By far the most used oscilloscope probes are the passive 10:1 attenuation probe. Next step in probe categories are active probes.
Active probes succeed in practically eliminating reactive loading of the circuit under investigation by means of a small solid-state amplifier in the probe body adjacent to the tip.
There are two main classes of signals we electronics engineers care about: single-ended and differential-mode. With single-ended connection, the signal is carried on a single wire, which is defined as being referenced to the common system ground. Single-ended connection is usually quite easy to measure with normal oscilloscope probe. Differential-mode signalling uses a pair of wires, where the voltage difference between the wires forms the signal
Differential probes are oscilloscope probes designed to measure the difference between two signals. Differential probes allow a standard bench-type oscilloscope to be used to measure the voltage between two terminals. Both are referenced to but float above the electrical system ground potential. This cannot be done using a single-ended probe.
Differential probes are optimized to acquire only the differential signal between two test points, always reject (i.e. do not measure or display) any common mode signal. Early designs consisted of a pair of passive probes terminated at a differential amplifier located as a separate device adjacent to the oscilloscope Some modern scopes can calculate and display the difference without extra hardware. For probing differential signals, it is possible to use a pair of probes, one for each signal wire, and then utilise the scope’s math difference function to show the signal. This is quite often a desperate measure, and what you really want is a differential front-end in hardware. You need a differential active probe.
There are different differential probes for different applications. For fast digital signal measurements engineers need differential probes that can handle very fast signals at few volts amplitude. There are several brands of differential input oscilloscopes available. Differential signaling used in high speed serial standards requires very accurate characterization.
The engineers that need to measure mains voltage circuits and power supplies need differential probes that can handle voltages up to hundreds of volts. Because of the electrical environment within which they are used, differential probes in some applications are required to have higher voltage ratings, typically 600 V. Differential oscilloscope probe eradicates the problem of making accurate voltage waveform measurements on circuit elements that are not ground-referenced, without the risk of short circuits that could damage the device under test or the measuring instrument. These probes are the best choice for making non-ground referenced, floating or isolated measurements in large part due to their common mode rejection capability.
(#0032) High Voltage Oscilloscope Probe Design – DRSSTC vs. Spark Gap #04 – Modding a 1kV differential scope probe to measure 20kV