One power supply can go up to 30 volts or 1 amp, and the other can go up to 18 volts or 3 amps: https://www.amazon.com/Extech-Power...?s=industrial&ie=UTF8&qid=1310083681&sr=1-26" https://www.amazon.com/Extech-Power...?s=industrial&ie=UTF8&qid=1310083681&sr=1-25" Why does one output higher voltage or lower current and the other output lower voltage or higher current? Since V = IR I would think the one that could put out a higher voltage on voltage mode would be able to put out a higher current on current mode (since voltage and current are proportional)... PS Maybe I misunderstand how these power supplies work and my physics understanding is fine. The way I understand these power supplies to work is that one either picks voltage or current mode. In voltage mode it simply outputs the voltage you ask for. In current mode it senses the current with the given resistance and increases or decreases the voltage to achieve the current you asked for. If my understanding of the power supplies is wrong (rather than my understanding of the physics) then please correct me. Thanks!