Acquisition and waveform setup
R&S
®
RTO6
116
User Manual 1801.6687.02 ─ 05
An ideal probe fulfills the following requirements:
●
Safe and reliable contacts
●
Infinite bandwidth
●
The probe should not load the signal source and thus impact the circuit operation.
●
The connection should not introduce or suppress signal components (hum, noise,
filter) and thus degrade or distort the transferred signal.
In reality, the probe can never be an ideal one, it always affects the signal transmission
and the signal source, and thus the measured signal. It depends on the frequency to
be measured and on the signal source to determine the acceptable loading, and to
determine which kind of probe delivers good results.
The solution depends on the quantity to be measured regarding:
●
Signal type: voltage, current, power, pressure, optical, etc.
●
Signal amplitude: The oscilloscope itself can only display voltages in a limited
range. Most probes can adjust the dynamic range to amplitudes from a few mV to
10 V. Smaller or much larger signals require specialized equipment.
●
Signal frequency: High frequencies require advanced equipment to get correct
results.
●
Source characteristic: The source impedance is the decisive factor when choosing
the suitable connection.
5.1.4.1
Voltage probes
The following table provides an overview on common voltage probes and their usage.
Table 5-1: Voltage probes overview
Probe type
Attenuation
Typical bandwidth
range
Oscilloscope
input
Usage
Passive, high impe-
dance
1:1
10 MHz
1 M
Ω
Low-speed signals,
low-level signals
Passive, high impe-
dance
10:1
500 MHz
1 M
Ω
General purpose
Passive, low impe-
dance
10:1
up to 10 GHz
50
Ω
High frequency
Active, single-ended
10:1
up to 10 GHz
50
Ω
High speed
Active, differential
10:1
50
Ω
Floating
For a list of recommended probes, refer to the R&S
RTO6 product brochure.
Besides the possible input voltage range, two factors are important when selecting a
voltage probe: Bandwidth and impedance over frequency.
●
Bandwidth:
The combination of probe and oscilloscope builds up a system. The resulting sys-
tem bandwidth is approximately determined with:
Basics
