What are the common measurement methods for differential signals with differential probes?

There are many types of probes. Differential probes are very common in switching power supply applications. Antai Test will focus on the measurement of differential signals and explain in detail the common measurement methods of differential signals with differential probes.

There are three common measurement methods with differential probes: The first is to use two probes to make two single-ended measurements: This is a common method and the least desirable method for making differential measurements. The differential signal can be measured by measuring the signal to ground (single-ended) and using the oscilloscope's math function (channel A signal minus channel B). This approach can be used when the signal is low frequency and the amplitude of the signal is large enough to exceed any concerns about noise.

The second differential probe measurement method is oscilloscope floating measurement: the current common erroneous floating measurement method is the oscilloscope floating measurement method, which is to cut off the ground wire of the standard three-prong AC socket or use an AC isolation transformer to cut off the neutral line and Ground connection. Float the oscilloscope away from the protective ground wire to reduce the impact of ground loops. This method is actually not feasible because the neutral wire may have been connected to the ground somewhere in the wiring of the building, which is an unsafe measurement method; in addition, it violates industrial health and safety regulations, and the measurement results obtained are also unsafe. Difference.

Three common measurement methods for differential probes: Differential measurement: A better solution for floating measurement is to use a differential probe with a high common mode rejection ratio, because there is no grounding problem at both input ends, and the differential operation of the two input signals After the probe front-end amplifier is completed, the signal transmitted to the oscilloscope channel is the differential voltage. The oscilloscope can achieve safe floating measurements without removing the ground end of the three-wire plug.

Compared with traditional probes, differential probes have superior performance and smaller signal interference when used in oscilloscope measurements.