4. INTELLIGENT 2 PROBE CONTROL
(Probe Averaging)
(Not in this release. Available in next release, without charge. Contact Sigma Systems to receive a revised firmware EEPROM.)
Intelligent 2 Probe Control allows the internal temperature of the UUT (Unit Under Test) to be used in the temperature control algorithm. Both the primary probe, located in the chamber airstream or in the 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 either 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. If, as a result of measuring the chamber air stream or platform temperature only, the test is terminated too quickly, the UUT may not have actually achieved the desired setpoint test temperature. 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 and thus at the UUT surface as well.
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 UUT as well as limit thermal shock by specifying a proportionally applied 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.
Note: For the balance of this section, the description of Intelligent 2 Probe Control will be related to operation of temperature chamber. All of this information applies to thermal platforms as well, but they are not mentioned further to make the text easier to read.
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