Improved OCXO's oven using active thermal insulation

This paper shows how it is possible to improve the performance of thermal enclosures by using a compensating system the principle of which has been described by F. Walls a few years ago (41st AFCS, 1987). It is shown that because of the thermal network between the outside temperature, the temperature sensor and the device to be regulated, the latter may undergo residual temperature variations which reduce the overall thermal efficiency of the oven. This paper shows how thermal transfer functions can be measured by using an experimental setup in which the node temperatures are measured by thermal sensors. By identifying the thermal response of the nodes with the theoretical transfer function under external temperature or heater excitation, the components of the equivalent R-C network can be determined. By knowing these thermal transfer functions, it is then possible to make use of a compensating system which can eliminate the parasitic static as well as dynamic thermal effects. Validating measurements and experimental results are presented which show the strong improvement achieved by this compensating system with respect to the conventional approach.<
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