Mitsubishi Electric MELSEC Q Series Programming Manual page 46

2 SAFETY OBSERVATION FUNCTION
PLC CPU
Safety signal
monitoring
comparison
External auxiliary
pulses
PLC IO
Shut-off
signal
The system configuration for speed monitoring function is shown below.
Speed
Mutual check
Consistency check
Safety signal module
(2) External auxiliary pulse input
(a) PLC CPU counts the number of leading edge of external auxiliary pulse
during speed monitoring, and check the consistency between the motor
feedback position from Motion CPU and the leading edge.
Refer to the "Q173D(S)CPU/Q172D(S)CPU Motion controller User's
manual" for input specification of external auxiliary pulse signal.
It is recommended to use the pulse generator achieves the safety
performance level required for system.
Contact the manufacture for the safety reliability data of pulse generator
Example of an external pulse generator for speed monitoring
Slit disk & Photo-interrupter
or Proximity sensor
(b) The input mode of external auxiliary pulse is the following.
Input mode and count timing are shown below.
Pulse input mode
1-phase mode
A-phase/B-phase mode
(2-phase multiple of 1).
Motion CPU
Speed
Safety signal
monitoring
comparison
Consistency
check
External auxiliary
pulses
Motion IO
Shut-off External auxiliary
pulse generator
signal
Incremental encoder
A-phase
A-phase
B-phase
A-phase
B-phase
2 - 9
Motor encoder data
Mechanical
attachment
A
B
Magnetic scale
Count timing
Up count by A-phase leading edge.
Up count by A-phase leading edge
when B-phase is OFF.
Down count by A-phase trailing
edge, when B-phase is OFF.
Safety
communication
compatible
servo amplifier
Servo motor/
safety encoder
Servo amplifier
Servo motor/
standard encoder