Yokogawa DR240 - Manual (Page 223)

12-3 IM DR232-01E
Executing Computation (Available with the /M1 Model)
12
12.1 Overview of the Computation Function
Handling of data for computation
For computation, measured/computed data is treated as a value having no unit. For instance, if
the measured data for channel 001 is 20 mV and the measured data for channel 002 is 20 V, the
computation result of “001 + 002” will be 40.
Priority of Operators
Priority of operators when they are used in an equation is shown below. Operators are listed in
order of priority, from the highest to the lowest.
Type Operator
Function ABS(), SQR(), LOG(), LN(), EXP(), MAX(), MIN(), P-P(), SUM(),
AVE(), PRE(), HOLD():, RESET():
Repeated multiplication **
Sign, logical negation +, -, NOT
Multiplication, division *, /
Addition, subtraction +, -
Greater, smaller .GT., .LT., .GE., .LE.
Equal, not equal .EQ., .NE.
Logical AND AND
Logical OR, exclusive OR OR, XOR
Alarm
Up to 4 alarms can be set for each computation channel. Only two types of alarm are available:
upper-limit alarm (H) and lower-limit alarm (L). Hysteresis is always set to “0”. For a detailed
description of alarm setting, refer to 8.1, “Setting Alarms and Relays (including internal
switches)” (page 8-1).
Event/action function
The event/action function can be used to start/stop computation and clear computation channels in
case an event takes place. refer to 9.1, “Setting Event/Action Functions” (page 9-1).
Actions to be taken in case of overflow and computation error
Actions to be taken in case of an error during computation can be specified.
• Error display: +OVER or -OVER is displayed.
• Error data during TLOG or CLOG: The operator is asked to select whether to display the data
as a computation error or ignore the error and continue computation.
• Overflow data during TLOG or CLOG: The operator is asked to select whether to display the
data as a computation error or ignore the error and continue computation. The operator is also
asked to select whether or not the data be used as the upper-/lower-limit value.
Description of the upper-/lower-limit value is given below:
Measurement channels to which linear scaling is applied: Specified scaling upper-/lower-
limit
Measurement channels to which no linear scaling is applied: Upper-/lower-limit of the
measuring range
Computation channels: Specified LEFT/RIGHT value