. Dental electro-therapeutics. Fig. 00.—Pelton electric furnace. Platinum, although capable of resisting great heat, willoccasionally become overheated and the fusing of the coildestroy the furnace; the principal cause of this is switchingon current too suddenly. The wire is wound in grooveson the outer surface of the muffle which provide perfectinsulation when expansion takes place during heating; a shortcircuit would cause fusing of the wire. The wire used in wiring a muffle varies in diameter andlength according to the voltage of the current to be used and ELECTRICAL FURNACES 135. £ 13G DEN
. Dental electro-therapeutics. Fig. 00.—Pelton electric furnace. Platinum, although capable of resisting great heat, willoccasionally become overheated and the fusing of the coildestroy the furnace; the principal cause of this is switchingon current too suddenly. The wire is wound in grooveson the outer surface of the muffle which provide perfectinsulation when expansion takes place during heating; a shortcircuit would cause fusing of the wire. The wire used in wiring a muffle varies in diameter andlength according to the voltage of the current to be used and ELECTRICAL FURNACES 135. £ 13G DENTAL ELECTRICAL APPLIANCES the temperature required. Very accurate calculations arenecessary to determine these points and to ensure correctresistance in heating the wire to the right temperature with-out overheating, or, on the other hand, not heat the furnacesufficiently. Pyrometer.—The pyrometer is used for registering thetemperature generated in a furnace. It is connected by athermo-couple to the muffle. The fusing-point of the metalor porcelain body being known, the required heat is registeredon the dial of the pyrometer and fusing accomplished withoutopening the furnace. The pyrometer is a very delicate instrument and some-what expensive. It works independently of the ordinaryelectric current supply and develops a thermal-electriccurrent in its own circuit. The thermo-couple consistsof two pieces of wire, platinum, and iridium, which areinsulated from each other, except at their extreme of the ends are fused together while the other two haveflexible wires att
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Keywords: ., bookauthor, bookcentury1900, bookdecade1910, booksubjectdentistry
