Summary
Every probe has inherent resistive, capacitive, and inductive loading that cannot be totally eliminated. Resistive loading affects voltage, capacitive loading affects timing, and inductive loading distorts the signal. There are many different oscilloscope probes (both passive and active) available designed to reduce loading. The passive probes are the low-impedance resistive divider probe, and the compensated high-resistance passive divider probe. The high-voltage probe is a special case of the compensated high-resistance passive divider probe. The active probes are either FET or bipolar probes. There is also the differential active probe. Each of these probes are designed to provide the best possible measurement for your application.To choose the proper oscilloscope probe, you must decide which parameter, either voltage or timing, is the most important. You should also have a good understanding of the equivalent circuit of the device under test. Finally, knowledge of the expected signal, particularly its rise time and spectral content, is important for understanding the potential effects of resistive, capacitive, and inductive loading. This knowledge will result in getting the best possible measurement.
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