Aula 13 EAD II MSO/ DHO Curve Tracer Parte 1

Summary

This lesson introduces new functionalities of oscilloscopes, particularly the MSO and DSO series, focusing on performing 'cold tests' without powering the board. Typically, oscilloscopes perform 'hot tests' where the board is powered. However, by using a custom-built curve tracer hardware, users can perform cold tests, mapping voltage and current waveforms of components like semiconductors, resistors, and capacitors. The XY mode of the oscilloscope enables testing and comparing component characteristics, offering more detailed insights than a multimeter. The video demonstrates the setup process, calibration, and practical examples of testing PCBs and individual components.

Takeaways

• 🧑‍🏫 The class will focus on new features of oscilloscopes in MSO and DHO series, especially for cold testing of boards without powering them.
• ⚡ Typically, an oscilloscope performs hot tests, where the board needs to be powered and consuming current, but the lesson will show how to perform cold tests using a curve tracer.
• 📉 The curve tracer works with the oscilloscope's XY mode (voltage and current) to test components without powering the board.
• 🔋 Cold tests plot voltage-current characteristics of components like semiconductors, resistors, and capacitors, generating characteristic curves.
• 📊 These curves serve as a 'fingerprint' for each component, useful for testing components, their connections, and the board as a whole.
• 🖥️ The oscilloscope can store the plotted curves, allowing comparison between a faulty board and a reference board.
• 🔍 The curve tracer provides more detailed testing than a multimeter, especially for reactive components like capacitors and inductors.
• 💰 The components for building a curve tracer are relatively inexpensive (around $100), and the teacher provides additional materials for building one.
• 🛠️ The XY mode requires two probes connected to the oscilloscope, and adjustments are made to the time base and amplitude settings.
• 🔧 Once set up, the curve tracer can map component behaviors like diodes, resistors, and potentiometers, offering more precise diagnostics for PCBs.

Q & A

What is a 'cold test' in the context of using an oscilloscope?

A 'cold test' refers to testing a PCB (printed circuit board) without powering it, meaning the board doesn't need to be energized. This is different from the traditional 'hot test,' where the board must be powered and have current circulating.

What role does the curve tracer play in cold testing?

The curve tracer is an additional hardware that, when used with an oscilloscope, allows for cold testing of components and circuits. It helps plot the voltage and current characteristics of components like semiconductors, resistors, and capacitors, providing a 'fingerprint' curve for each component.

What is the 'XY mode' on an oscilloscope, and how is it used?

The XY mode is a function on oscilloscopes that allows plotting voltage on one axis and current on the other, rather than the usual time-based measurement. This mode is crucial for plotting the characteristic curves of electronic components during cold testing with a curve tracer.

Why is the XY mode better for testing components than the traditional diode testing mode on a multimeter?

Unlike the diode mode on a multimeter, which provides limited information, the XY mode combined with a curve tracer can plot detailed voltage-current relationships of components, including reactive ones like capacitors and inductors, offering a much clearer picture of their behavior.

What kind of waveforms or curves can be plotted using the curve tracer and oscilloscope?

The curve tracer and oscilloscope can plot curves for various components, such as diodes, resistors, capacitors, and even semiconductors. For example, a diode's characteristic curve or a resistor’s linear response can be visualized using this setup.

How can the curve tracer be useful in repairing faulty PCBs?

By comparing the curve plots of a faulty PCB to a known good one, the curve tracer can help identify issues with specific components or connections. This is particularly useful when diagnosing problems like faulty Face ID connections on mobile devices.

What voltage and current does the curve tracer inject during cold testing?

The curve tracer injects a small voltage and current, typically around 3V and 4mA, which is safe for the components and similar to the reverse voltage applied by multimeters in diode testing mode.

How can the curve tracer improve the testing of reactive components?

The curve tracer excels at testing reactive components like capacitors and inductors by plotting their characteristic curves. This provides more accurate information compared to traditional multimeters, which may not handle these components as well.

What is the advantage of saving waveform data from cold tests?

Saving waveform data allows technicians to create a library of characteristic curves for components and circuits. This makes it easier to compare and diagnose faults in future tests by referencing the saved data.

How does the curve tracer's accuracy compare to a multimeter in diode mode?

The curve tracer provides more detailed and accurate measurements than a multimeter in diode mode. It can test components with greater precision and is particularly effective at detecting overload conditions and measuring reactive components.