LINEPULS & LINECOD catalogue 2016 in English

LINEPULS
Output signals
SMEx1 linear encoders can be equipped with an additional PWM error output to signal fault
and error conditions to a PLC or a controller. The electronics generates a pulse-width modulated
(PWM) waveform signal with four different duty cycles. When the encoder falls into
error mode the diagnostic PWM signal is output. The duty cycle of the signal will depend on
what caused the encoder to enter the error mode. A frequency error -that’s to say: when the
encoder is travelling too fast along the tape- will cause a 50% duty cycle to be generated.
A distance error -i.e. when the specified mounting tolerances are not met- will cause the
diagnostic feedback signal to be at 75% duty cycle. Internal electronics error conditions will
cause a 100% duty cycle to be generated, so the signal will be at high logic level solidly.
On the contrary a low logic level (0% duty cycle) will indicate that no error is active.
PWM error output (on request)
PWM error output characteristics
Output signal
Duty cycle D 0%
LOW (0Vdc)
Duty cycle D 50%
Duty cycle D 75%
Duty cycle D 100%
HIGH (+Vdc)
No error is active.
Meaning
Frequency error: the sensor is
travelling too fast.
Distance error: specified mounting
tolerances are not met.
Internal error.
The series available with PWM error output on demand are: SME11, SME21, SME51.
The edge distance feature only applies to the
incremental digital signals and has to be selected
under the option EDGE DISTANCE in
the order code. It can be defined as the minimum
spacing time between two following
signal edges at output. The value is expressed
in μsec and calculated referring to all edges.
When choosing the resolution of the encoder
and its related minimum edge distance, consider
attentively also both the travel speed of
the application and the max. frequency that
the subsequent electronics is able to evaluate.
Edge distance
Unexpected situation with high travel speed to be considered are:
• micro-vibrations;
• heavy accelerations and decelerations.
Signals will be output at the highest speed (see the edge distance value charts) when the
sensor comes to a standstill exactly on a graduation mark, resulting in a frequent change of
the output signal by +/- 1 increment.
Please note that the minimum edge distance value is in relation with the max. speed value.
For slower speeds the effective edge distance is necessarily greater.
Also the max. mechanical travel speed indicated in the datasheet has always to be considered
attentively. It attests a mechanical permissible limit of the unit.
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