As highlighted above in the article, an oscilloscope measures signals in the time domain while a spectrum analyzer captures and measures signals in the frequency domain.
In the previous article, we have discussed the differences between oscilloscopes and logic analyzers. In this post, we are going to differentiate another electronic testing instrument spectrum analyzer from oscilloscopes. This article hopefully helps you know which instrument to use when it comes to designing a certain circuit (RF, analog, and digital).
For an electrical engineer, an oscilloscope is a vital testing instrument capable of measuring voltage signals in the time domain. An oscilloscope is typically used when designing or debugging a circuit. It allows users to analyze how their circuit is behaving when a certain input voltage is applied. Unlike a digital multi-meter, an oscilloscope plots a series of continuous waves to show the output response of an electrical system.
To analyze signals simply probe the part of the circuit that you want to analyze. An oscilloscope usually comes with an LCD screen allowing users to see and interact with the signals being analyzed. Just by probing the point of interest on the circuit, a user can easily measure the amplitude, frequency, peak-to-peak voltage, and other relevant information.
Mathematical functions such as addition, multiplication, subtraction, division, derivation, and integration can also be implemented on the signals and they can be measured and displayed.
An average oscilloscope usually comes with 2 channels for the probes to connect to, allowing users to measure two different signals at the same time. Check our top 10 selected oscilloscopes as they come at least with 2 channels. It’s always recommended to have at least 4 channels on an oscilloscope, you may never know when you might need to analyze more than 2 signals at once.
– Spectrum Analyzer
For measuring signals in the frequency domain, a spectrum analyzer is used. Even though some high-end oscilloscopes do come with the FFT feature (Fast Fourier Transform) allowing users to view the signals in the frequency domain. Due to the limited bandwidth of an oscilloscope, a standalone spectrum analyzer is preferred as it offers higher bandwidth making it easy for users to observe high-frequency signals.
A spectrum analyzer is typically used in the Radio-Frequency industry where RF circuits such as transmitters and receivers are designed. It is also used in the designing of amplifiers, filters, oscillators, mixers, etc. The main purpose of a spectrum analyzer is to measure noise, power, amplitude, frequency response, and distortion in RF and audio circuits. A spectrum analyzer is capable of measuring signals in the microwave region of the electromagnetic spectrum.
So, what is the core difference?
When comparing both an oscilloscope and a spectrum analyzer, one should keep in mind that it’s not an apples-to-apples comparison however, there are key differences between the two. As highlighted above in the article an oscilloscope measures signals in the time domain while a spectrum analyzer captures and measures signals in the frequency domain.
Real-Time Bandwidth Comparison
Talking about the Real-Time bandwidth that determines how a device performs in ultra-wide signal analysis, an oscilloscope performs better than a spectrum analyzer.
An oscilloscope measures a bandwidth using the frequency range that it offers which is more useful for real-time sampling ranging from Mega to Gigahertz, while a spectrum analyzer can measure bandwidth in a few Megahertz ranges depending on the model of the device. Check these top 10 spectrum analyzers and see their frequency range. An oscilloscope can measure multiple signals at a time while a spectrum analyzer has a local oscillator that decides which frequency to observe at a given time.
The dynamic range of a device is basically its ability to differentiate between maximum and minimum signals at the input. For a spectrum analyzer, the ideal dynamic range is approximately 90 decibels while for an oscilloscope the dynamic range is approximately 50 decibels, making spectrum analyzers more superior to oscilloscopes.
Limited by its own processing ability and bandwidth limitations, an oscilloscope can measure low-frequency signals at a very slow speed. Unlike oscilloscopes, a spectrum analyzer is designed for measuring signals ranging from low all the way to microwave range. A spectrum analyzer offers a spectrogram and waterfall display features. A spectrogram visually represents the signal strength over time at a different range of frequencies while a waterfall display feature shows the signal power over time at different ranges of frequencies.
An oscilloscope provides users with a user-friendly and easy-to-use UI (User Interface), allowing new users and occasional electronics hobbyists to use it with ease. So, it’s quite intuitive. On contrary, a spectrum analyzer is an instrument that only someone with a technical background such as engineers and technicians can use. It has some complex functions that an average tinkerer would find difficult to use and understand. While both the instruments do have a learning curve, an oscilloscope is a clear winner when it comes to ease of use right out of the box to get the user going.
Oscilloscope and Spectrum Analyzers offer an input impedance of 1MΩ or depending on the model purchased. Higher impedance makes both instruments sensitive to noise. Talking about the sensitivity, an oscilloscope is more sensitive to signal changes at its capable of measuring signals at 1mV/division.
Both devices are available in different form factors e.g.: desktop, handheld, and USB scopes/analyzers. The USB models allow the users to employ their computers to interact with the instrument. With the latest models of oscilloscopes, the line between a scope and a spectrum analyzer has been blurred. Since most of the features that a spectrum analyzer offers are being readily made available in an oscilloscope.
However, the scope (oscilloscope) that offers all the features of a spectrum analyzer as well as oscilloscope charges you with a hefty price tag. Surely, it makes it difficult for some individuals to own. Both the equipment allow users to transfer their captured signals using a USB stick and transfer them to their PC for further analysis and manipulation.
Finally, both instruments provide a user with the ability to measure signals in a circuit and analyze their behaviors. From an engineer’s point of view, both instruments are critical when testing and designing.
If a user works in the RF industry that designs antennas, transmitters, receivers, and other types of communication devices, a spectrum analyzer is a must-have instrument.
While a user that designs power conversion circuits, amplifiers, and digital circuits an oscilloscope is a perfect tool for testing.
For a beginner or a tinkerer, an oscilloscope provides more than enough features required to design and debug low-level circuits. It provides users with enough information about their circuits to get them started within the world of electronics by providing a solid foundation and experience to move further to more complex instruments such as a spectrum analyzer.