“The mixed signal oscilloscope (MSO) has become everyone’s “engineering” Swiss army knife. Why does anyone need an additional logic analyzer? Now, the price of MSOs with sampling rates in the GHz range and 8 or more digital lines is well below US$3,000, and some are even less than US$1,000. Therefore, many people in the electronics industry have announced the elimination of logic analyzers as a stand-alone device.
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The mixed signal oscilloscope (MSO) has become everyone’s “engineering” Swiss army knife. Why does anyone need an additional logic analyzer? Now, the price of MSOs with sampling rates in the GHz range and 8 or more digital lines is well below US$3,000, and some are even less than US$1,000. Therefore, many people in the electronics industry have announced the elimination of logic analyzers as a stand-alone device.
Today, it is not surprising that mixed-signal oscilloscopes can be found in most electronic engineering laboratories. They are versatile, reasonably priced, and have become an essential tool for any engineer who tests, debugs, or verifies electronic systems. In fact, this may be the only instrument that most electronic engineers will have to use, or it may be used 90% of their laboratory time. Therefore, it is wise to spend part of the initial engineering or test laboratory budget on MSO. But does this mean that a logic analyzer (LA) is no longer needed?
Oscilloscope and logic analyzer
Digital oscilloscopes and logic analyzers are based on sampling technology. The measured value of the signal (usually voltage) is converted into a digital value by a high-speed analog-to-digital converter (ADC) and stored in the memory at a fixed time interval defined by the sampling clock of the instrument.
Think of a logic analyzer as an oscilloscope with 1-bit vertical resolution on all channels. It displays the signal as a logical (binary) value based on whether the measured voltage is higher or lower than a conventional voltage level called “threshold”. This is the first basic difference between an oscilloscope and a logic analyzer.
Another basic difference between an oscilloscope and a logic analyzer is the way the sampled value is displayed. In the most common mode of operation, an oscilloscope is essentially a device that can repeatedly capture an event window of a given length (defined by its total memory) and refresh a portion of its display on the Screen. Many oscilloscopes simulate “persistence” by superimposing multiple captured windows on the display and modulating the intensity of screen pixels.
The logic analyzer is mainly used for single capture (without overlapping continuous capture), and analyzes the sequence of events that sometimes exceed 100 digital signals before and after the trigger event.
The advent of microcontroller-based systems required the creation of tools such as logic analyzers. First, you need to look at the digital bus, so you need two or more channels. Second, you need to view the working mode of the logic circuit in the form of binary values, that is, the signal seen during the sampling event of the circuit. Over time, logic analyzers have evolved into “pure” instruments that can perform some analog measurements, such as checking threshold levels, detecting glitches, and verifying whether the signal meets certain input and output standards.
“Real time”, really?
It is very common to hear that the real-time display function is the main difference between an oscilloscope and a logic analyzer. In fact, automatic display refresh may make users mistakenly believe that they will see the data as it appears. However, the refresh rate of the oscilloscope display is not as fast as the eye actually sees. In most cases, the logic analyzer (LA) is used by first capturing the data and then analyzing it. The repeat trigger function of the logic analyzer can also refresh the display based on recurring trigger events. Indeed, the display and presentation of data in digital oscilloscopes and LA are different, but fundamentally speaking, these two tools operate by sampling the signal and storing the samples in memory.
MSO = oscilloscope + logic analyzer?
Well, mainly. Mixed signal oscilloscopes have analog channels (usually 2 to 4) and digital channels (usually 8 to 16). On these two types of channels, the data is sampled at the MSO’s maximum sampling rate (usually 1GHz). The sampling clock is usually generated internally by the MSO. In other words, the reference time base used for sampling is not related to the data. This is the so-called “timing analysis”. Of course, for digital channels, the vertical signal resolution of the logic analyzer is reduced to 1 bit.
MSO can perform certain functions traditionally reserved for LA:
The mixed signal oscilloscope (MSO) has become everyone’s “engineering” Swiss army knife. Why does anyone need an additional logic analyzer? Now, the price of MSOs with sampling rates in the GHz range and 8 or more digital lines is well below US$3,000, and some are even less than US$1,000. Therefore, many people in the electronics industry have announced the elimination of logic analyzers as a stand-alone device.
Today, it is not surprising that mixed-signal oscilloscopes can be found in most electronic engineering laboratories. They are versatile, reasonably priced, and have become an essential tool for any engineer who tests, debugs, or verifies electronic systems. In fact, this may be the only instrument that most electronic engineers will have to use, or it may be used 90% of their laboratory time. Therefore, it is wise to spend part of the initial engineering or test laboratory budget on MSO. But does this mean that a logic analyzer (LA) is no longer needed?
Oscilloscope and logic analyzer
Digital oscilloscopes and logic analyzers are based on sampling technology. The measured value of the signal (usually voltage) is converted into a digital value by a high-speed analog-to-digital converter (ADC) and stored in the memory at a fixed time interval defined by the sampling clock of the instrument.
Think of a logic analyzer as an oscilloscope with 1-bit vertical resolution on all channels. It displays the signal as a logical (binary) value based on whether the measured voltage is higher or lower than a conventional voltage level called “threshold”. This is the first basic difference between an oscilloscope and a logic analyzer.
Another basic difference between an oscilloscope and a logic analyzer is the way the sampled value is displayed. In the most common mode of operation, an oscilloscope is essentially a device that can repeatedly capture an event window of a given length (defined by its total memory) and refresh a portion of its display on the screen. Many oscilloscopes simulate “persistence” by superimposing multiple captured windows on the display and modulating the intensity of screen pixels.
The logic analyzer is mainly used for single capture (without overlapping continuous capture), and analyzes the sequence of events that sometimes exceed 100 digital signals before and after the trigger event.
The advent of microcontroller-based systems required the creation of tools such as logic analyzers. First, you need to look at the digital bus, so you need two or more channels. Secondly, it is necessary to view the working mode of the logic circuit in the form of binary value, that is, the signal seen during the sampling event of the circuit. Over time, logic analyzers have evolved into “pure” instruments that can perform some analog measurements, such as checking threshold levels, detecting glitches, and verifying whether the signal meets certain input and output standards.
“Real time”, really?
It is very common to hear that the real-time display function is the main difference between an oscilloscope and a logic analyzer. In fact, automatic display refresh may make users mistakenly believe that they will see the data as it appears. However, the refresh rate of the oscilloscope display is not as fast as the eye actually sees. In most cases, the logic analyzer (LA) is used by first capturing the data and then analyzing it. The repeat trigger function of the logic analyzer can also refresh the display based on recurring trigger events. Indeed, the display and presentation of data in digital oscilloscopes and LA are different, but fundamentally speaking, these two tools operate by sampling the signal and storing the samples in memory.
MSO = oscilloscope + logic analyzer?
Well, mainly. Mixed signal oscilloscopes have analog channels (usually 2 to 4) and digital channels (usually 8 to 16). On these two types of channels, the data is sampled at the MSO’s maximum sampling rate (usually 1GHz). The sampling clock is usually generated internally by the MSO. In other words, the reference time base used for sampling is not related to the data. This is the so-called “timing analysis”. Of course, for digital channels, the vertical signal resolution of the logic analyzer is reduced to 1 bit.
MSO can perform certain functions traditionally reserved for LA: