Every bench power supply datasheet lists a current limit, but how long does the supply actually take to act on it? When a load suddenly demands more current than the supply can deliver, there is a short window during which the output voltage sags before the constant-current loop (CC) pulls things back into line. The shape and duration of that sag is one of the more revealing things you can measure on a regulated supply, and it is also one of the easiest things to measure badly. This project is a small, deliberately simple tool that turns “suddenly connect a heavy load” into a clean, repeatable, single-button operation, so the transient response can be captured on an oscilloscope under identical conditions every time.

Why Not Just Use a Switch?

The obvious way to test current-limit behavior is to clip a load resistor across the supply and either flick a switch or short two probes together. In practice, this is precisely where the measurement falls apart. Mechanical switch conta...