There are 5 main types of Lab power supplies: 1. Constant Voltage Supply: They are adjustable, they usually are supplied with a meter to show you the voltage the supply is set to. Some also have meters to let you monitor the current. 2. Constant Voltage/Constant Current Supply: In addition to supplying constant voltage type, these supplies can also supply constant current. When in constant current mode, the power supply will maintain the set current regardless of changes in the load's resistance. 3. Multiple Output Supply: Multiple output power supplies have more than one DC output, often two or three. These are useful and cost-effective for systems that require multiple voltages. An often-used power supply for circuit development is a triple output supply. 4. Programmable Supply: Programmable power supplies are sometimes called "system" power supplies, as they are often used as part of a computer-operated system for testing or production. 5. Multi-range Supply: Most conventional power supplies operate with fixed voltage and current ratings, e.g. 30V / 3A. Multi range supplies are different in that they recalculate voltage/current limits for each setting, forming a constant power hyperbolic shaped boundary. Any voltage/current combinations that lie on the hyperbolic curve are possible and in each case the supply operates at maximum power.