The 227 is a Current Source from Keithley. A current source is a type of electronic test equipment in circuit form that can deliver or absorb electrical current that’s independent of the voltage across its terminals. There are two types of current sources: dependent and independent. A dependent current source delivers an electric current that is proportional to another voltage in the circuit. An independent current source delivers a constant current.
The Keithley 227 Current Source is designed for high-performance applications requiring an accurate, stable, high-power constant current over full-scale ranges of 1 mA to 1 A with adjustable compliance voltage (3-300 V to 100 mA, 3-50 V to 1A). The true bipolar current output can be modulated, programmed, monitored, and even floated up to 500 V off ground. Excellent regulation, stability, and low noise assure high resolution and accurate output.