It is necessary to understand how the PLC manages log files in case the SD card needs to be replaced by a different SD card during logging. When a different SD card is inserted during logging, the PLC does not know how much space has already been used because the PLC does not check the contents of the SD card. This may lead to data being lost.
The PLC tracks the following information about the logging files:
Every time specified records are stored, the PLC writes the data into the currently uncompleted logging file "%specified file name% (------current------).csv".
The PLC internally counts the number of completed files. The PLC does not check the number of files on the SD card.
The PLC internally stores the date of when a file is completed.
If you need to replace the SD card, clear the internal file management information and check that the new SD card is empty.
The internal information about logging files is cleared in the following cases:
When LOGn settings are deleted or all log settings are initialized in Control FPWIN Pro7.
When a buffer allocation that is different from the stored buffer allocation is downloaded, all log settings are initialized.
When a LOGn definition that is different from the stored data is downloaded, only the different LOGn is cleared.
If you plan on clearing the log file management information on the PLC, delete the files on the SD card or move them to a different location if you want to use them later. When the log file management information is cleared, the PLC no longer has any information about the number of files on the SD card and which is the oldest file. Clearing the log file management information does not delete existing files on the SD card, which leads to a discrepancy between the real amount of data on the SD card and the amount of data assumed by the PLC to be on the SD card.
When you restart logging without having changed the configuration, the PLC continues the logging operation with the previous system information, i.e. the number of files on the SD card and the name and time of the oldest file are kept.