FNIRSI DPOF1204 4CH | Power Ripple Looks Clean at 20MHz?

[00:00:00]Today, we'll measure power supply ripple and show why the 20 MHz actually matters. Safety first, only measure isolated low voltage DC rails with a standard probe. [music] For non-isolated or mains referenced circuits, use a differential or isolated probe. Here, DPOF1204, ground [music] spring probe, bench supply, e-load, and optionally two caps for standard ripple [music] testing.

[00:00:23]We'll measure ripple right at the output capacitor or output terminals while the electronic load applies a controlled [music] current. Set your voltage and current limit on the supply and keep the output off while you wire up. On the electronic load, choose constant current mode, set an initial current, and keep the load off until everything is connected. Wire the supply to the load with short, thick leads [music] and double-check polarity before turning anything on. For ripple, avoid the long ground clip. Use a ground spring or the shortest possible ground. This minimizes loop area and prevents false high-frequency noise. Connect the probe tip to the rail and the ground spring [music] to ground. Keep the loop extremely small. Now, set up CH1.

[00:01:02]Correct probe ratio, choose AC coupling for ripple, and we'll [music] start with full bandwidth. Switch to AC coupling to remove the DC level and focus on the ripple. Set a sensitive vertical scale, typically tens of millivolts per division, [music] and center the trace without clipping. Choose a time base that matches your target, milliseconds for switching ripple, microseconds for spikes. [music] Set an edge trigger on CH1 with AC coupling. A trigger level near 0 V usually gives a stable display.

[00:01:31]>> [music] >> Add measurements like VPP and VRMs to quantify ripple. Keep the readouts visible on screen. Turn the supply on, then enable the load. Let the current stabilize before taking readings. First, capture ripple at full bandwidth. Note the waveform and the VPP or VRMs readings. Now, enable the 20 MHz [music] bandwidth limit on CH1 to reduce high-frequency noise. You'll [music] see the channel tag change to 20M and the trace becomes cleaner. This is the standard approach for many ripple measurements. Compare them side by side, full bandwidth often shows extra high frequency [music] content while 20 MHz limit focuses on ripple within 20 MHz.

[00:02:11]Ripple changes with load, increase current step by step and record VPP at each load point. [music] For fast spikes, zoom the time base in.

[00:02:23]Remember, 20 MHz limiting will attenuate components above 20 MHz. So, use full bandwidth when you specifically need to study high frequency spikes.

[00:02:33]Save a screenshot or waveform file so you can document ripple at each test condition. [music] To get reliable ripple results, use a short ground, AC [music] coupling, and the 20 MHz limit when required, then document your readings. [music] That's the workflow on the DPOF1204.