However, when the change in the Setpoint is very small, this “start from the beginning” search routine can search over such a wide range that it will introduce a “bump” in the platform or chamber temperature that can exceed the amount of the Setpoint change. The C4 includes an intelligent PID routine that constrains the search appropriately for the change in Setpoint and thus eliminates the “PID bump”.
1.5.11Intelligent 2 Probe Control (Probe Averaging)
(Not in this release. Available in next release, without charge. Check the Sigma Systems FTP or WWW site for downloadable file.)
Intelligent 2 Probe Control allows the internal temperature of the unit under test (UUT) to be used in the temperature control algorithm. Both the primary probe, located in the chamber airstream or platform, and the secondary probe, typically located inside the UUT, are used to provide a chamber or platform response that can accelerate testing while respecting the absolute and relative limits of all the affected components.
Common single probe control strives to maintain the Setpoint temperature in the chamber airstream, or at the platform surface. If the UUT is massive, or is a poor thermal conductor, the internal temperature of the UUT can lag the chamber or platform temperature considerably. Conversely, using a second probe, buried inside the UUT, to control the temperature may achieve better UUT interior temperature control, but it will do so at the risk of extreme temperatures in the chamber or on the platform. If not carefully monitored, second probe only control can result substantial damage to the chamber or platform and UUT and risk operator injury.
Intelligent 2 Probe Control is designed to achieve the Setpoint temperature inside the UUT (probe 2) either as quickly as possible, or at a controlled ramp rate, while always respecting the limits of the controller, chamber or platform, and UUT. The user may specify the absolute limits of the exterior of the UUT as well as limit themal shock by specifying a dynamically changing “sliding scale” maximum temperature differential for the UUT skin to core temperature. Intelligent 2 Probe Control will maximize speed in achieving internal UUT Setpoint temperatures, while, at the same time, controlling the thermal stress on the UUT.
An in depth discussion of this feature can be found in Section 4.
1.5.12 Default Setup Parameters Restore
There is a procedure for erasing the current setup parameter table data and restoring it basic default values. See Section 3.3
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