Mitsubishi Q01CPU User Manual page 581

12
TROUBLESHOOTING
Condition
• Sneak path due to the use of two power
supplies.
Input signal is
not turned
OFF.
Stepwise distortion as shown below appears to
the zero cross voltage of input signal (AC).
Input signal is
not turned ON
(AC input
Zero cross
module)
voltage
False input Depending on response time setting, noise is
due to noise imported as input.
Cause
DC input
Input
E1
E2
module
E1 E2
<Calculation example of the resistance to be connected in Example 4>
• Connecting a switch with LED display, in which a maximum 2.33mA leakage
current flows when 24VDC is supplied to the QX40.
Leakage current
2.33mA
24VDC
• In this case, the circuit does not satisfy the condition that the OFF current of the
QX40 is 1.7mA or less. Connect a resistance as follows.
2.33mA
I =0.63mA
R
24VDC
Corrective Action
• Use only one power supply.
• Connect a sneak path prevention diode.
(Figure below)
E1
Improve input signal waveform by using the on-
line system etc.
Change the response time setting.
Example: 1ms to 5ms
(When excessive noise is cyclic, shorter
response time setting may produce a higher
effect.) When the above action does not have an
effect, take measures against noise to block
excessive noise, e.g. avoid tying the power
cables and control cables in a bundle, and add
surge absorbers to the noise sources such as the
relays and contactors used with the same power
supply.
QX40
Input
module
QX40
I =1.7mA
Z
Input impedance
R
5.6k
12.5 I/O Module Troubleshooting
12.5.1 Input circuit troubleshooting
DC input
Input
E2
module
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