PC to update the info sector. The PC is much faster than the datalogger at
updating the info sector.
FAT32 uses an “info sector” to store the free cluster information. This info sector
prevents the need to repeatedly traverse the FAT for the bytes free information.
After a card is formatted by a PC, the info sector is not automatically updated.
Therefore, when the datalogger boots up, it must determine the bytes available on
the card prior to loading the Status table. Traversing the entire FAT of a 16 GB
card can take up to 30 minutes or more. However, subsequent compile times are
much shorter because the info sector is used to update the bytes free information.
Q: Which memory card should I use?
A: Campbell Scientific recommends and supports only the use of FMJ brand CF
cards. These cards are industrial-grade and have passed Campbell Scientific
hardware testing. Following are listed advantages these cards have over less
expensive commercial-grade cards:
• less susceptible to failure and data loss
• match the datalogger operating temperature range
• faster read/write times
• better vibration and shock resistance
• longer life spans (more read/write cycles)
Note More CF card recommendations are presented in the application note, CF
Card Information, which is available at www.campbellsci.com.
Q: Can closed files be retrieved remotely?
A: Yes. Closed files can be retrieved using the Retrieve function in the
datalogger support software File Control
(p. 515) utility, FTP, HTTP, or e-mail.
Although open files will appear in the CRD: drive directory, do not attempt to
retrieve open files. Doing so may corrupt the file and result in data loss. Smaller
files typically transmit more quickly and more reliably than large files.
Q: Can data be accessed?
A: Yes. Data in the open or most recent file can be collected using the Collect or
Custom Collect utilities in LoggerNet, PC400, or RTDAQ. Data can also be
viewed using datalogger support software or accessed through the datalogger
using data table access syntax such as TableName.FieldName (see CRBasic
Editor Help). Once a file is closed, data can be accessed only by first retrieving
the file, as discussed previously, and processing the file using CardConvert
software.
Q: What happens when a card is inserted?
A: When a card is inserted, whether it is a new card or the previously used card, a
new file is always created.
Q: What does a power cycle or program restart do?
A: Each time the program starts, whether by user control, power cycle, or a
watchdog, TableFile() with Option 64 will create a new file.
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