A modified form of high temperature thermostat

Abstract

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The apparatus is for the purpose of maintaining an electric furnace at a constant temperature for considerable periods of time (weeks or months) in spite of fluctuations in the supply voltage. Several auxiliary furnaces may be maintained at various temperatures by means of the apparatus, but the temperature control is not so accurate as in the case of the thermostat furnace itself. Should the supply current fail or the temperature control be temporarily lost owing to the failure of a relay, the apparatus is not damaged in any way by the violent displacement of the mercury, and the furnaces will return to their original temperatures as soon as the defect is remedied. By the correct proportioning of the apparatus the effect of room temperature changes on the temperature of the controlled furnaces may be pratically eliminated. The usual low temperature air bulb maintained in ice is replaced by the barometer column which requires no attention.