Nikola Tesla Books
HOT WIRE METER CONSTRUCTION 133 may be overcome by using a shunt across the meter terminals. Fig. 1 shows the meter in a plan view while Fig. 2 gives an idea of the movement. The hot wire, 1, is supported between two posts, 2, 2, to which the current is applied. Attached to the center of the hot wire by means of a fine wire hook 3, is a length of silken thread which passes in three turns around the spindle of the pivot 4, which carries the pointer. This spindle is taken from an old alarm clock. From the spindle, the silk passes to the end of a coiled spring 5, which is, in turn, held by a low post. When the wire element is heated, it lengthens and permits the silken thread to be drawn forward by the tension of the spring, turning the spindle and moving the pointer over the scale at the same time. The dimensions given in Fig. 1 are not hard and fast, but they are good in that they produce a meter of tested efficiency and value. Fig. 3 suggests the method of mounting the pivot which carries the pointer. The bridge is bent colled spring Hotwire Thread 3 turns around pivot Fig.2 Silk thread terminates in wire hook Fig. 2.-Movement of the hot wire meter
