Secrets of the 10x Passive Probe

Figure 1: The 10x passive probe
becomes a better measurement
tool when we understand its
limitations

We began this series of posts on oscilloscope probes by putting them in perspective: Probes have a number of different jobs to do, including serving effectively as both a mechanical and electrical interface. Despite having electrical attributes of their own, we want them to grab our signal of interest, but we don't want them to affect that signal in any way.

Putting Probes in Perspective

Figure 1: Probe, cable, and oscilloscope form a system
that makes or breaks the accuracy of signal acquisitions

Few aspects of using an oscilloscope are as important as the probe: after all, the probe forms both the mechanical and electrical interfaces between the device under test (DUT) and the oscilloscope itself. To feed a signal into an oscilloscope, we're limited to a coaxial connection. Thus, we need a geometry transformer that picks up the signal of interest from the DUT and transfers it to the oscilloscope's coaxial connection.