L'niversitv, New Haven, Conn. T HE "transient visualizer" which is described in by different elements of the oscillograph or (2) they are this paper was developed to make possible a more to be taken at different times on the same film. Several satisfactory study of transients by means of the different circuits may be connected so that their reoscillograph. It is, of course, well known that the spective phenomena may be studied (or recorded) in oscillograph has been an effective instrument for many succession. years for studying a-c. phenomena where the successive The main part of the visualizer drum consists of six cycles are identical and are repeated synchronously, circular sections mounted on a common shaft, as shown but in the case of transient phenomena which are not in Fig. 1. This shaft is driven through gears by a selfrecurrent, there have been limitations to its usefulness. starting synchronous motor. The circumference of It has not been possible to make visual observations five of the drum sections is divided into two segments, of transients, because the trace produced by a single one a conductor and the other an insulator. The consweep of the light spot across the viewing screen is ducting segments are of various lengths, for use with insufficient to make an impression on the eye. As a transients of different duration, and their relative consequence, only photographic records were obtainable angular spacing around the circumference of the drum and satisfactory results were difficult to obtain for two is such as to give maximum flexibility in its use. The reasons. In the first place, the amplitude of the curves sixth section is one continuous conductor and is eleccould not be determined beforehand, and in the second trically connected to the five others.place it was difficult to place the curves properly on the Brushes mounted on a common arm make contact film.
The purpose of this paper is to describe a wattmeter, for measuring power of a few microwatts or more, a phase shifting bridge for controlling the angular relation of two potentials without changing their amplitudes, and a voltmeter for measuring potentials of a few millivolts without amplifying.
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