incremental encoders 1Vpp or TTL/RS422
11.1.1
Referencing for absolute measurement
Incremental encoders are no absolute measuring devices. In order
to get absolute measurement values after start-up and after a signal
error, referencing is required. The Irinos-Box IR-INC provides the
following possibilities for referencing:
o
Referencing via index
The counter value is set to 0, if the index signal is passed.
o
Referencing via software:
The counter value can be set by software any time. It is possible
to set the value 0 as well as to any other value (in the valid value
range).
Both actions can be done via the opcode
opcSP
(0x35) of the
MscDll.
Please note that the Irinos-Box IR-INC can only provide the
technical possibility for referencing. Details depend on the respective
measurement procedure. Hence referencing must already be taken
into account in the planning phase. It is particularly important to
have a plan for referencing after an incremental encoder error.
11.1.2
Input frequency
The input frequency of the incremental signals (TTL / RS422) or the
signal period (1 Vpp) is limited. Details can be found in the
specifications for the respective Irinos-Box.
In most measurement applications the theoretical input frequency is
far below the limits. However, in reality it can be exceeded quickly
through jerky movements. Examples are:
o
“Cutting loose” at the beginning of a movement (crossing static
friction)
o
Mechanical stroke
o
Jerky movement due to mechanical tensions
It is recommended to take this into account during the planning
phase. If a jerky movement cannot be avoided, this must be
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