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P6330 3.5 GHz Differential Probe Instructi on Manual
19
Reference
This section contains important reference information about
differential measurements and how to increase the accuracy of your
measurements.
Problems with Single-Ended Measurements
While suitable in many applications, single-ended measurements can
present problems in the following situations:
H When the signal is not referenced to earth ground
H When the signal being measured is distorted or changed by
connecting or disconnecting the probe ground reference lead
Differential Measurements
Devices designed to make differential measurements avoid the
problems posed by single-ended systems. These devices include a
variety of differential probes, differential amplifiers, and isolators.
The differential amplifier (Figure 9) is at the heart of any device or
system designed to make differential measurements. Ideally, the
differential amplifi er rejects any voltage that is common to the inputs
and amplifies any difference between the inputs. Voltage that is
common to both inputs is often referred to as the Common-Mode
Voltage (V
CM
) and voltage that is different as the Differential-Mode
Voltage (V
DM
).