The Indicator Box with Coil, Needle and Scale, as It is Used in Connection with the Anemometer (Fig. 1)
The core for the coil is cut from a piece of 1/4-in. iron rod, 1-1/4 in. long, and a slot is cut in each end, 1/4 in. deep, into which brass strips are inserted and soldered, or otherwise fastened. The strips of brass are 3/16 in. wide, one 1-1/2 in. long and the other 3/4 in. Two 1/16 in. holes are drilled in the end of the long piece, and one 1/16 in. hole in the end of the short piece. The complete core with the brass ends is shown in Fig. 2.
The Metal Core for the Coil... (Fig. 2)
...and the Bearing Block for the Axis of the Needle (Fig. 3)
The needle B, Fig. 1, is made of a copper or brass wire, about 6 in. long, and is mounted on an axis at C. The detail of the bearing for the axis is shown in Fig. 3. The axis D is a piece of wood fitted in the U-shaped piece of brass and made to turn on brads as bearings, the center being pierced to receive the end of the needle. After locating the bearing for the axis C, Fig. 1, it is fastened in place so that the upper end or pointer of the needle will travel over the scale. The needle is then attached to the bearing after having been passed through the inner hole of the longer brass strip of the core, and the coil is fitted with the core in the manner shown at D. A light brass coil spring is attached to each end of the core, as shown at E and F, the latter being held with a string, G, whose end is tied to a brad on the outside of the box, for adjustment. A better device could be substituted by attaching the end of the spring F to a nut and using a knurled-head bolt passed through the box side. One of the wires from the coil is attached to a push button, H, to be used when a reading of the instrument is made. The connections for the instrument consist of one binding post and a push button.
The Anemometer as It is Mounted on a Standard Similar to a Small Windmill Weather Vane (Fig. 4)