Campbell Scientific CR23X Micrologger - Manual (Page 186)

SECTION 11. OUTPUT PROCESSING INSTRUCTIONS
11-6
the burst mode. The Rainflow Instruction can
process either a swath of data following the
burst mode, or it can process "on line" similar to
other processing instructions.
The output is a two dimensional Rainflow
Histogram for each sensor or repetition. One
dimension is the amplitude of the closed loop
cycle (i.e., the distance between peak and
valley); the other dimension is the mean of the
cycle (i.e.,[peak value + valley value]/2). The
value of each element (bin) of the histogram
can be either the actual number of closed loop
cycles that had the amplitude and average
value associated with that bin or the fraction of
the total number of cycles counted that were
associated with that bin (i.e., number of cycles
in bin divided by total number of cycles
counted).
The user enters the number of mean bins, the
number of amplitude bins, and the upper and
lower limits of the input data.
The values for the amplitude bins are
determined by difference between the upper
and lower limits on the input data and by the
number of bins. For example, if the lower limit
is 10 and the upper limit is 150, and there are 5
amplitude bins, the maximum amplitude is 150 -
100 = 50. The amplitude change between bins
and the upper limit of the smallest amplitude bin
is 50/5 = 10. Cycles with an amplitude, A, less
than 10 will be counted in the first bin. The
second bin is for 10
≤
A < 20, the third for 20
≤
A < 30, etc.
In determining the ranges for mean bins, the
actual values of the limits as well as their
difference are important. The lower limit of the
input data is also the lower limit of the first
mean bin. Assume once again that the lower
limit is 100, the upper limit 150, and that there
are 5 mean bins. In this case the first bin is for
cycles which have a mean value M, 100
≤
M <
110, the second bin 110
≤
M < 120, etc.
If C
m,a
is the count for mean range m and
amplitude range a, and M and N are the
number of mean and amplitude bins
respectively, then the output of one repetition is
arranged sequentially as (C
1,1
, C
1,2
, ... C
1,N
, C
2,1
,
C
2,2
, ... C
M,N
). Multiple repetitions are sequential
in memory. Shown in two dimensions, the
output is:
C
1,1
C
1,2
. . . C
1,N
C
2,1
C
2,2
. . . C
2,N
. . . .
. . . .
. . . .
C
M,1
C
M,2
. . . C
M,N
The histogram can have either open or closed
form. In the open form, a cycle that has an
amplitude larger than the maximum bin is
counted in the maximum bin; a cycle that has a
mean value less than the lower limit or greater
than the upper limit is counted in the minimum
or maximum mean bin. In the closed form, a
cycle that is beyond the amplitude or mean
limits is not counted.
The minimum distance between peak and
valley, parameter 8, determines the smallest
amplitude cycle that will be counted. The
distance should be less than the amplitude bin
width ([high limit - low limit]/no. amplitude bins)
or cycles with the amplitude of the first bin will
not be counted. However, if the value is too
small, processing time will be consumed
counting "cycles" which are in reality just noise.
More than one Rainflow Histogram can be
calculated using the Repetitions parameter.
The swath of input data, the size of the mean
and amplitude dimensions, the low and high
limits of the input data, and minimum distance
between peaks and valley are all selectable by
the user with parameters.
Data are output to Final Storage or to Input
Storage for further processing when the
datalogger's Output Flag is set. Partial
accumulations are kept in Intermediate Storage.
PARAM. DATA
NUMBER TYPE DESCRIPTION
01: 2 Repetitions
02: 4 Input location of input data
03: 4 Swath (per rep) of data at
input location; 1 = on line
processing
04: 4 No. of Mean bins
05: 4 No. of Amplitude Bins
06: FP Low limit of input data
07: FP High limit of input data
08: FP Minimum distance between
peak and valley