
Chapter3 DigitizerBasics
©NationalInstruments Corporation 3-11 NI5102 User Manual
Figure3-8. ProbeCompensation Comparison
Active and Current ProbesYou can also useactive probes and current probes with digitizers
andDSOs.
Activeprobes, such as differential and field-effect transistor (FET) probes,
contain activecircuitry in the probe itself to reject noise and amplify the
signal. FET probes are useful for low-voltagemeasurements at high
frequenciesan d differentialprobes are noted for theirhigh common mode
rejection ration (CMRR) and nongrounded reference.
Instead of using a series resistance in the loop to measure current, current
probesmagnetically measure AC and/or DC current flowing in a conductor.
This lack of seriesresistance causes very little interference in the circuit
being tested.
ProbeAdjustment Signal ProbeAdjustment Signal Probe Adjustment Signal
ProperAmplitude of a
1MHz Test Signal
ReducedAmplitude of a
1MHz Test Signal
IncreasedAmplitude of a
1MHz Test Signal
a.Compensated Correctly b. Undercompensated c.Overcompensated