App-1
IM 701923-01E
Appendix—Probing
The speed of devices and electronic circuits that are incorporated into a variety
of products, as exemplified by digital home electronics, is increasing, and
oscilloscopes and probes used to observe their signal waveforms are also faster
and have wider bandwidths.
When the speed of the measured signal increases, there are cases when
correct measurements cannot be taken due to problems that have never
occurred before, especially in probing. This chapter explains issues that need to
be considered when probing high-speed signals.
Voltage Probe Types
A Voltage probes is a type of voltage sensor. The ideal probe should be selected
according to the signal’s voltage, output impedance, frequency components,
and other factors. The input impedance (resistance and capacitance) and
frequency can differ greatly depending on the type of probe. So, it is essential
to understand the characteristics of the available probes to obtain highly
reliable measurements. Below are three examples of probes generally used for
measurements on high-frequency circuits.
Passive Probes
Passive probes with a 10:1 attenuation ratio are the most widely used due to
their low cost, ruggedness, high withstand voltage, and high input impedance at
DC and low frequencies.
Yokogawa’s standard 10:1 passive probes are easy-to-use for general
applications. Their input impedance is 10 M
Ω
and approximately 14 pF
in parallel, and the withstand voltage is 600 V. However, the 14 pF input
capacitance might cause problems when high frequencies are measured.
PB500
500-MHz Passive Probe
