The Operation Of Oscilloscopes

Author: J.B. Hoag

An oscilloscope is an instrument which contains a cathode-ray tube with its power supplies, with amplifiers for the deflection plates and with special circuits which permit the electron beam to be deflected over the screen surface in prearranged patterns. There are a great many uses to which the oscilloscope can be put, among which we may mention: studies of the wave form of various voltages and currents; instantaneous plotting of curves such as those of tubes or of the hysteresis phenomena in magnetism; the measurement of phase and time delays; the measurement of frequency; checking of the alignment of radio amplifiers; measurement of the percentage modulation of transmitting tubes; as the picture forming element of a television receiving set, etc. Most of the applications fall into the following simple classifications :

1. The study of change of voltage or current with time.

2. Comparison of two voltages or currents with respect to their relative amplitudes.

3. Comparison of the relative phase of one current with another, of one voltage with another, or of a current with a voltage.

As examples of the first class of problems we may cite: measurements of the time of delay of pulses returning from reflecting bodies such as the ionosphere, studies of fading, of field strength, and the waveform of atmospherics. As examples of the other two classes of measurements we may cite: direction finding on individual atmospherics, or on signals of short duration, and studies of the polarization of waves or pulses.

In this chapter we shall concern ourselves with the oscilloscope itself. Applications of this instrument will be found at various places in the book, associated with the particular equipment under observation, test, or measurement.