AUBER INSTRUMENTS
WWW.AUBERINS.COM
2021.01
P4/6
and used for the system. Please note that auto-tuning is only for PID control
mode. There is no need for auto-tune when using ON/OFF mode (when P = 0).
To stop the auto-tuning, enter the parameter setting mode, set At = OFF. Then,
the previous PID parameters values are resumed.
AT start
AT calculation
AT end
ON
OFF
ON
OFF
ON/OFF
PID
Figure 5. Auto tuning
SV
PV
Hy2
1
.
0
Figure 4. System setup flow chart.
SET 3S
SET
SET
SET
SET
SET
SET
SET
SET
SET
SET
SET
SET
SET
AL1
999
.
9
ALP 1
Alarm 1 Definition
ALP 2
Alarm 2 Definition
Cool
Cooling Control
OUTH
Output High Limit
Lock
Configuration Privilege
Sn
Input Type
OPA
Output Mode
CF
Display Unit
DIH
Input High Limit
DIL
Input Low Limit
SC
0
.
0
P
15
.
0
I
240
D
30
AT
OFF
t
10
Hy1
1
.
0
DP
1
ALP2
0
COOL
OFF
Hy
1
.
0
AL2
0
SET
SET
SET
outh
100
LOCK
0
ALP1
0
85
.
5
10
AL1
Alarm1 Setting
AL2
Alarm2 Setting
SC
Input Offset
P
Proportional Constant
I
Integral Time
D
Derivative Time
At
Auto Tune
T
Cycle Time
Hy
Hysteresis Band
Hy 1
Alarm 1 Hysteresis Band
Hy 2
Alarm 2 Hysteresis Band
dP
Decimal Point Position
Sn
k
OPA
0
Dil
0
dih
999
.
9
cf
c
Time
SET
SET
SET
SET
SET
PV
4.3 Control action explanations
4.3.1 PID
The values of the P, I, and D parameters are critical for good response time,
accuracy and stability of the system. Using the Auto-Tune function to
automatically determine these parameters is recommended for the first time
user. If the auto tuning result is not satisfactory, you can manually fine-tune the
PID constants for improved performance.
Proportional Constant (P):
P is also called the proportional band. Its unit is
the degree of temperature. For example, P = 50 means the proportional band
is 50 degrees. Assuming the set temperature SV = 200. When integral, I, and
derivative, d, actions are removed - the controller output power will change
from 100% to 0% when temperature increases from 150 to 200 ° C. The
smaller the P value is, the stronger action will be for the same temperature
difference between SV and PV.
Please note: for on/off control mode, P is
set to 0.
Integral time (I):
Brings the system up to the set value by adding to the output
that is proportional to how far the process value (PV) is from the set value (SV)
and how long it has been there. When I decreases, the response speed is
faster but the system is less stable. When I increases, the response speed is
slower, but the system is more stable. When I = 0, the integration is turned off.
It becomes to a PD controller that is useful for very slow system.
Derivative time (d):
Responds to the rate of PV change, so that the controller
can compensate in advance before |SV-PV| gets too big. A larger number
increases its action. Setting d-value too small or too large would decrease
system stability, causing oscillation or even non-convergence. Normally, d is
set to ¼ of the I value. However, when the controller is in on/off mode (P = 0)
and cooling control is turned on, d means Delay Timer of the Anti-Short Cycle
Delay (Asd) function. The delay time ranges from 1-200 minutes. (See 4.3.3
for details).
4.3.2 On/off control mode
It is necessary for inductive loads such as motors, compressors, or solenoid
valves that do not like to take pulsed power. It works like a mechanical
thermostat. When the temperature passes the SV+Hy, the heater will turn off.
When the temperature drops back to SV-Hy, the heater will turn on again. (In
cooling mode, the cooler turns on when temperature passes SV+Hy, and turns
off when temperature drops back to SV-Hy).
To use the on/off mode, set P =
0 and Hy to the desired band.
Then I and D parameters are not used when
controller is in heating mode. It can be left at any value. In the cooling mode,
the D value is used for Anti-Short Delay time. Its value is in minutes (See 4.3.3
for details).
4.3.3 Cooling control
When controller is used for cooling control and load is a compressor, it should
not turn on the compressor when its refrigerant is at high pressure (just after
turned off). Otherwise, the compressor can be damaged in short time. Two
methods are commonly used to prevent the rapid cycling of the compressor.
One is to use on/off control mode (instead of the PID control mode) with wide
enough hysteresis band, and long cycle rate. The other is to use the Anti-Short
Cycle Delay (ASd) function. ASd establishes the minimum time that the N.O.
contacts remain open (after reaching cutout) before closing again. The delay
overrides any Load Demand and does not allow the N.O. contacts to close until
the set time-delay value has elapsed. ASd gives time to release the refrigerant
pressure through evaporator. This controller allows the user to use both
methods to protect the compressor. You should set the P = 0 for on/off mode.
Hy should not be less than 2 degrees unless you really need a tight control. The
cycle rate should be set for 20 second or longer. The D is typically set to 4- 6
(minutes).
4.3.4 Manual mode
Manual mode allows the user to control the output as a percentage of the total
heater power. It is like a dial on a stove. The output is independent of the
temperature sensor reading. One application example is controlling the strength
of boiling during beer brewing. You can use the manual mode to control the
boiling so that it will not boil over to make a mess. The manual mode can be
switched from PID mode but not from on/off mode. This controller offers a
“
bumpless
”
switch from the PID to manual mode. If the controller outputs 75%
of power at PID mode, the controller will stay at 75% when it is switched to the
manual mode, until it is adjusted manually. See Figure 3 for how to switch the
display mode.
To activate the manual control
, pressing the
◄
key for 3
seconds or until the bottom display shows H at the most left digit. The H
indicating the controller is in manual mode. The number at the right is the
percentage of output. Press the
▼
or
▲
key to adjust the power. To switch back
to PID mode, pressing the
◄
key for 3 seconds or until the H disappeared.
