Campbell CR23X, Operator'S Manual

Page: 53 / 374

SECTION 2. INTERNAL DATA STORAGE
2-3
2.2 DATA OUTPUT FORMAT AND
RANGE LIMITS
Data are stored internally in Campbell Scientific's
Binary Final Storage Format (Appendix C.2).
Data may be sent to Final Storage in either LOW
RESOLUTION or HIGH RESOLUTION format.
2.2.1 RESOLUTION AND RANGE LIMITS
Low resolution data is a 2 byte format with 4
significant digits and a maximum magnitude of
+6999. High resolution data is a 4 byte format
with 5 significant digits and a maximum possible
output value of +99999 (see Table 2.2-1 below).
TABLE 2.2-1. Resolution Range Limits of
CR23X Data
Minimum Maximum
Resolution Zero Magnitude Magnitude
Low 0.000 +0.001 +6999.
High 0.0000 + .00001 +99999.
The resolution of the low resolution format is
reduced to 3 significant digits when the first (left
most) digit is 7 or greater. Thus, it may be
necessary to use high resolution 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 ft., the level must be less
than 70 ft. for low resolution output to display the
0.01 ft. increment. If the water level was expected
to range from 50 to 80 ft. the data could either be
output in high resolution or could be offset by 20 ft.
(transforming the range to 30 to 50 ft.).
2.2.2 INPUT AND INTERMEDIATE STORAGE
DATA FORMAT
While output data have the limits described
above, the computations performed in the
CR23X are done in floating point arithmetic. In
Input and Intermediate Storage, the numbers
are stored and processed in a binary format
with a 23 bit binary mantissa and a 6 bit binary
exponent. The largest and smallest numbers
that can be stored and processed are 9 x 10
18
and 1 x 10
-19
, respectively. The size of the
number determines the resolution of the
arithmetic. A rough approximation of the
resolution is that it is better than 1 in the
seventh digit. For example, the resolution of
97,386,924 is better than 10. The resolution of
0.0086731924 is better than 0.000000001.
A precise calculation of the resolution of a
number may be determined by representing the
number as a mantissa between .5 and 1
multiplied by 2 raised to some integer power. The
resolution is the product of that power of 2 and
2
-24
. For example, representing 478 as .9336
∗
2
9
, the resolution is 2
9
∗
2
-24
= 2
-15
= 0.0000305.
A description of Campbell Scientific's floating
point format may be found in the description of
the J and K Telecommunications Commands in
Appendix C.
2.3 DISPLAYING STORED DATA -
7
MODE
(Computer/terminal users refer to Section 5 for
instructions on entering the Remote Keyboard
State.)
Final Storage may be displayed by using the
7
Mode. Key
7
.
If you have allocated memory to Final Storage
Area 2, the display will show:
Mode 07: Storage Area
00
Select which Storage Area you wish to view:
00 or 01 = Final Storage Area 1
02 = Final Storage Area 2
If no memory has been allocated to Final
Storage Area 2, this first window will be
skipped.
The next window displays the current DSP
location. Pressing
A advances you to the
Output array ID of the oldest Array in the
Storage Area. To locate a specific Output
Array, enter a location number that positions the
Display Pointer (DPTR) behind the desired data
and press the "A" key. If the location number
entered is in the middle of an Output Array, the
DPTR is automatically advanced to the first data
point of the next Output Array. Repeated use of
the "A" key advances through the Output Array.
Data and the alphanumeric label assigned by
EDLOG are displayed. The "B" key backs the
DPTR through memory.
The memory location of the data point is
displayed by pressing the "#" key. At this point,
another memory location may be entered,
followed by the "A" key to jump to the start of