## Around a glass cylinder

Phase Splitting Circuits

In order to facilitate observation or to simplify the pattern, it is frequently desirable to separate the front and rear patterns. In other words, patterns, such as we have shown, can be said to have front and rear portions, which are on the same horizontal plane. That is why, under certain phase conditions, certain peaks or loops are covered by

Fig. 120. This circuit is used for separating the front and rear portions of a pattern, making the interpretation of high ratio figures much simpler. For a circular pattern the reactance of C should equal resistance of R at the base frequency.

other loops. When the frequency ratio is greater than 10 to 1, comprehension of these patterns is not easy. To simplify them, or at least to make interpretation easier, the pattern can be displaced on a circle or an ellipse.

The circuit used is shown in figure 120. It is substantially the same as that used in figure 94 for securing conventional patterns, except for the addition of a phase splitting system, whereby the front and rear portions of the pattern are separated. The 10-1 pattern of figure 117 now looks like the pattern shown in figure 121. A 13-2 pattern spread out as an ellipse is shown in figure 122. A 19-2 pattern, with the front and rear traces spread, is shown in figure 123. Frankly, we

Fig. 121. pattern.

A 10-1 ratio Compare Fig. 117.

Fig. 121. pattern.

A 10-1 ratio Compare Fig. 117.

123. A 19-2 ratio pattern.

do not feel that there is any real need for such Lissajous figures during routine frequency calibration. With careful operation with ratios up to 10-1, complete coverage can be had with a high degree of accuracy. However, we show the schematic diagram and several examples for those who may want to develop such patterns. To establish the fre-

quency ratio of single line patterns, count the number of loops and the ratio is the number of loops to 1.

In patterns which indicate fractional ratios, count the number of loops and the number of lines of intersections made by the loops. In figures 122 and 123, there is one such line of intersections. The frequency ratio is equal to the number of loops or peaks on the circumference divided by the term (one plus the number of lines of intersections). Thus figure 122 shows a ratio of 13—2 and figure 123 shows a frequency ratio of 19 to 2.

Another form of pattern, due to N. V. Kipping, is the gear-shaped figure on a circular axis. This produces a pattern such as that shown in figure 124. The circuit is shown in figure 125. One voltage is applied across both sets of plates in quadrature, by means of the phase splitting circuit. As a result of this circuit, the beam spot traces a

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