Mitsubishi Electric MELSEC iQ-F FX5 User Manual page 103

When the ALM LED turns on or flashes
■When turns on
Check item
Check whether any alert has been issued.
■When flashing
Check item
Check whether any input signal error has occurred.
When a normal digital output value cannot be read
Check item
Check whether there is any problem with the wiring, such as looseness or
disconnection of analog signal lines.
Check whether the CPU module is in the STOP state.
Check whether the offset/gain setting in the user range setting is correct.
Check whether the input range setting is correct.
Check whether the following Check whether the module is turned off and
operations are performed then turned on.
while the current on the
Check whether the A/D conversion enable/
negative side is applied.
disable setting is changed.
Check whether the range setting is
changed.
Check whether A/D conversion disable is set in A/D conversion enable/
disable setting of the channel where a value is to be input.
Check whether 'Operating condition setting request' (Un\G70, b9) has been
executed.
Check whether the setting value of the time average is correct when the
time average is selected in Averaging process specification.
Check whether there is any potential difference between the FG terminal
and the external device ground.
Check whether external devices to be connected at each channel share the
same ground.
Check whether the program for reading digital output values has an error.
Check whether the refresh setting is correct.
Corrective action
Check Alert output flag (Process alarm upper limit), Alert output flag (Process
alarm lower limit), Alert output flag (Rate alarm upper limit), and Alert output flag
(Rate alarm lower limit).
Take actions described in the list of alarm codes.
Page 106 List of alarm codes
Corrective action
Check Input signal error detection signal or Input signal error detection flag.
Take actions described in the list of alarm codes.
Page 106 List of alarm codes
Corrective action
Identify the faulty area of signal lines by a visual inspection and continuity check.
Change the state of the CPU module to RUN.
Check that the offset/gain setting is correct.
If the user range setting is selected, change the input range to the factory default
and check that the A/D conversion is performed.
If the A/D conversion is correct, perform the offset/gain setting.
Check the CH Input range setting monitor with GX Works3. If the input range
setting is incorrect, retry the input range setting.
Start up the module, and after 'A/D conversion completed flag' turns on, start
input from the external device.
Change the setting, and after 'A/D conversion completed flag' turns on, start
input from the external device.
Check CH A/D conversion enable/disable setting and set it to A/D conversion
enable using a sequence program or the GX Works3.
*1
Turn offonoff 'Operating condition setting request' (Un\G70, b9) and check
that a digital output value is stored in 'CH1 Digital output value' (Un\G400) using
GX Works3. If the stored value is correct, check the program.
When the time average is selected for processing, set the time average value in
CH Time average/Count average/Moving average/Primary delay filter constant
setting so that the value satisfies the following condition:
Time averaging setting value  4 (times)  Conversion speed  Number of
conversion enabled channels
If the condition above is not satisfied, the digital output value results in 0.
A potential difference may occur between the FG terminal and the external
device ground by a cause such as a long wiring distance, resulting in an
incorrect A/D conversion. Connect the FG terminal and the external device
ground to eliminate the potential difference.
If the external device ground is shared across channels, noise can sneak in
between channels, which may cause some error in A/D conversion. Connect the
FG terminal and the external device ground to eliminate the errors.
Check the CH Digital output values with GX Works3. If the digital output value
is stored without being converted from the analog input value, review and correct
the read program.
If the refresh is set so that the value in CH Digital output value is transferred to
the device of the CPU module, review and correct the auto refresh setting.
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1.10 Troubleshooting
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