Nikola Tesla Books
Books written by or about Nikola Tesla
Colorado Springs
Dec. 2, 1899
Various ways of tuning circuits or determining the maximum of resonant rise.
In the course of the experiments conducted here a number of such ways have been resorted to most of which have been described or at least referred to, but it may be useful to record here once more those which have been found most satisfactory. They are diagrammatically illustrated in Figs. 1 - 5. below:
In arrangement illustrated in Fig. 1. a small circuit c1, in very loose inductive connection with the resonating circuit C, is used to detect the maximum. This small circuit c1 which exercises no appreciable reaction upon circuit C contains another coil c'' or else a resistance which is noninductive for the purpose of adjusting the effect to suit the indicating device d which is most generally a microscopic spark gap, vacuum tube or any hot wire instrument, as a minute lamp specially made to suit the purpose, a Cardew voltmeter or any other instrument. In Fig. 2. the adjustment of the effect upon d is effected by turning the circuit around a point o or else by approaching small circuit c1 to or receding with same from circuit C. In Fig. 3. a number of turns of the resonating circuit C are spanned by device d, this number being adjustable. In Fig. 4. again a small coil c'' in series with coil C is placed inductively in connection with a small circuit c''' which again may be adjustable in the manner shown or in any other way. Finally in Fig. 5. a small coil c'' in series with C is spanned by device d. Coil c'' has its turns adjustable. This method seems best.
308
December 2
Tesla provides a review of the methods for the purpose of experimental determination of the resonant state in the coil C (please see Fig. 1-5). The measurement circuit with the maximum coil excitation indicator indicated he connects three ways: In the auxiliary circuit with the weak inductive coupling (Fig. 1 and 2); to the portion of the coil (Fig. 3); and in series with the coil (Fig. 4 and 5). Here for the first time in these notes he also mentions the series of possible indicator types as for instance microscopic spark, vacuum tube (the indication is by gas luminescence); any instrument with a heating filament (e.g., a bulb). Cardew voltmeter*. He showed several ways to adjust the resonance indication sensitivity as well as by mutual link regulation (Fig. 1 and 2), by resistor in indicator circuit (Fig. 4) and by means of an autotransformer link (Fig. 3 and 5).
* Thermal instrument of maximum current 0.33A, considered very successful in Tesla's time.
