In this chapter, the important signals for use in frequency response tests are considered. As described in the previous chapter, Fourier analysis can be used to obtain frequency response information from nonsinusoidal tests that use periodic or nonperiodic input disturbances. We restrict our atten­tion to those currently known test signals that are practical to input with standard reactor hardware and that have power spectra that can give results over frequency ranges of interest. Discrete-level inputs (those that have only distinct values—usually two or three) are available that have the desired characteristics. In this chapter we consider the following discrete-level, periodic signals: pseudo-random binary sequence, n sequence, pseudo­random ternary sequence, multifrequency binary sequence and square wave. The nonperiodic signals considered are the pulse and the step.

In a frequency response test on a nuclear reactor, one of these signals could be used as an input to the system. The input and selected output sig­nals would then be analyzed using one of the methods described in Chapter 4 to give the frequency responses. The information in this chapter can aid the experimenter in selecting the test signal that is best suited for his application.