5300 Series TECSource User’s Manual · Page 31
value until the set point is achieved without oscillation. In many systems, the D
term is not needed and may be left at zero.
For additional information on PID loop tuning, consult online resources such as
Wikipedia (http://en.wikipedia.org/wiki/PID_controller) or search for terms such
as “Ziegler-Nichols method”, or “PID Loop”.
Using the AutoTune Function
The TECSource is capable of automatically determining PID parameters for
most applications. Using a form of the Ziegler-Nichols method, the TECSource
will step through a process to determine the thermal response of the mount,
which can then be used in a mathematical model to calculate the PID
parameters.
The PID parameters generated by AutoTune are not necessarily the ideal PID
parameters, and small improvements may be possible by further refining the
results manually.
Before starting the AutoTune function, it is best to begin from ambient
conditions, either with the TEC off and the mount stabilized at ambient, or the
TEC on and the set point around 25°C. While this is not required, it can produce
better results. AutoTune only functions in temperature mode. PID parameters
must be manually determined for R mode.
Make sure the current and temperature limits are set prior to starting AutoTune.
AutoTune will intentionally cause your mount to oscillate, so the temperature
limit should be at least 5 to 10 degrees away from the test point to avoid tripping
a limit during the process.
To start the AutoTune function, select the AutoTune PID menu entry from the
main menu and press ENTER. If you wish to perform AutoTune remotely, see the
following section for more information.
The instrument will ask for the AutoTune test point. You will want to select your
typical operating point. If you will be operating at two or more set points, you will
usually want to select the set point furthest away from ambient. Once the
temperature test point is selected, press ENTER.
The instrument asks for a final confirmation to start the AutoTune process. Press
ENTER to start, or MENU to exit.
Once the AutoTune process starts, the display will indicate the present
temperature, which step it is performing, and the word “AutoTune” will flash on
the display.
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