Oscilloscope

An oscilloscope uses a probe to connect to a test point in a circuit and amplifies or attenuates the voltage at that point. The signal path after that depends on the scope, but in general analog circuitry conditions the signal and an analog-to-digital converter digitizes it for further evaluation, processing, and analysis.

An oscilloscope captures and displays a signal in the time domain, while a spectrum analyzer captures and displays a signal in the frequency domain. Sometimes, an oscilloscope will have a spectrum analyzer feature built into it for the convenience of analyzing the signal in the time and frequency domains.

Passive probes: These are the most common types, suitable for low-frequency measurements. They only contain components like resistors and capacitors that passively respond to input signals, so they do not require external probe power.

Active probes: These are used for high-frequency measurements. They require external probe power for the active electronic components in the probe, such as amplifiers and transistors, which are used to improve signal fidelity and performance.

Differential probes: These consist of two sensing leads that measure the differential voltage between two test points where neither lead is grounded.

Current probes: These probes measure current waveforms. There are two types: clamp-on versions that do not break the circuit and types that you connect in series with the circuit.

For a complete selection guide on application-specific oscilloscope probes such as Hi-Z+ probes, high-frequency differential probes, power rail probes, and optical probes, you may refer to this Oscilloscope Probes Selection Guide.

Compatibility is not assured, even though many probes and oscilloscopes use standard connectors. It’s critical to verify:

• Bandwidth compatibility: The probe’s bandwidth should match or exceed the oscilloscope’s bandwidth.
• Connector type: Ensure the probe’s connector matches the oscilloscope input.
• Voltage and current ratings: Confirm the probe can handle the oscilloscope’s input range.

It would be best to refer to the specific oscilloscope and probe manuals for detailed operation and maintenance guidelines, which are crucial for effective and accurate measurements.

Automatic triggering, while convenient, may not always provide the level of precision engineers require. In contrast, normal triggering empowers engineers to specify the exact point at which they want to capture a waveform, offering a level of control and accuracy that can be crucial when troubleshooting problems. For instance, if you need to capture a specific pulse, normal triggering allows you to specify the precise time the pulse occurs. When you switch to the Single trigger mode, your oscilloscope will temporarily operate in normal trigger mode to prevent an automatic force trigger.

• In normal mode, the sweep starts only when the trigger settings are met. If the trigger is not met, the screen is not updated. This can be useful when capturing a transient event that may only happen once.
• In auto mode, the sweep is triggered automatically and continuously.
• In single mode, the sweep only occurs when the trigger is activated manually. This can be useful when you want to capture a particular single trigger event or signal condition.

Learn more about the applications and examples of when to use each mode from this deep dive lesson video.