Lake Shore 335, Руководство пользователя

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68 c
HAPTER
5: Advanced Operation
Model 335 Temperature Controller
(FIGURE 5-1). See TABLE 5-1 for a description of the Autotune stages, reasons for fail-
ure, and possible solutions. When the process completes successfully, the previous P,
I, and D parameters will be replaced by the newly acquired values. The Autotune pro-
cess can be cancelled by pressing
Autotune and choosing Yes to the “cancel Auto-
tune” prompt.
Left: Example of a screen when Autotune has been initiated. Actual screen will show the message blinking; Right: Autotune error
Autotune stages
Stage Description Purpose for stage Reason for failure Possible solution
0 Testing initial conditions Determine if Autotuning can be initiated
Curve not assigned to Input, heater not
on, or temperature not within

5 K of setpoint
Ensure curve is assigned to
input, heater is on, and

temperature is within

5 K of setpoint
1 Waiting for temperature to settle
Ensures that temperature is not still

settling toward the setpoint, or drifting
away from the setpoint
Temperature was moving too much to
properly Autotune
Allow the temperature to

settle more before initiating
Autotune
2 Testing for temperature stability
Ensures that there is no temperature
oscillation or excessive noise in the

temperature reading
May indicate that the initial P value is too
high
Use a smaller initial P value
3
Observing system response to

setpoint change
Control parameters are changed based
on observation
System response is too slow, or the
heater is too underpowered for the sys-
tem to Autotune If not already using High
range, increase initial

heater range
4
Waiting for temperature to settle
after returning setpoint to

original value
Provides a baseline for

subsequent stages
System response is too slow to Autotune,
or the new control parameters are caus-
ing instability in the control
Use a smaller initial P value
5 Testing for temperature stability
Ensures that there is no temperature
oscillation or excessive noise in the

temperature reading after control
parameter adjustment
System response is too slow to Autotune,
or the new control parameters are

causing instability in the control
Use a smaller initial P value
6
Observing system response to

setpoint change using new con-
trol parameters
Control parameters are changed again
based on observation; this is the final
stage of P-only Autotuning System response is too slow to Autotune,
or the heater is too underpowered for the
system to Autotune If not already using High
range, increase initial

heater range
7
Waiting for temperature to settle
after returning setpoint to origi-
nal value
Provides a baseline for subsequent
stages
System response is too slow to Autotune,
or the new control parameters are caus-
ing instability in the control
Use a smaller initial P value
8 Testing for temperature stability
Ensures that there is no temperature
oscillation or excessive noise in the tem-
perature reading after control parameter
adjustment
System response is too slow to Autotune,
or the new control parameters are caus-
ing instability in the control
Use a smaller initial P value
9
First of two stages of observing

system response to setpoint
change using new control

parameters
Compiles data for characterizing

the system
Will not fail in this stage Not applicable
10
Second of two stages of observing
system response to setpoint
change using new

control parameters
Control parameters are changed again
based on observation; this is the final
stage of PI and PID Autotuning System response is too slow, or the
heater is too underpowered for the sys-
tem to Autotune If not already using High
range, increase initial

heater range
Menu Navigation:
Autotune
Q
Input ( A, B )
Q
(Autotune P, Autotune PI, Autotune PID)
Interface Command:
ATUNE
FIGURE 5-1
TABLE 5-1