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Chapter 3 Digitizer Basics
© National Instruments Corporation 3-11 NI 5102 User Manual
Figure 3-8. Probe Compensation Comparison
Active and Current Probes
You can also use active probes and current probes with digitizers
and DSOs.
Active probes, such as differential and field-effect transistor (FET) probes,
contain active circuitry in the probe itself to reject noise and amplify the
signal. FET probes are useful for low-voltage measurements at high
frequencies and differential probes are noted for their high common mode
rejection ration (CMRR) and nongrounded reference.
Instead of using a series resistance in the loop to measure current, current
probes magnetically measure ACand/or DC currentflowing ina conductor.
This lack of series resistance causes very little interference in the circuit
being tested.
Probe Adjustment Signal Probe Adjustment Signal Probe Adjustment Signal
Proper Amplitude of a
1 MHz Test Signal
Reduced Amplitude of a
1 MHz Test Signal
Increased Amplitude of a
1 MHz Test Signal
a. Compensated Correctly b. Undercompensated c. Overcompensated