Campbell CR9000, Instruction Manual

Page: 107 / 218

Section 6. Data Table Declarations and Output Processing Instructions
6-19
The source value may be the result of a measurement or calculation. Each time
the data table with the Level Crossing instruction is called, the source is
checked to see if its value has changed from the previous value and if in any
change it has crossed any of the specified crossing levels. The instruction can
be programmed to count crossings on either the rising edge (source changes
from less than the level to greater than the level) or on the falling edge (source
changes from greater than the level to less than the level).
0
0.5
1
1.5
2
2.5
3
3.5
0 1 2 3 4 5 6
FIGURE 6.4-1. Example Crossing Data
As an example of the level crossing algorithm, assume we have a one
dimension 3 bin level crossing histogram (the second dimension =1) and are
counting crossings on the rising edge. The crossing levels are 1, 1.5, and 3.
Figure 6.4-1 shows some example data. Going through the data point by point:
Point Source Action Bin 1
(level=1)
Bin 2
(level=1.5)
Bin 3
(level=3)
1 0.5 First value, no counts 0 0 0
2 1.2 Add one count to first
bin, the signal crossed 1 1 0 0
3 1.4 No levels crossed, no
counts 1 0 0
4 0.3 Crossed a level but was
falling edge, no counts 1 0 0
5 3.3 Add one count to first,
second, and third bins,
the signal crossed 1, 1.5
and 3. 2 1 1
The second dimension, when greater than 1, is determined by the value of the
element in the source array following the element checked for the crossing. It
is the value of this variable at the time the crossings are detected that
determines the second dimension.