The Count Operation Is Not Working; The Count Value Is Not Normal - Mitsubishi Electric QD62 User Manual

9 TROUBLESHOOTING

9.2 The Count Operation is not Working

Is the PLC CPU showing an error display?
Is the φ A and φ B external wiring normal?
When voltage is directly applied to the φ A and φ B pulse
input terminals, does the φ A and φ B LED light up?
Is the count enable instruction {Y04 (Y0C0)} ON?
Is the counter function selection start instruction {Y06 (Y0E)}
ON or is voltage being applied to the function start input
terminals?
Is an overflow error occurring?

9.3 The Count Value is not Normal

Does the pulse input method match the pulse input mode set
by parameter switch setting?
Is the maximum input pulse speed within the range of the
counting speed set by parameter switch setting?
Does the pulse waveform that was input meet the
performance specifications?
Is the count value data processed as binary 32-bit data in a
sequence program?
Does the pulse input wiring use a twisted pair shielded
cable?
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Is noise entering from the QD62 (E/D)'s grounding section?
Have noise preventive measures been taken inside the panel
and for adjacent equipment?
Is there sufficient clearance between high voltage equipment
and pulse input lines?
Has the same count been input for both CH1 and CH2 and
are the count values the same?
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Check item
Check item
Corrective action
If the PLC CPU is showing an error display, correct the
operation by following the troubleshooting instructions in the
manual for the PLC CPU in use.
Check and correct the external wiring.
If the LED lights up, check the external wiring and the pulse
generator side and make necessary corrections.
If the LED does not light up, this is a hardware error so
contact our branch office or distributor for consultation and
give details of the malfunction.
Turn the count enable instruction {Y04 (Y0C0)} ON using a
sequence program.
If the disable count function has been set with the counter
selection function, turn OFF the counter function selection
start instruction {Y06 (Y0E)} or the function start input
terminal.
Preset to clear the overflow error.
Corrective action
Match the pulse input method and the pulse input mode set
by the parameter setting switch.
Change the counting speed set by parameter switch setting
so that it is in line with the maximum input pulse speed.
Check the pulse waveform by observing it with a
synchroscope, and input the correct waveform pulse if it does
not conform to the performance specifications.
Change the sequence program so that the count value data
is processed as binary 32-bit data.
Use a twisted pair shielded cable for the pulse input wiring.
Separate the QD62 (E/D)'s ground cable.
If the QD62 (E/D) case is contacting the grounding section,
detach it.
Take noise preventative measures such as attaching a CR
surge suppressor to a magnet switch.
Wire the pulse input line independently inside the panel,
separate the pulse input line from the power line by at least
150 mm (5.9 in.).
When the count values are different, this is a hardware error.
Contact our branch office or distributor for consultation and
give details of the problem.
MELSEC-Q
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