How to measure ripple voltage using oscilloscope

Ripple voltage measurement using oscilloscope
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Measuring ripple voltage accurately is essential for any technician or engineer working with electronic circuits. This article delves into the specifics of using an oscilloscope to measure the undesired remaining AC components within the DC output voltage of a power supply. Understanding ripple voltage and its potential impact on electronic systems is crucial, as it can often be a telltale sign of underlying issues within your power supply. Utilizing an oscilloscope for this task offers precision and a graphical representation that makes identifying problems with ripple voltages more intuitive. By the end of this guide, you will be well-equipped with the knowledge to effectively measure and interpret ripple voltages in your circuits, ensuring optimal performance of your power supply.

Understanding the Basics of an Oscilloscope

An oscilloscope is a powerful tool that allows technicians and engineers to observe the changing signal voltages, providing a visual representation of the waveforms. It operates by plotting an input voltage on the vertical axis against time on the horizontal axis, revealing how the voltage within a circuit fluctuates over time. There are various types of oscilloscopes – from the traditional analog scopes to digital storage oscilloscopes (DSOs). Digital types are preferred for measuring ripple voltage due to their ability to capture and store digital waveforms for analysis. An essential feature for ripple voltage measurement is the ability to observe lower-frequency fluctuations superimposed on the DC voltages that are typical in power supplies.

 Techniques for measuring ripple voltage with oscilloscope

Setting Up Your Oscilloscope for Ripple Voltage Measurement

When preparing to measure ripple voltage, setting up your oscilloscope properly is a key initial step. Start by ensuring your oscilloscope has a clean and calibrated signal path. Then, select the appropriate voltage range and time division settings to precisely capture the ripple voltages you expect out of your power supply. This might involve zooming in on the vertical scale to view the small ripples superimposed on the output voltage. Probes should be high-impedance and matched to the input impedances of the oscilloscope to prevent loading the circuit being tested.

Here are some vital steps to follow:

  1. Connect the oscilloscope ground lead to your circuit’s ground.
  2. Attach the probe to the output capacitor of your power supply.
  3. Adjust the oscilloscope settings for optimal viewing, which includes setting the trigger mode and voltage scales.
  4. Ensure that the probe compensation is adjusted correctly to avoid distorted signals.

The Measurement Process

With your oscilloscope set up, begin the measurement process by probing the points of interest in your circuit. When the oscilloscope captures the waveform, inspect the output for any rippled voltage. The amount of ripple can be determined by the peak-to-peak voltage measurement function found in most oscilloscopes. Watch out for common pitfalls, such as confusing noise with actual ripple or overlooking ripples at higher frequencies which might be filtered out by the bandwidth limit of the oscilloscope.

 Illustration of ripple voltage measurement via oscilloscope

Analyzing the Results

Once you have captured the ripple voltage on your oscilloscope, analyzing the data is the next critical step. The readout will show you the magnitude and frequency of the ripple present in the DC output. Typically, you would look for a steady, repetitive pattern indicating the ripple. A good ripple voltage is low enough not to interfere with the operation of the electronic device. However, if the level is too high, it could suggest issues with the power supply’s output capacitors or other components.

Troubleshooting Common Issues

If you encounter issues while measuring ripple voltage, don’t fret. Common challenges include unclear signals or unexpectedly high ripple voltages. To troubleshoot, revisit your setup and check if all connections are secure, and ensure no external noise sources could be influencing your measurements. Also, consider if the ripple is sourced from the power supply itself or is it induced from nearby switching power circuits or other electrical interference.

Advanced Tips for Professionals

For professionals looking for more precision in their measurements, here are advanced tips to consider:

  1. Utilize active probes for sensitive or high-frequency measurements – these can provide better fidelity at higher frequencies.
  2. Engage averaging functions on your oscilloscope to smooth out random noise and get a clearer picture of the ripple.
 Accurate ripple voltage assessment using oscilloscope


Ripple voltage is an important parameter that should be measured to ensure the integrity and reliability of electronic circuits. As we’ve discussed, oscilloscopes are indispensable tools for this task, providing detailed insight into the performance of power supplies. Accurate measurement and interpretation of ripple voltages using an oscilloscope can help diagnose problems and prevent damage to sensitive components. This guide has equipped you with the foundational knowledge needed to measure ripple voltage effectively. Armed with this information, you can ensure that your power supply maintains its output within the necessary performance parameters.

Frequently Asked Questions (FAQs)

What is ripple voltage and why is it important to measure?Ripple voltage refers to the residual periodic variation of the DC voltage within a power supply after being rectified and smoothed. Measuring ripple voltage is crucial because it can affect the performance and longevity of electronic components.
Can all types of oscilloscopes measure ripple voltage?Most digital storage oscilloscopes (DSOs) can be used to measure ripple voltage, but it’s essential they have the necessary bandwidth and sensitivity settings for accurate observation.
How do I choose the correct probe for measuring ripple voltage?For general measurements, use a high-impedance, passive voltage probe. For more sensitive or high-frequency applications, consider using an active probe.
What are the typical causes of excessive ripple voltage?Common causes include inadequate filtering, worn out or faulty capacitors, overload on the power supply, or improper operation of the rectifier.
Where in the circuit should I connect the oscilloscope probe to measure ripple voltage?The oscilloscope probe should be connected across the output terminals of the power supply, directly where the DC voltage is available, ensuring minimal ground lead length to avoid additional noise and interference.