A spectrum analyzer measures the magnitude of an input signal versus frequency within the full frequency range of the instrument. The primary use is to measure the power of the spectrum of known and unknown signals. The input signal that most common spectrum analyzers measure is electrical; however, spectral compositions of other signals, such as acoustic pressure waves and optical light waves, can be considered through the use of an appropriate transducer. Spectrum analyzers for other types of signals also exist, such as optical spectrum analyzers which use direct optical techniques such as a monochromator to make measurements.
A spectrum analyzer from 2005
A modern real time spectrum analyzer from 2019
A spectrum analyzer circa 1970
The main PCB from a 20 GHz spectrum analyser. Showing the stripline PCB filters, and modular block construction.
An oscilloscope is a type of electronic test instrument that graphically displays varying voltages of one or more signals as a function of time. Their main purpose is capturing information on electrical signals for debugging, analysis, or characterization. The displayed waveform can then be analyzed for properties such as amplitude, frequency, rise time, time interval, distortion, and others. Originally, calculation of these values required manually measuring the waveform against the scales built into the screen of the instrument. Modern digital instruments may calculate and display these properties directly.
A Tektronix model 475A portable analog oscilloscope, a typical instrument of the late 1970s
Oscilloscope cathode-ray tube, the left square-shaped end would be the blue screen in the upper device when built in.
Typical display of an analog oscilloscope measuring a sine wave signal with 10 kHz. From the grid inherent to the screen together with the user-set parameters of the device shown at the upper display rim, the user may calculate the frequency and the voltage of the measured signal. Modern digital oscilloscopes set the measurement parameters and calculate/display the signal values automatically.
Type 465 Tektronix oscilloscope. This was a popular analog oscilloscope, portable, and is a representative example.