Probing Techniques and Tradeoffs (Part VII): More on Dynamic Range

Figure 1: Input offset range is how much
differential offset a probe can apply to
an input signal to bring it within its
differential-mode output range

In our last post in this series, we'd begun discussing the third of three types of dynamic range as applied to probes, and that is input offset range. This is the maximum differential offset that a probe can apply to the input signal to bring it within the probe's differential-mode dynamic range.

Probing Techniques and Tradeoffs (Part VI): Dynamic Range

Figure 1: Differential-mode dynamic range is the maximum
allowable voltage between the probe amplifier's inputs

We've been discussing probe loading, which is the unavoidable reality of what happens when you attach an oscilloscope probe to a live circuit. We'll now shift the discussion to dynamic range, an important topic that can be overlooked when selecting an oscilloscope probe. There are three types of dynamic range that one should understand. Each of them will influence how you set up your probe and how you set up your signal under test to most effectively get that signal into the oscilloscope's front-end amplifier.

Back to Basics: Differential Probing

Figure 1: Emitter voltage measurement
in simplified schematic view

Whether or not we think of it in such terms, any voltage measurement taken with an oscilloscope or voltmeter is, in reality, a differential voltage measurement. A voltage is, by definition, the difference in electrical potential between two points in a circuit. It's impossible to take a voltage measurement with only one voltmeter lead. One lead must be attached to the point of interest while the other must be connected somewhere else as a reference point.