IDEC MicroSmart Pentra - Manual (Page 90)

C ONFIGURING PID M ODULE USING W IND LDR
F C5A MicroSmart PID Module User’s Manual FC9Y-B1283 6-25
Example 2: By setting the PV correction value for the PID module to 10.0°C, the process variable (PV) of the
PID module is adjusted from 190°C to 200°C.
(3) Control Register +63: PV Filter Time Constant
The PV filter function is a software filter to stabilize the process variable (PV) affected by fluctuating processes,
such as the pressure or flow rate, by calculating first-order lag of the process variable (PV). Even if the process
variable (PV) changes as shown in the Figure 1, when the PV filter time constant is configured, the process
variable (PV) changes as shown in the Figure 2. After the PV filtering process, the process variable (PV)
reaches 63% of the process variable (PV) in T seconds.
If the PV filter time constant is too large, it adversely affects the control results due to the delay of response.
Example: If the least significant digit of the process variable (PV) is fluctuating, the fluctuation can be
suppressed by using the PV filter time constant.
Figure 1. Process variable (PV) Figure 2. Process variable (PV)
before PV filtering process after PV filtering process
(4) Control Register+59: Set Point (SP) Upper Limit/Linear Conversion Maximum Value
(5) Control Register+60: Set Point (SP) Lower Limit/Linear Conversion Minimum Value
Linear Conversion Function
The diagram below shows an example of the linear conversion. When the linear conversion maximum value is
5000 and the linear conversion minimum value is 0, the current input (4 to 20mA DC) is linearly-converted as
shown in the diagram.
Set Point (SP) Upper Limit/Linear Conversion Maximum Value
When input type is thermocouple or resistance thermometer, the linear conversion is disabled. The linear
conversion maximum value is used as the upper limit of the set point (SP). When input type is voltage/current,
configure the maximum value of input CH0 as the linear conversion maximum value. Any value within the valid
input range can be configured.
Set Point (SP) Lower Limit/Linear Conversion Minimum Value
When input type is thermocouple or resistance thermometer, the linear conversion is disabled. The linear
conversion minimum value is used as the lower limit of the set point (SP). When input type is voltage/current,
configure the minimum value of input CH0 as the linear conversion minimum value. Any value within the valid
range can be configured.
10000
5000
0
-2000
4mA 20mA
Input range
Current
Linear conversion is conducted
within this range.
Sensor
Electric Furnace
PV correction value: 10.0 °C
PID Module
Process
Variable (PV)
200°C
T
Time (Second)
Process
Variable
(PV)
Time (Second)
Process
Variable
(PV)