# Electronic – What’s a safe method for determining the switching frequency of a blackbox ACDC converter

safetyswitch-mode-power-supply

My project uses an off-the-shelf ACDC converter that conceals design details from such as switching frequency (or SF range). It's 24 V output rated to 5 Amps. I want to measure it's switching frequency but was advised against probing the device with an oscilloscope since it can be dangerous. Any advice how I can accomplish this safely?

#### Best Answer

simulate this circuit – Schematic created using CircuitLab

This is one way; with a load on the dc power supply output you can examine the ac ripple on a scope. Use a high-pass filter (HPF) that presents a load of 50 to 100 $$\\Omega\$$ (as shown in the schematic) with a 1:1 oscilloscope probe. You should expect to see 50mV or so.