| 摘要 |
Apparatus for providing a relatively constant ambient for temperature sensitive devices in which an inner oven, adapted to hold such devices, containing a heating element formed of material having a steep-sloped positive temperature coefficient of resistance (hereinafter referred to as PTC) above a threshold or anomaly temperature is placed within an outer oven containing at least one heating element formed of PTC material having a lower threshold or anomaly temperature than that of the inner oven's heating element. These heating elements also act as their own temperature regulators. The preferred embodiment employs a single toroidal PTC element located about a component mounting can. Leads connected to this heating element and the component leads are guided along the sidewalls of the electrically insulating housing of the inner oven. The entire inner oven is mounted in a heat conductive shell in which are fitted in recesses at two opposite ends toroidal PTC elements. Leads connected to the outer oven heating elements and the other leads are threaded through guide members placed in aligned apertures in the outer oven shell and are connected to terminals mounted in a base. The heating elements are locked in place by electrically insulating potting material. The heating elements are electrically connected in parallel.
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