Operator`s manual

SECTION 10. PROCESSING INSTRUCTIONS
10-14
N' is the number of input scans in the last
averaging period
NT is the total number of input samples
processed in the Output Interval
INTERMEDIATE STORAGE REQUIREMENTS
The number of Intermediate locations will
depend upon the number of input values and
outputs desired:
1. Define K as the number of input values.
2. Define S as the maximum of either the
variances, standard deviations, or C, where
C = K if K < the number of correlations
requested, or
C = number of correlations + 1 if K > the
number of correlations requested.
3. Define Q as the maximum of either the
covariances or correlations desired.
4. Define P as the total number of outputs
desired.
The amount of intermediate memory locations
(IML) required, is then given by:
IML = K + S + Q + P + 2
EXECUTION TIME
If K, S, and Q are defined as in the previous
section, the execution time of the CV/CR
Instruction in milliseconds can be approximated
by:
T(ms) = 1.1K + 0.5S + 0.9Q + 1.8
When evaluating how frequently input samples
can be processed by the CV/CR Instruction (i.e.,
determining the minimum program table
execution interval), the time required to make
the measurements and order the input values
must be added to the CV/CR execution time.
Two alternatives exist for the measurement
portion of the programming. The fastest method
is to group as many sensors as possible into the
fewest measurement instructions, ignoring the
Input location order required by the CV/CR
Instruction. After the measurements are made,
use "move" instructions (i.e., 31 and 54) to
obtain the proper input order. The slower
alternative is to order separate measurement
instructions directly as required by the CV/CR
Instruction. While avoiding "move" instructions,
this approach uses more measurement
instructions. The reason the first method is in
general faster is that less overhead time is
required in going from one measurement to
another within a single instruction (using the
"repetitions" feature) than in going from one
measurement instruction to another.
In many situations, the 21X must perform
measurement and processing tasks in addition
to those associated with the CV/CR Instruction.
Uninterrupted operation of the CV/CR
Instruction is assured by entering it in Program
Table 1 (highest priority) and placing the
additional tasks in Program Table 2.
A covariance correlation example is given in
Section 8.
*** 66 ARCTAN ***
FUNCTION
Calculate the angle in degrees whose tangent is
X/Y. The polarity of X and Y must be known to
determine the quadrant of the angle, as shown
here. If 0 is entered for Parameter 2, the
Arctangent of X is the result (limits of the
function are -90
o
< ARCTAN < 90
o
).
Quadrant Sign of X Sign of Y
I++
II + -
III -
IV +
PAR. DATA
NO. TYPE DESCRIPTION
01: 4 Input location of X [X]
02: 4 Input location of Y [Y]
03: 4 Destination input location for
ARCTAN(X/Y)
Input locations altered: 1