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Keysight Oscilloscope Glossary

What Is Trace in Oscilloscopes?

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Did you know that the term "trace" in oscilloscopes originated from the days when phosphor screens displayed the waveform, creating a visual trace? 

Even in today's digital age, understanding what a trace is and how to analyze it remains a cornerstone of electrical engineering work involving oscilloscopes. 

Whether you're debugging a circuit or analyzing signal integrity, a deeper understanding of traces can significantly elevate your work.

What is a Trace?

A trace serves as a graphical representation of an electrical signal against time or another relevant parameter, displayed on an oscilloscope screen. In essence, it "traces" the behavior of a signal.

Components of a Trace

A typical trace consists of the following elements:

  1. Amplitude: Represents the voltage level.
  2. Time: Horizontal axis showing the time domain.
  3. Trigger point: A specified voltage or time event that starts the trace.

 

Key Takeaway
Understanding the intricacies of traces in oscilloscopes is essential for accurate signal analysis and effective troubleshooting. Mastering different types of traces, calibration techniques, and advanced features like signal processing can significantly enhance your diagnostic and testing capabilities.

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Types of Traces

Understanding the various types of traces in an oscilloscope empowers engineers to select the most suitable mode for a given application. Let's delve into four common types of traces: Single Trace, Dual Trace, Math Trace, and XY Trace.

Single Trace

A single trace displays one waveform derived from a single input channel. This is the most straightforward type of trace and is often the starting point for many diagnostic activities.

Applications

  • Basic troubleshooting
  • Signal integrity checks
  • Time-domain measurements

Advantages

  • Simplified view for quick diagnosis
  • Easy to set up and calibrate
  • Ideal for less complex signal structures

Limitations

  • Can’t compare multiple signals simultaneously
  • Limited in analyzing interactions between channels
     

Dual Trace

Dual trace enables the simultaneous display of two waveforms, each coming from separate input channels. This capability is crucial for comparative analyses and for studying signal interactions.

Applications

  • Phase comparison
  • Differential measurements
  • Simultaneous monitoring of input and output signals

Advantages

  • Enables direct signal comparison
  • Useful for cause-and-effect analysis
  • Saves time by showing two signals simultaneously

Limitations

  • May require more complex triggering setups
  • Risk of display clutter with intricate waveforms
     

Math Trace

A math trace doesn't rely solely on direct input but calculates and displays a waveform based on a mathematical operation or function applied to one or more input channels.

Applications

  • Signal filtering
  • Complex computations like Fourier transforms
  • Creating derived parameters for analysis

Advantages

  • Offers advanced analysis capabilities
  • Allows custom equations for specific needs
  • Enables investigation of signals in the frequency domain

Limitations

  • May require familiarity with mathematical functions
  • Potential for computational errors if incorrectly set up

XY Trace

In XY trace mode, the oscilloscope plots one channel's voltage against another channel's voltage, as opposed to plotting against time. This results in a Lissajous figure and is useful for phase and harmonic analysis.

Applications

  • Phase relationship studies
  • Harmonic distortion analysis
  • Quality control for signal generators

Advantages

  • Provides a quick view of phase relationships
  • Allows detailed harmonic analysis
  • Useful for specialized tests like hysteresis loop characterization

Limitations

  • Lacks time-domain information
  • May require expertise for correct interpretation

By understanding these four main types of traces, you can more effectively choose the right oscilloscope settings for your specific engineering tasks. Each type offers unique advantages and limitations that can greatly impact the success of your measurement and analysis.
 

How to Read a Trace

Accurately reading and interpreting a trace is an essential skill for electrical engineers and professionals using oscilloscopes. 

This section will expand on crucial steps such as calibration, identifying key points, and utilizing cursors for precise measurements.

Calibration

Calibration ensures that the oscilloscope accurately measures and displays electrical signals. Minor drifts in the device's internal components over time can cause inaccurate readings, so regular calibration is necessary.

Steps for Calibration

  1. Connect a calibration signal to the oscilloscope's input.
  2. Follow the oscilloscope’s calibration procedure, which usually involves adjusting gain and offset settings.
  3. Confirm that the displayed trace accurately represents the calibration signal.

Common Calibration Errors

  • Incorrect probe attenuation
  • Mismatch between the oscilloscope and probe impedance

Identifying Key Points

Zero Level
The zero level serves as the midpoint around which the waveform oscillates. It represents the "zero voltage" point and is crucial for determining the signal's amplitude and other metrics.

