Key specifications
| Bandwidth | −3 dB roll-off point. Rule of thumb: BW ≥ 5 × signal bandwidth |
|---|---|
| Rise time | ≈ 0.35 / BW. A 100 MHz scope has ~3.5 ns rise time |
| Sample rate | ≥ 5× BW (typ. 10×) for proper single-shot capture |
| Memory depth | Record length / sample rate = capture window |
| Vertical resolution | 8-bit typical; some scopes 10 or 12-bit |
| Input impedance | 1 MΩ ∥ ~15 pF (passive), 50 Ω (RF mode) |
Probes
| Type | BW | Attenuation | Use |
|---|---|---|---|
| 10× passive | up to ~500 MHz | 10× | General — default |
| 1× passive | ~10 MHz | 1× | Low signal, low-BW |
| Active FET | 500 MHz – 2 GHz | Usually 10× | High BW, low capacitance |
| Differential | varies | varies | Differential pair, isolated mains |
| Current probe | Hall + toroid | — | Non-invasive current measurement |
Triggering
- Edge: most common — rising or falling at a threshold.
- Pulse width: trigger on pulses narrower/wider than set.
- Runt: trigger on partial-amplitude pulses.
- Slope: trigger on dV/dt faster/slower than set.
- Serial (I²C, SPI, CAN): trigger on protocol events.
- Video: trigger on frame / line sync.
Probe compensation
- A 10× passive probe has a compensation cap that must match the scope input capacitance — adjust until the calibration square wave shows flat tops.
- Under-compensated = rounded tops. Over-compensated = overshoot.
- Always check compensation when moving probes between channels/scopes.
Notes
- A 100 MHz scope will see a 100 MHz sine wave at −3 dB (~71% amplitude) — don't trust amplitudes beyond ~BW/5.
- Ground-lead length affects high-speed measurements — use the short spring clip, not the alligator ground.
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