Whitepaper
Becoming Familiar with your Standard Oscilloscope Probe
This Keysight application note details important considerations when using oscilloscope probes, specifically focusing on high-impedance passive probes commonly paired with oscilloscopes ≤1 GHz. It explains how a standard 10:1 probe works—utilizing a 9 MΩ tip resistance and 1 MΩ input impedance to achieve attenuation—and the importance of proper compensation via an adjustable capacitor to match oscilloscope input capacitance. The paper also explores dual-attenuation ratio (1:1/10:1) probes, like the Keysight N2140A/N2142A, demonstrating that while 1:1 mode reduces noise (showing a nearly 50% reduction in measured power supply ripple), it significantly limits bandwidth to ~25 MHz. Finally, it covers probe loading effects—resistive, capacitive and inductive—and their impact on measurement accuracy, emphasizing that capacitive reactance becomes dominant at higher frequencies and can cause ringing due to LC resonance.