Abstract
THE Zenith Electric Co., Ltd., Villiers Road, London, N.W.2, has issued a catalogue describing its wire-wound vitreous embedded resistors (resistances). They consist of a ceramic tube or rod spirally wound with resistance wire and embedded in vitreous enamel. This company was the first to produce resistors of this type in Great Britain. Modern requirements have created a need for resistors of comparatively small size characterized by their resistance remaining steady under all working conditions. The requirements of high ohmic value necessitate resistance wires of the smallest possible gauges; they are naturally delicate and fragile, and trustworthiness makes it necessary that the wires be embedded in, and protected by, a covering absolutely impervious to the entry of moisture or to the attacks of acids, alkalis or other deleterious substances. It must be capable also of withstanding high overloads and repeated heating and cooling, without developing flaws, crazing or cracks which would permit the entry of moisture, and quickly lead to open circuit, by the corrosion of the fine-gauge wires employed. The foregoing requirements seem to be fully met in practice by the ‘ceramite’ embedding process, which is much superior to ordinary vitreous enamels. Being akin to porcelain, it has very high insulating properties, possesses great mechanical strength and resists chemical attack. The new ‘ceramite’ resistor complies with all the latest Government specifications for tropical grade resistors.
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High Resistance Resistors. Nature 144, 148 (1939). https://doi.org/10.1038/144148c0
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DOI: https://doi.org/10.1038/144148c0