Chapter 10 Built-in PID Functions
10 - 14
10.5.2 Individual data area
The individual data area is in the range of K1024 ~ K2047 and a 32 word length is assigned for each of 32
loops. So, the individual data area of the nth loop is K (1024+32n) ~ K (1055+32n).
(1) _PIDn_SV (PID Set-point Value)
- Setting Area
K DEVICE AREA : K1024+32n
Unit : INT [ -32768 ~ 32767 ]
This is the SV setting part of the corresponding loop.
As described in the previous section, this is used to set the system state as desired by the user. The
system state is displayed in numeral and must be input after converted to PV according to the system gain.
In case of a system in which PV is sensed as 5000 at the temperature of 50 , if the temperature is
℃
controlled at 50 , SV is set to 5000.
℃
(2) _PIDn_T_s (PID Sampling Time)
- Setting Area
K DEVICE AREA : K1025+32n
Unit : WORD [ 0 ~ 65535 ]
This sets the sampling time of the corresponding loop.
The sampling time is a time cycle in which a control operation is performed. This can be set in the range of
0.1msec to 6553.5 msec in the unit of 0.1msec; an integer value of 1 is assigned for each 0.1ms. If 100ms
of sampling time is required, 1000 is input to _PIDn_T_s.
If the user sets the sampling time to 0, the scan cycle control mode is also set. In this case, as a control
operation occurs in each scan, a full speed control operation is performed in the current environment.
When the current scan speed is exceeeded due to the too short sampling time, The ALARM bit of
_PIDn_STATE is displayed.
(3) _PIDn_K_p (PID Propotional Gain)
- Setting Area
K DEVICE AREA : K1026+32n
Unit : REAL [ -3.4038 ~ -1.17549435e-38 , 0 , 1.17549435e-38 ~ 3.4038 ]
This sets the proportional constant for the corresponding loop. As K_p is multiplied into the P, I, D
(Proportional, Integral, Derivative) terms, the larger K_p is, the larger the proportional and derivative effects
are and the smaller the integral effect is.
If _PIDn_K_p is set to 0, P control is not performed. For more details, refer to 10.6.
K_p can be set in the short/long real number (REAL) range.
Note
_PIDn_SV
PID changes the output (MV) through several times of operations until SV equals PV. So,
when SV is 0, PIDRUN may be seen as inoperable.
If SV of a simple heater with the current temperature of 20 and PV of 2000
℃
(20 ) is set to 0,
℃
PID will output 0 as MV and will not output until PV goes below 0 (0 ).
℃
