Yokogawa Data Acquisition with PID Control CX2000 - Manual (Page 33)

1-21
IM 04L31A01-01E
Explanation of Functions
3
2
1
4
5
6
7
8
9
10
11
12
13
14
Control Output
Select the type of control output from the following. The type can be selected for each loop.
• Time proportional PID relay contact output
• Time proportional PID voltage pulse output
• Current output (continuous PID control output)
• On/off control relay contact output
Time Proportional PID
The result of PID computation is output using a pulse width of an ON/OFF signal that is
proportional to the time. The pulse width is calculated using the following equation with
the cycle time (control output period, see next section) taken to be 100%.
Pulse width = Control output (%) × cycle time
You can select relay output or voltage pulse for the output type.
Current Output (Continuous PID Control Output)
The result of PID computation is output using a current (analog signal) that is
proportional to the computed PID value. There are four types of output current.
On/Off Control Relay Contact Output
The on and off signals are output using a relay according to the polarity of the deviation
between the SP and PV.
Cycle Time
Set the cycle time (control output cycle) for the time proportional PID in the range of 1 s
to 1000 s. Setting a short cycle time enables precise control. However, the life of the
output relay and the input contact on the control element may be shortened, because the
number of ON/OFF operations increases. In general, the cycle time is set around 10 s to
30 s for relay output. You can select the cycle time for each loop.
Ratio of the
ON time
0.0 50.0
Output display value
Cycle time
OFF
ON
When the cycle time
is short
OFF
ON
When the cycle time is of
medium length
OFF
ON
When the cycle time is long
OFF
ON
100.0
Selecting the Analog Output
Select the type of output current when current output is used from the following:
4-20 mA, 0-20 mA, 20-4 mA, and 20-0 mA.
1.3 Basic Settings of Control