LS Industrial Systems GLOFA G7M-DT60U(N)/DC - Page 139

Chapter 7. Usage of Various Functions
7-32
② SV(set value) / PV (present value)
SV (set value: the designated value) and PV (process value: present value) of GM7U PID operation have the
range 0 ~ 4000. The range is set with the consideration of the resolution of A/D and D/A module of GM7U
series (12 bits) and offset value. When setting the SV or PV, please be careful convert the analog value of
control object (temperature, velocity, etc.) to digital value that are the output of A/D convert module.
ⓐ When using sensor and A/D conversion module
Assume that PID control is used for temperature control with Pt100 (operation range: -200 °C ~ 600 °C), and
the goal value is 100 °C. The equivalent digital output of A/D module (current input range: 4 ~ 20mA) is 1500
if the A/D module outputs 0 (4mA) with -200 °C, and 4000(20mA) with 600 °C. Therefore, the input of SV
should be 1500, not 100.
ⓑ When using sensor and RTD module(G7F-RD2A)
Assume that PID control is used for temperature control with Pt100 (operation range: -200 °C ~ 600 °C), and
the goal value is 100 °C. The digital output of RTD module is calculated as below.
2
200010.
+
×
=
Temp
putDigitalOut
Therefore, SV should be 1500,
③ Tuning method
The GM7U perform auto-tuning operation in two methods. One is rela
y
response method and the
other is process reaction curve method.
Relayⓐ response method.
• PID parameters are obtained by On/Off operation during 1 cycle of PV variation.
• PID parameters are obtained by amplitude and period of oscillation
• The On/Off operation will be occur at the SV value.
SV
Period
Amplitude
MV