Cryo-con Model 24C Basic Setup and Operation
System Characterization.
System characterization is the process of using autotune to generate optimal PID
coefficients for each setpoint over a wide range of possible setpoints.
The characterization process is performed once. Then, the setpoints and
corresponding generated PID values are transferred to an internal PID table.
Thereafter, the system is efficiently controlled using the Table control mode.
Autotune Setup and Execution
The Autotune menu for either control loop is accessed by pressing the Auto Tune key
from the Home Operate Screen.
Upon entry, the autotune state variable is set to Idle and the P, I and D fields on the
bottom of the display will be blank.
As described above, various setup conditions must be met before autotune can be
performed:
1. The Model 24C must be in Control mode.
2. Both the output power and the process temperature must be stable. The user
must stabilize the process before the autotune function can accurately model
it. If the process is not stable, erroneous values of P, I and D will be
generated.
3. The input control channel units must be in temperature, not sensor units of
Volts or Ohms. This is because PID control is a linear process and sensor
output is generally non-linear. Note that the Model 24C can be manually
tuned using sensor units but autotuning cannot be performed.
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