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Error signal monitoring
The HS20 laser encoder continuously checks for internal errors that may cause invalid position
feedback signals, and signals a fault by asserting a tristated quad output. In the case of closed loop
motion systems, for safe operation the status of this tristated quad must be monitored. If the tristated
quad is asserted, the position feedback signals may be incorrect and the axis of motion must be
stopped.
Important note: In the event of power loss from the HS20, tristated quad become inactive and the
axis of motion must be stopped.
Incorrect bandwidth setting
The laser system allows you to adjust the maximum update rate of the digital encoder output signals.
If this is set too low (for the axis feedrate and resolution required) the laser system will flag when
overspeed error occurs. If the update rate is set too high, your controller may not be able to count
quickly enough to record all of the incoming pulses, and the axis may travel further than expected. It is
important that the output bandwidth of the laser system is set below the maximum input bandwidth of
the controller.
Laser alignment
If the laser beam is misaligned during beam alignment, the tristated quad will be asserted due to low
signal strength. Also, if the laser beam is misaligned such that the return beam enters the laser output
port, it is possible that the laser will be destabilised. This is normal behaviour, and again the tristated
quad may be asserted. In either circumstance, the laser position feedback signals may be invalid. For
this reason, initial beam alignment is usually performed with the machine under manual or open loop
control.
Power supply out of range
The correct power supply voltage is 24 V ±1 V. Power supplies outside this range may give unreliable
operation.
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