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To the DC component of a supply voltage, the N7020A probe presents a high
impedance and thus low loading (about 50 kΩ). To the AC component of the
supply voltage, the probe presents a low 50Ω impedance. This probe's low input
impedance, reduces noise on the probe's output to the oscilloscope thus
increasing measurement range and accuracy.
The following graph shows the probe's input impedance versus frequency.
Figure 6
Minimize Probe Ground Impedance for the Best Signal Fidelity
The N7020A is a single-ended probe that is designed for measuring small signals
riding on large DC voltages. By using the oscilloscope's offset knob to offset the
DC voltage, you can analyze a power rail using maximum vertical sensitivity. With
no added noise other than a 10% increase to the oscilloscope channel's noise, due
to 1.1:1 attenuation, the N7020A has very low input noise. For example, at
maximum sensitivity on an S-series oscilloscope, the input-referred AC
140 µV
N7020A User's Guide
Input Impedance Versus Frequency,
(N7020A with N7022A Main Cable)
.
rms
Using the N7020A
Z
Measured,
Z
Modeled
in
in
2
noise is
rms
25
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