Yokogawa Data Acquisition with PID Control CX2000 - Manual (Page 20)

1-8
IM 04L31A01-01E
Analog Retransmission (Style Number S3 or Later)
Output comes from the control output channels per the results of the specified equation.
The computed result is converted to a percentage of the output span (ranging from 0.0%
for the lower limit of the output span to 100.0% for the upper limit), and then outputs
according to the output format below. The output interval is the same as the control
output interval.
• Time proportional relay contact output: Outputs an ON/OFF signal having a pulse
width proportional to the time as relay contact
point signal according to the computed
values.
• Time proportional pulse output: Output an ON/OFF signal having a pulse
width proportional to the time as voltage
according to the computed values.
• Current output: Continuously output a current (analog signal)
proportional to the computed PID values.
Note
• The output value while initialization occurs after turning the power ON or OFF is 0 mA or 0
V.
• The output value while in setup mode or when closing setup mode and switching to
operation mode is 0 mA or 0 V.
• Analog retransmission is handled the same as when control mode is OFF. Control
functions such as upper/lower limit of output value and preset output are not supported.
The following is a block diagram of analog retransmission:
Measurement input/
computation input
Output
Analog retransmission computation section Manual operation
Output data created
Automatic (AUT)
Manual (MAN)
OUT
Control input
Remote input/control module relay
Internal switches Communication data
PV/SP/control output
The order of processing for PID computation and analog retransmission is as follows:
Start control task
PID
computation
Analog retransmission
computation
Display/recording/
terminal output
Stop control task
Input value, data used
in computation
(newest value)
Previous PV, previous
SP, previous output
value (PID computation)
Previous output value
(analog retransmission
output)
PV, SP output value
(PID computation)
Output value (analog
retransmission output)
Processing of all
control loops
Processing of all
analog retransmission
loops
Processing of all loops
1.2 Control Function Overview