Yokogawa Data Acquisition with PID Control CX2000 - Manual (Page 106)

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IM 04L31A01-01E
1.18 Computation and Report Functions (Option)
Computation Function
You can perform computations by specifying a computing equation and display the results
as computed values of a computation channel, on various displays such as the trend
display, numerical display, and bar graph display. You can use data of measurement
channels, the data of computation channels, the data of control channels, constants, etc. in
the computing equation. Computed data can be saved similar to measured data of
measurement channels. Computation is performed every scan interval.
Explanation of the computation function is also given in appendix 2, “Supplementary
Explanation of the Computation Function” and appendix 3, “Meaning and Syntax of
Computing Equations.” Read them along with this section.
Channel Numbers Dedicated to Computations
The channel numbers dedicated to computations are 31 to 60 (30 channels).
Computation Types and the Order of Precedence of Computations
The following computations can be performed. The order of precedence of computations
in descending order is functions (SQR, ABS, LOG, EXP, relational computation, logical
computation, and statistic computation), exponentiation, logical negation, multiplication/
division, addition/subtraction, greater/less relation, equal/not equal relation, logical
product, logical sum/exclusive logical sum.
Type Description
Four arithmetic operation Addition (+), subtraction, multiplication (×), and division (/)
** Power. y = X n
SQR Square root
ABS Absolute value
LOG Common logarithm
EXP Exponent. y = e x
Relational computation Determines <, ≤, >, ≥, =, or ≠ of two elements and outputs “0” or “1.”
Logical computation Determines the AND (logical product), OR (logical sum), XOR (exclusive logical
sum) of two elements, NOT (negation) of an element and outputs “0” or “1.”
Statistical computation Determines the average (AVE), maximum (MAX), minimum (MIN), sum
(TLOG) (SUM), and maximum - minimum (P-P) at specified time intervals for the
specified channels.
Rolling average Determines the moving average of the computed results of the channels to
which a computing equation has been assigned. The sampling interval and the
number of samples can be specified for each channel. The maximum sampling
interval is 1 hour; the maximum number of samples is 64.
Data That Can Be Used in Equations
Data Description
Measured data Measured value of a measurement channel or the control PV input.
Computed data Computed value of a computation channel.
Constants Set as constants K01 to K30 in the computation function.
Communication input data Values set using the communication function and written as C01 to C30
(see the DAQSTATION CX1000/CX2000 Communication Interface
User’s Manual ).
Conditions of the Remote Input signal (0 or 1) of the remote control function, written as D01 to D08.
Control Terminals
Handing of the Unit in Computations
The unit corresponding to the measured/computed data in the equation is not
compensated. In computations, measured and computed data are handled as values
without units. For example, if the measured data from channel 01 is 20 mV and the
measured data from channel 02 is 20 V, the computed result of 01 + 02 is 40.