48
4 FUNCTIONS
4.9 Input Signal Error Detection Function
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Simple disconnection detection
Outputs an alarm when an analog input value is 0.5 V or smaller or 2 mA or smaller.
By the input range setting, simple disconnection detection is enabled. The simple broken wire detection is supported only in
the "4 to 20 mA" or "1 to 5 V" range. When an analog input value satisfies either of the following conditions, a disconnection
occurs and 'Input signal error detection flag' (Un\G40) turns on.
The settings for 'CH1 Input signal error detection lower limit set value' (Un\G529) and 'CH1 Input signal error
detection upper limit set value' (Un\G530) are ignored.
Notification
When an input signal error is detected, an error is notified as follows.
• Input signal error (1) is stored in the corresponding bit of 'Input signal error detection flag' (Un\G40).
• 'Input signal error detection signal' (Un\G69, b12) turns on.
• The ALM LED flashes.
• An alarm code is stored in 'Latest alarm code' (Un\G2). Alarm codes are stored whenever the analog input value satisfies
the condition for the input signal error detection. (
• The digital output value or digital operation value before the input signal error was detected is stored in 'CH1 logging data'
(Un\G10000 to 19999) depending on the 'CH1 logging data setting’ (Un\G536).
Operation
On the channel where an error is detected, the last digital output value and digital operation value just before the error was
detected are stored.
When the analog input value does not satisfy the condition of the input signal error detection, the A/D conversion resumes
regardless of off of 'Input signal error detection flag' (Un\G40) and 'Input signal error detection signal' (Un\G69, b12). (The
ALM LED remains flashing.)
• When an input signal error occurs, the digital output value and digital operation value are not updated.
• The A/D conversion continues on the channel where no Input signal error is detected.
• Whether an input signal error occurred is judged with the value when the first A/D conversion is completed.
Thus, the corresponding bit of 'A/D conversion completed flag' (Un\G42) turns on even when an input signal
error is detected.
Detection cycle
This function works at every sampling cycle.
Input range
Disconnection detection value
4 to 20 mA
Analog input value
≤
2 mA
1 to 5 V
Analog input value
≤
0.5 V
Analog input value
Time (t)
Error
detection
2 mA or 0.5 V
Summary of Contents for MELSEC iQ-F
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