Yokogawa Data Acquisition with PID Control CX2000 User Manual
Page 30
1-18
IM 04L31A01-01E
• Loop control with PV switching
Single-loop control that switches between two PV inputs (PV1 and PV2) according to
the following conditions.
PID
SP
PV1 PV2
OUT
Input Switching Condition ([Method] on the setting display)
• Auto switching according to the PV range ([Range] on the setting display)
Switches PV inputs (PV1 and PV2) automatically according to the preset “PV
switching low-limit” and “PV switching high-limit” as shown in the following figure.
However, PV1 must be less than PV2.
PV
PV2
PV1
PV switching low limit
PV switching high limit
Process value according
to the equation
PV range high limit
PV range low limit
The PV value is computed using the following equation when “PV switching lower limit
< PV1 ≤ PV switching upper limit” and “PV switching lower limit ≤ PV2 < PV switching
upper limit.”
Process value = 1–
× PV input 1+
× PV input 2
PV input 1 – PV switching low limit
PV switching high limit – PV switching low limit
PV input 1 – PV switching low limit
PV switching high limit – PV switching low limit
• Auto switching according to the PV switching upper limit ([PVHigh] on the setting display)
The preset “PV switching upper limit” and PV1 are compared. Auto switching is
performed according to the following conditions. The switching hysteresis is
approximately 0.5% of the PV range span.
When PV1 ≤ PV switching upper value: Switch to PV1
When PV1 > PV switching upper value: Switch to PV2
• Switching through control input ([Signal] on the setting display)
Input is switched using “PV switching (loops 1 to 4)” (see page 1-27) as follows:
Contact input is OFF: Switch to PV1. Contact input is ON: Switch to PV2.
Analog Retransmission
Outputs the specified computed result instead of the computed PID value from the
control output terminal. In control setting mode, you can set the equation, output span,
unit, and method of processing computation errors for the loop specified for analog
retransmission. Unlike the 3 control modes above, control functions such as upper/lower
output value and preset output are not supported.
Difference in the Control Input Configuration According to the 6/4 Loop Selection
and Control Mode (when PV/SP computation is OFF)
The input signal assignments of each terminal of the analog control input block vary
depending on the 6/4 loop selection and the selected control mode as shown in the
figure below. If set to 6 loops, the control mode of the 5
th
and 6
th
loops can only be set to
single-loop control.
LOOP1
2
1
PV
(RSP)
(RSP)
PV
PV1
PV2
LOOP2
LOOP5
LOOP6
2
1
PV
1
PV
1
PV
(RSP)
PV
PV1
PV2
LOOP3
2
1
PV
(RSP)
(RSP)
PV
PV1
PV2
LOOP4
2
1
PV
(RSP)
PV
PV1
PV2
• 6 loops
PV, PV1, PV2: PV input, (RSP): RSP input
(not used during program control), : unused terminal
During single-loop control
During cascade control
During loop control with
PV switching
[Control mode setting]
1.3 Basic Settings of Control