Campbell Scientific CR1000 Measurement and Control System - Manual (Page 270)

Section 7. Installation
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• 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: Why not use SD cards?
A: CF cards offer advantages over Secure Digital (SD) cards, including
ruggedness, ease of handling, and connection reliability.
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. 454)
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.
Q: What happens when a card is filled?
A: If the CF card fills, new data are written over oldest data. A card must be
exchanged before it fills, or the oldest data will be overwritten by incoming new
records and lost. During the card exchange, once the old card is removed, the new
card must be inserted before the data table in datalogger CPU memory rings
2 , or
data will be overwritten and lost. For example, consider an application wherein
the data table in datalogger CPU memory has a capacity for about 45 minutes of
data
3 . The exchange must take place anytime before the 45 minutes expire. If the
exchange is delayed by an additional 5 minutes, 5 minutes of data at the beginning
of the last 45 minute interval (since it is the oldest data) will be overwritten in
CPU memory before transfer to the new card and lost.
1
Other options of TableFile() do not pre-allocate memory, so they should be avoided when
collecting high-frequency time-series data. More information is available in CRBasic Editor Help.