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C4 Manual Rev 7.5.2
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.