Mitsubishi MELSEC Q series User Manual page 72

(d) When other functions are used
When the following functions are used, the data sampling performance of data logging is deteriorated.
• Project data batch save/load function (applicable to the LCPU only)
• iQ Sensor Solution data backup/restoration function
Therefore, data missing may occur even with the data logging settings with which it did not occur previously.
Also, with a setting with which data missing occurred previously, the frequency of data missing may increase.
● Once missing occurs, it tends to recur afterward. The following settings can reduce frequency of missing.
• Increase the sampling interval. ( Page 115, Section 8.4.4)
• Decrease the number of sampled data. ( Page 117, Section 8.4.5)
• Increase the buffer capacity. ( Page 135, Section 8.5.2)
• Decrease frequency of file switching. ( Page 127, Section 8.4.12)
• Cancel the "File Transfer" setting in the data logging setting. ( Page 129, Section 8.4.13)
To consider the processing time taken to data logging, refer to  Page 161, CHAPTER 10.
● When sampling cannot be completed within the specified sampling interval due to execution of an instruction of which
processing time is long (such as the FMOV instruction), it is not regarded as data missing.
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