Oscilloscope Vs. Logic Analyzer

Maybe, you are planning to buy an oscilloscope but the logic analyzer also seems to suit your need. Due to budget, you only have one choice to choose from. All you have to do is to learn both of them first so that you know which one is really appropriate for your project.

Aside from that case, you may be studying the electronic testing instruments and wondering what things differ oscilloscopes from logic analyzers.

Here we do our best to let you get a clear explanation of the differences between the oscilloscope and logic analyzer.

The Core Differences

– Logic Analyzer

When working with digital circuits and signals, a logic analyzer can be a very handy tool. A logic analyzer allows its user to debug and verify digital systems by capturing the data into timing diagrams, assembly language, and state machine traces.

Just like a logic circuit, a logic analyzer displays the highs and lows of a digital circuit. The highs and lows are then plotted against time, these diagrams are known as timing diagrams. Logic analyzers trace the execution of embedded software and examine the efficiency of the program’s execution during software/hardware integration. Some logic analyzers associate certain hardware activities in your design with the source code.

When debugging a micro-processor-based design, a traditional oscilloscope does not provide enough input channels. A logic analyzer on average comes with 8 to 136 input channels depending on the preferred model.

Logic analyzers often have more channels than oscilloscopes and can show data in state mode, with one of the channels serving as a clock.

– Oscilloscope

One might argue that an oscilloscope offers way more features than a logic analyzer and they might not be wrong to some extent. An oscilloscope allows users to analyze signals and perform different mathematical functions on them. It can monitor both analog and digital signals, show ringing transient signals, analyze phase differences between two signals, and much more.

The Other Differences

The key difference between the two instruments has been stated a couple of times already in this article however there are other features that these instruments offer that do set them apart from each other.

– How They Capture Signals

An oscilloscope is continuously capturing varying signals and displays them on the screen, while a logic analyzer records the data first and then displays it on the screen. In other words, a scope shows the signals in real-time while a logic analyzer logs each reading and then displays the result at the end.

– What They Measure

Oscilloscope vs logic analyzer: Rigol DS1104Z Plus Oscilloscope showing amplitude of the signals
Rigol DS1104Z Plus Oscilloscope is showing the amplitude of signals

An oscilloscope measures the amplitude of signals against time, while a logic analyzer measures the time between the capture points. While some high-end scopes offer the FFT (Fast Fourier Transform) feature where it converts time-domain signals to frequency-domain signals for further analyses, a logic analyzer offers a protocol analyzer feature that is unique to a digital system allowing it to capture and monitor data over a communication channel.

– How They Work

Since both the devices are made for different purposes they don’t operate in the same way as well.

First, let’s talk about how a scope (oscilloscope) measures a reading. It starts with probing a circuit with the provided probes, the tip of the probe is kept on the point of interest and the ground clip that comes mounted on the probe is attached to the ground of the circuit that is being tested. The measured signal is then picked by a signal amplifier within the circuitry of the oscilloscope which then amplifies the signal to a considerable value. Since an oscilloscope is a digital device, it requires an Analog to Digital Converter or ADC for short. The ADC performs sampling on the input signals and converts the voltages into digital information. The sampled data from the ADC is then stored and used to construct a close approximate image of the captured signal.

Just like an oscilloscope, a logic analyzer also comes with probes that allow users to debug and analyze different sections of a digital circuit. When sampling a signal some logic analyzers allow users to select the type of clock that they want to use. A logic analyzer compares its two signals using a comparator which is not something an oscilloscope does. The way a comparator works is that if the voltage level is higher than a set threshold value the output signal will be high or 1, if the input signal is lower than the threshold value the output signal will be low or 0. Since a logic analyzer does not have an ADC (Analog to Digital Converter), it has many input channels.

– Triggering Feature

A logic analyzer offers more triggering features than an oscilloscope. Many oscilloscopes allow their users to either select the internal or external signal to trigger the sweep that displays the captured waveform. In a logic analyzer, all of the probed channels can be used to trigger the start of capture.

– Form Factor; How They Look Like

Talking about the form factor both the oscilloscope and logic analyzers come in a variety of different sizes. A more recent desktop oscilloscope may be more compact compared to a logic analyzer which usually is very bulky. Both oscilloscope and logic analyzers do have handheld and PC USB-based variants offering limited features when compared to a standalone desktop version. Since both offer unique features it is always cheaper for an individual to buy an oscilloscope compared to a logic analyzer which is very expensive and is only used when designing a digital circuit.

Last Thought

Both oscilloscopes and logic analyzers have their pros and cons but in the end, it mostly comes down to the requirements and preferences of an individual.

For someone that designs digital circuits that requires a processor, a logic analyzer can be a great and handy tool without one it’s going to be a nightmare understanding the timing diagrams and logic of a circuit.

On the other hand, for someone who is a hobbyist or does not work on designing processor-based circuits, an oscilloscope is a great tool. An oscilloscope will not only let its users analyze signals and behavior of systems, but it also allows them to manipulate them through different mathematical and complex functions. For a beginner starting in the world of electronics, it is always recommended to own an oscilloscope to help visualize the abstract world of electricity.

Another Solution

A mixed-signal oscilloscope (MSO) is also an option for someone needing both an oscilloscope and a logic analyzer, to save space on your precious workbench. However, they don’t always come cheap and are very expensive for an individual/hobbyist to own. A mixed-signal oscilloscope (MSO) captures and displays both analog and digital signals. It has channels for an oscilloscope as well as dozens of digital inputs. MSO’s are mostly used by professional engineers in the industry who require both instruments.