Peak Levels
Peak levels are the highest and lowest points the waveform reaches. Understanding peak levels helps you:

  • Evaluate signal strength
  • Detect potential clipping or saturation in the circuit
  • Determine the operating voltage range

Cycle
A cycle refers to one complete oscillation of the waveform. Recognizing the start and end points of a cycle helps you to:

  • Calculate the frequency of the signal
  • Assess periodicity and stability
  • Analyze any irregularities like jitter or noise

Utilizing Cursors

Cursors are graphical lines or markers that you can position on the trace for precise measurements. Modern oscilloscopes usually offer both horizontal and vertical cursors.

How to Use Cursors

  1. Activate the cursor function on your oscilloscope.
  2. Position the cursors at desired points on the trace.
  3. Read the measurement results, usually displayed on the side or bottom of the screen.

Benefits of Using Cursors

  • Facilitate exact measurements like rise time, fall time, and pulse width.
  • Enable delta measurements between two points, useful for phase and timing differences.
  • Simplify capturing and recording specific trace values for further analysis.

By mastering the steps of calibration, key point identification, and cursor utilization, you can ensure that you're reading traces accurately and obtaining meaningful data from your measurements. These skills are fundamental for anyone aiming to excel in tasks involving oscilloscopes.

 

Common Trace Artifacts

ArtifactCauseSolution
NoiseExternal interferenceUse shielding or filters
JitterTiming inconsistenciesIncrease sampling rate (in digital oscilloscopes)
GhostingResidual phosphor glow (in analog oscilloscopes)Adjust persistence settings

Tips for Analyzing Traces

Accurate and insightful trace analysis can make or break your work with oscilloscopes. Whether you're troubleshooting a faulty circuit or studying intricate signal behaviors, effective trace analysis techniques can greatly enhance your understanding. Here's a deeper look into some key tips for optimal trace analysis.

Use Appropriate Scaling

The vertical and horizontal scales are fundamental to how well you can visualize and interpret a trace. Incorrect scaling can lead to misinterpretation of the signal's characteristics.

Steps for Optimal Scaling

  1. Adjust the vertical scale to fit the trace within the screen, maximizing the trace amplitude without clipping.
  2. Set the horizontal scale to display at least one full cycle of the waveform, if applicable.

Consequences of Poor Scaling

  • Clipped peaks: Obscure the real amplitude of the signal.
  • Over-compressed trace: Makes it difficult to observe vital details.

Apply Signal Processing

Many modern oscilloscopes come with built-in signal processing features like filtering, averaging, and Fast Fourier Transform (FFT).

How to Apply FFT

  1. Select the FFT function in the menu.
  2. Choose the appropriate window function (Hanning, Blackman, etc.).
  3. Observe the frequency components displayed alongside or over the time-domain trace.

Benefits of Signal Processing

  • Uncover hidden signal characteristics: Signal processing can reveal aspects not visible in the time-domain view.
  • Reduce noise: Tools like averaging can help in eliminating random noise, offering a cleaner signal for analysis.

Check Trigger Settings

The trigger settings define the point at which the oscilloscope starts capturing the waveform. Incorrect triggering can lead to unstable or misleading traces.

Common Trigger Types

  • Edge triggering: Initiates the trace when the signal crosses a specified voltage level.
  • Pulse triggering: Starts the trace based on the duration of a pulse.
  • Frequency triggering: Activates the trace capture at a particular frequency.

Tips for Correct Triggering

  • Use auto-trigger for stable, repetitive signals.
  • Opt for normal or single-shot triggering for non-repetitive or complex signals.

By giving proper attention to scaling, utilizing signal processing features, and scrutinizing your trigger settings, you can vastly improve the quality and reliability of your trace analysis. 

These best practices help you extract maximum information from the oscilloscope traces, making your testing and diagnostic tasks more accurate and insightful.

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Conclusion

Traces are the heart of oscilloscope analysis, offering a detailed visual snapshot of electrical signals in action. They serve as a crucial tool for engineers in a myriad of applications—from simple troubleshooting to complex signal behavior studies. 

By mastering techniques like proper scaling, signal processing, and triggering, professionals can unlock the full potential of their oscilloscopes. 

Understanding the nuances of different types of traces and how to read them accurately elevates the quality of your work and leads to more meaningful insights.

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This article is brought to you by the Keysight Used Equipment Store. The information applies to used and new equipment.

If you know which Keysight model is of interest to you and matches your technical requirements, visit the Used Equipment Store to see if you can save with our offers.
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For more Test and Measurement knowledge and tips, view all technical articles. Visit our resources
Keysight assumes no liability for the completeness, correctness and accuracy of all content on this website and all of its content. Please read here the terms of use of this website.