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Notes on the use of oscilloscope probes

The first is bandwidth, which is usually written on the probe, how many MHz. If the probe's bandwidth is not enough, the oscilloscope's bandwidth is high, it is useless, bottleneck effect.
The other is the impedance matching of the probe. The probe should be adjusted for its impedance matching before use. Usually there is a tunable capacitor on the probe near the end of the oscilloscope, and some probes have adjustable capacitance near the end of the probe. They are used to adjust the impedance matching of the oscilloscope probe. If the impedance does not match, the measured waveform will be distorted.

oscilloscope current probe
oscilloscope current probe
oscilloscope probe
oscilloscope probe

 
When the oscilloscope probe is in use, make sure that the ground wire clip is reliably grounded (the ground of the system under test, not the real earth). Otherwise, when measuring, you will see a large 50Hz signal. This is because the oscilloscope The ground wire was not connected, but it was generated by sensing the 50 Hz power frequency mains in the space. If you find a very strong 50Hz signal on the oscilloscope, you should pay attention to see if the probe's ground wire is not connected. Due to the frequent use of oscilloscope probes, grounding may be broken. The detection method is: adjust the oscilloscope to the appropriate scanning frequency and Y-axis gain, then touch the probe in the middle of the probe by hand, then you should be able to see the waveform, usually a 50Hz signal. If there is no waveform at this time, you can check if the signal line in the middle of the probe is damaged.


The ground clamp of the oscilloscope probe should be close to the measurement point, especially when measuring signals with higher frequency and smaller amplitude. Because of the long ground wire, a ring is formed, which is like a coil that senses the electromagnetic field of the space. In addition, when the current in the ground in the system is large, the voltage drop will also occur on the ground line, so the ground wire of the oscilloscope probe should be connected to the ground near the test point.

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