Campbell Scientific CR10X Measurement and Control System - Manual (Page 172)

SECTION 10. PROCESSING INSTRUCTIONS
10-14
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 COV/CORR
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 COV/CORR 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 COV/CORR 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 COV/CORR 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 COV/CORR 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 CR10X must perform
measurement and processing tasks in addition
to those associated with the COV/CORR
Instruction. Uninterrupted operation of the
COV/CORR 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.
*** 63 PARAMETER EXTENSION ***
Instruction 63 is used immediately following
Instructions 97 or 98 to allow the entry of a variable
number of parameters. Instruction 63 can be
entered several times in sequence if the number of
parameters requires it. There are 8 two digit
parameters. Refer to instruction being extended
(97, 98) for specifics on the use of Instruction 63.
PARAM. DATA
NUMBER TYPE DESCRIPTION
01:-08: 2 Depends upon preceding
instruction. Following
Instruction 97 RF IDs
and Phone No. 1 digit at
a time, 32 Between RF
IDs, 70 after the last RF
ID, 32 and 84 Between
RF and DC112 Phone,
and 13 To END.
Following Instruction 98
(255 character limit)
Base 10 value of ASCII
character (Appendix E)
00 TO END.
Input locations altered: 0
*** 64 PAROSCIENTIFIC "T" SERIES
PROCESSING ***
FUNCTION
Instruction 64 processes measurements made on
the Paroscientific "T" Series pressure transducer.
The transducer outputs a temperature frequency
and a pressure frequency. The frequencies are
measured using the Period Averaging Instruction,
27, which returns the period of the temperature
and pressure signals in microseconds.
Instruction 64 converts period to temperature and
pressure according to the following relationships
provided by Paroscientific.
Pressure (psi) =
C * (1 - T
0
2 /Tau 2 ) * (1 - (D * (1 - T
0
2 /Tau 2 )))
Temperature ( °C) =
Y
1
U + Y
2
U 2 + Y
3
U 3
where, C = C
1
+ C
2
U + C
3
U 2 (psi),
T
0
= T
1
+ T
2
U + T
3
U 2 + T
4
U 3 + T
5
U 4
(microsecond),
D = D
1
+ D
2
U (microsecond),
U = U(t) - U
0
(microsecond),