Specifications

Section 2. Data Storage and Retrieval
2.2 Internal Data Format
TABLE 2.2-1 CR3000 DATA TYPES
Data Type Size Range Resolution
LONG 4 bytes -2,147,483,648 to +2,147,483,647 1 bit (1)
IEEE4 4 bytes 1.8 E -38 to 1.7 E 38 24 bits (about 7 digits)
FP2 2 bytes -7999 to +7999 13 bits (about 4 digits)
Boolean 4 bytes True/False —
String 1 byte per character
+ 1 byte, 16 byte minimum
— —
Data are stored internally in a binary format. Variables and calculations are
performed internally in IEEE 4 byte floating point with some operations
calculated in double precision. There are six data types used to store data. The
data format is selected in the instruction that outputs the data. Within the
CR3000, time is stored as integer seconds and nanoseconds into the second
since midnight, the start of 1990. While IEEE 4 byte floating point is used for
variables and internal calculations, FP2 is adequate for most stored data.
Campbell Scientific 2 byte floating point (FP2) provides 3 or 4 significant
digits of resolution, and requires half the memory space as IEEE 4 byte
floating point (2 bytes per value vs. 4).
TABLE 2.2-2. Resolution and Range Limits of FP2 Data
Zero Minimum Magnitude Maximum Magnitude
0.000 ±0.001 ±7999.
The resolution of FP2 is reduced to 3 significant digits when the first (left
most) digit is 8 or greater (Table 2.2-2). Thus, it may be necessary to use
IEEE4 output or an offset to maintain the desired resolution of a measurement.
For example, if water level is to be measured and output to the nearest 0.01
foot, the level must be less than 80 feet for low-resolution output to display the
0.01-foot increment. If the water level is expected to range from 50 to 90 feet
the data could either be output in high resolution or could be offset by 20 feet
(transforming the range to 30 to 70 feet).
TABLE 2.2-3 FP2 Decimal Location
Absolute Value Decimal Location
0 - 7.999 X.XXX
8 - 79.99 XX.XX
80 - 799.9 XXX.X
800 - 7999. XXXX.
2.3 Data Collection
Data can be transferred into a computer via a communications link using one
of Campbell Scientific’s datalogger support software packages (e.g., PC200,
PC400, LoggerNet) or by transferring a CF card from the CR3000 to the
computer.
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