How to choose the appropriate oscilloscope probe for power supply ripple testing?
1 How to check the range of oscilloscope probe?
The measuring range of oscilloscope probes generally has a maximum voltage of 300Vrms for passive probes. The measuring range of high-voltage probes or differential probes can be found in the specification book according to the model. The measuring ranges under different attenuation ratio gears are different. When used, the maximum allowed input voltage is determined based on the current gear.
2 What should I do if the oscilloscope probe tip is broken?
Today's probes are generally equipped with a spare probe. Use pliers to remove the broken probe in the direction and replace it directly. If you do not have spare probes, you can ask your local dealer for original accessories.
3. What should I do if the noise floor measured by the oscilloscope probe is too large?
After connecting the probe to the oscilloscope, you can see that the waveform on the oscilloscope is noisy, which is normal. This is because a closed loop is not formed and coupled into the space noise. Closely connect the positive end of the probe to the ground wire, and you can see the current true noise floor.
Generally, if the noise is too loud during the measurement process, you can remove the ground wire and use a ground spring to measure, especially high-frequency signals.
4. What should I do if the signal measured by the oscilloscope probe overshoots and oscillates obviously?
If there is obvious overshoot or oscillation on the rising edge of the measurement signal, it is usually caused by the ground wire being too long. Changing a ground spring can eliminate this effect and measure the true signal rise characteristics.
5. What is the reason why the voltage measured by the probe is inaccurate?
If the voltage measured by the probe is not accurate, please first check whether the attenuation ratio of the probe is consistent with the setting in the oscilloscope. Secondly, consider the load effect of the probe. If the output impedance of the circuit under test is large, then ordinary passive probes cannot measure it and must be replaced with active probes. Probes (active single-ended/differential probes), this is a problem caused by impedance voltage division.
6 How to choose a suitable oscilloscope probe for power supply ripple testing?
For power supply ripple testing, it is best to use a high-impedance passive probe at 1X level. The advantage is that it does not require internal amplification of the oscilloscope, has low noise, and has a high signal-to-noise ratio. Use the ground spring as the ground wire during measurement, set the bandwidth limit of the oscilloscope to 20MHz, and select the channel coupling to AC coupling as needed, so that you can observe low-frequency small signal measurements such as power supply ripple.
