Data Storage - Campbell CR300 Series Product Manual

Float Long integer is converted to a Boolean, zero is False (0), any non-zero value will set
or
the Boolean to True (-1). The Boolean data type allows application software to display it as an
On/Off, True/False, Red/Blue, etc.
The CR300 series uses –1 rather than some other non-zero number because the
operators are the same for logical statements and binary bitwise comparisons. The number -1 is
expressed in binary with all bits equal to 1, the number 0 has all bits equal to 0. When –1 is anded
with any other number the result is the other number, ensuring that if the other number is non-
zero (true), the result will be non-zero.
As String * size
with an optional size specifying the maximum number of characters in the string. A string is
convenient in handling serial sensors, dial strings, text messages, etc. When size is not specified,
a default of 24 characters will be used (23 usable bytes and 1 terminating byte).
As a special case, a string can be declared
single character. The string will take up 4 bytes in memory and when stored in a data table, but it
will hold only one character.

12.4.2 Data storage

Data can be stored in either IEEE4 or FP2 formats. The format is selected in the program
instruction that outputs the data, i.e. minimum, maximum, etc.
Float
While (IEEE 4 byte floating point) is used for variables and internal calculations,
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
vs 4).
Table 12-2: Resolution and range limits of FP2 data
Zero Minimum magnitude Maximum Magnitude
0.000
FP2
The resolution of
greater. Thus, it may be necessary to use
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
increment. If the water level is expected to range from 50 to 90 feet the data could either be
IEEE4
output in or could be offset by 20 feet (transforming the range to 30 to 70 feet).
specifies the variable as a string of ASCII characters, NULL terminated,
As String
±0.001
is reduced to 3 significant digits when the first (left most) digit is 8 or
IEEE4
* 1. This allows the efficient storage of a
±7999.
output or an offset to maintain the desired
FP2
output to display the 0.01 foot
AND OR
and
FP2
IEEE4
(2 bytes per value
12. Working with data
is
60