31
apply PV startup first, if PV startup function works, PV preparation function will not be activated.
Curve fitting
Curve fitting is adopted as a kind of control technology for AI-516P series instrument. As controlled
process often has lag time in system response, by the way of curve fitting the instrument will
smooth the turning point of the linear heating-up, cooling-down and constant temperature curves
automatically. The degree of the smooth is relevant with the system
’
s lag time t (t=d+CtI) ; the
longer of the lag time, the curve will more smooth. On the opposite the smooth
function will be weaker. Generally the shorter of the process lag time (such as temperature inertia),
the better of the program control on effect. By the way of the curve fitting to deal with the program
curves, will avoid overshoot.
Note: The characteristic of the curve fitting will force the program control to generate fixed negative
deviation during the linear heating-up and fixed positive deviation during the linear cooling-down,
the deviation is direct proportional to the lag time and the speed of heating-up (cooling-down). This
phenomenon is normal.
5. Programming and operation (For AI-516P only)
5.1 Ramp Mode(PAF : B=0)
Programming of instrument has uniform format of temperature-time-temperature, which means
temperature
“
A
”
(SP 1),passed Time
“
A
”
(t01), then reached Temperature
“
B
”
(SP 2). The unit
of temperature set is
℃
and the unit of time set is minute. The following example includes 5 steps,
which is linear temperature heating up, constant temperature, linear temperature cooling down,
jump cycling, ready, Hold..
StEP1: SP 1=100 , t 1=30.0
Start linear temperature heating up from 100
℃
, and the time needed
30 minutes to reach
SP 2(400 degree).
StEP2: SP 2=400 , t 2=60.0
Temperature raised to 400
℃
, slope of raising curve is 10
℃
/minute,
The program take 60
minutes to raise temperature to SP3 (400 degree). It means keep the same temperature in 60
minutes.
StEP3: SP 3=400 , t 3=120.0
This is the step for temperature cooling down, slope of cooling curve
is 2
℃
/minute, and
the time needed is 120 minutes to reach SP4 (160degree).
StEP4: SP 4=160 , t 4=0.0
When temperature reached 160 degree, the program get in Hold state.
If need go to next step, it needed operator to executed the
“
run
”
for next step.
StEP5: SP 5=160 , t05=-1.0
Jump to StEP1 to start from beginning.
In this example, it is assumed that the deviation high alarm is set to 5
℃
. Because the temperature
of StEP 5 is 160
℃
, and the temperature of StEP1 is 100
℃
, when program jumps from StEP 5 to
StEP 1, the program will change to preparation state at first(if preparation mode
“
rdy
”
was
enabled), i.e., Control the temperature until the deviation between setpoint and PV is less than
deviation high alarm value. After temperature is controlled to 105
℃
, the program will be started
from StEP 1, and run the above steps again. The temperature control drawing was shown below.
