Capturing In-Rush Current Using a Digital Multimedia

This demonstration, led by Seok Jin, Product Manager for Digital Multimeters at Keysight, showcases the process of capturing the in-rush current of a DC-to-DC converter using the digitizer function of the Keysight Smart Bench Essentials Plus (SBE+) Truevolt Digital Multimeter (DMM). The video, approximately four minutes in duration, provides a step-by-step guide to setting up and executing the test, emphasizing the importance of in-rush current characterization in electronic design and validation.

In-rush current refers to the initial surge of current that occurs when power is first applied to a device, particularly those with significant input capacitance, such as DC-to-DC converters. Characterizing this current is crucial for three primary reasons: enhancing circuit protection, improving system stability, and ensuring the longevity of protection components like fuses and circuit breakers.

The demonstration begins with an overview of the test setup, which includes:

• A DC-to-DC converter (30V to 12V)
• The Keysight E36234A DC Power Supply to provide a 30V, 2A input
• The EL34243A Electronic Load to draw a constant 1A from the converter’s output
• And the DM34461A Truevolt DMM, which captures the in-rush current using its high-speed digitizing capability at 50,000 samples per second.
• The setup process is clearly illustrated with visuals and includes configuring the power supply, electronic load, and DMM. The DMM is set to DC current (DCI) mode with digitizing enabled. A trigger level of 7 milliamps is used to detect the rising edge of the in-rush current pulse, ensuring consistent and accurate capture of transient events.

Once the instruments are configured, the test sequence involves activating the electronic load, initiating the DMM’s digitizing function, and finally powering on the DC supply. The DMM immediately displays the captured in-rush current waveform, which can be zoomed and analyzed in detail. The demonstration highlights how different zoom levels (50%, 200%, 1000%) help in identifying the peak overshoot and settling behavior of the current.

The key takeaway is the ability of the SBE+ Truevolt DMM to effectively capture and visualize fast transient signals. With its 6.5-digit resolution, 7-inch display, and high sampling rate, the DMM is well-suited for analyzing low-level current signals, down to the microamp and picoamp range. This makes it an invaluable tool for engineers working on power electronics, particularly in evaluating the robustness and reliability of DC-to-DC converters during power-up conditions.

In conclusion, this demonstration underscores the ease and precision with which Keysight’s SBE+ Truevolt DMM can be used to characterize in-rush current, aiding in better design decisions and improved device reliability.