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MELSEC-Q
9 TROUBLESHOOTING
9.3 The Module Does Not Count Pulses Correctly
Check item Action
Check the external wiring and correct the error.
Is the external wiring of
φ
A and
φ
B normal?
The module may miscount when ABCOM terminal is connected to
a pulse signal.
Connect the ABCOM terminal with external power (5V/12V/24V) or
GND terminal (refer to Section 4.4.2).
Is the maximum speed of input pulse within the range
of the counting speed made on the intelligent function
module switch setting?
Correct the counting speed setting in the intelligent function
module switch setting to meet the maximum speed of the input
pulse.
Does the input pulse waveform meet the performance
specifications?
Check the pulse waveform with synchronoscope. When the input
pulse does not meet the performance specifications, input the
pulse which meets the performance specifications.
Are the count value data handled in 32 bit-signed
binary in the sequence program?
Correct the sequence program so that the count value data are
handled in 32-bit signed binary.
Are the shielded twisted pair cables used for pulse
input wiring?
Use the shielded twisted pair cables for pulse input wiring.
Doesn't any noise come from the ground part of the
QD62(E/D)?
Separate the ground cable of the QD62(E/D) from the ground part.
When the QD62(E/D) case touches to the ground part, separate it.
Has the measures against noise been taken to the
adjacent devices and inside the control panel?
Take noise reduction measures (e.g. attach a CR surge
suppressor to the magnet switch).
Is the distance between the high voltage equipment
and pulse input line kept enough?
Bundle the pulse input lines and put them in a single tube, and
keep a distance of 150 mm (5.91 inch) or more with the power line
even inside the control panel.
Has the same count been input for both CH1 and
CH2 and are the count values the same?
If the count values are different, it is a hardware failure. Please
consult your local Mitsubishi representative.
Is the preset value, which replaces the present value,
within the count range of the ring counter? (This item
is for the ring counter function only.)
Set the preset value within the count range of the ring counter.