If you're involved with servicing or building power supplies, you'll wonder how you ever managed without this ultra-useful testbench tool! This electronic load enables you to observe DC power circuits under a variety of load conditions, all of which can be quickly "dialled-in" using a single potentiometer.

An electronic load is good for testing batteries too. But why use an electronic load instead of a resistive load? Let's find out.

Resistance is futile

Electronic loads are often called "dummy" loads. This name refers to the fact that they replace or simulate a real load. For example, a dummy load might be used at the output terminals of a DC power supply to allow measurement of ripple voltage at different current levels. The dummy load enables us to conveniently program any load resistance (and thus current flow) that we desire.

Of course, a dummy load need not be electronic - it could consist of a rheostat or even a bunch of high-power resistors in series and/or parallel. However, these methods tend to be rather inflexible and lack adjustment range and resolution.

Rather than providing a variable load resistance, the electronic version presented here provides variable current sinking. This means that regardless of the applied voltage, the current that it "swallows" remains exactly as set. The required load current is simply "dialled in" via a multi-turn potentiometer, up to a maximum of 10A.

Note that, to handle both low and high-power circuits, we've included 1A and 10A switch-selectable current ranges.