Mitsubishi MELSEC L Series User Manual page 118

(13)A rotation speed is not normally measured.
If a rotation speed is not normally measured in rotation speed measurement mode, check the following items.
An input pulse waveform does not meet the performance
specifications.
Shielded twisted pair cables are not used for pulse input
wiring.
Noise reduction measures are not taken in the control panel
or to adjacent devices.
Distance between the power equipment and the pulse input
cables is short.
Pulses are input at a speed faster than the speed configured
at counting speed setting.
If a rotation speed is not normally measured even after taking the above actions, the possible cause is a hardware
failure.
Please consult your local Mitsubishi service center or representative, explaining a detailed description of the
problem.
(14)Pulses are not measured.
If pulses are not measured in pulse measurement mode, check if CH1 pulse measurement start command
(SM1898) is on.
If pulses are not measured even if this relay is on, the possible cause is a hardware failure.
Please consult your local Mitsubishi service center or representative, explaining a detailed description of the
problem.
(15)Pulses are not normally measured.
If pulses are not normally measured in pulse measurement mode, check the following items.
Shielded twisted pair cables are not used for pulse input
wiring.
Noise reduction measures are not taken in the control panel
or to adjacent devices.
Distance between the power equipment and the pulse input
cables is short.
If pulses are not normally measured even after taking the above actions, the possible cause is a hardware failure.
Please consult your local Mitsubishi service center or representative, explaining a detailed description of the
problem.
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Check item
Check item
Action
Input pulses meeting the performance specifications.
Change the cables with shielded twisted pair cables.
Take noise reduction measures.
Install the pulse input cables alone in a duct and wire the
cables away from power cables by 100mm or more in the
control panel.
Input pulses at a speed slower than or equal to the speed
configured at counting speed setting.
Action
Change the cables with shielded twisted pair cables.
Take noise reduction measures.
Install the pulse input cables alone in a duct and wire the
cables away from power cables by 100mm or more in the
control panel.