Keithley 228A Programmable Current Source

The Keithley 228A Programmable Current Source is a dual-function instrument capable of operating as either a constant voltage or constant current source with 100 W power capability. Four-quadrant operation enables sourcing and sinking across positive and negative polarities. Programmable control facilitates automated test sequences and calibration procedures, serving engineers, system integrators, and laboratory environments requiring precise output control and real-time monitoring.

– Technical Specifications

Output Ranges
• Voltage: 100 V, 10 V, 1 V
• Current: 10 A, 1 A, 100 mA (maximum 10 A)
• Power: 100 W source or sink

Output Characteristics
• Output inductance: 100 µH typical
• Output capacitance: 0.2 µF typical
• Transient recovery time (resistive load): ≤1 ms for 90% settling after load change
• Output load must be non-inductive

Output Resistance
• Current mode: 10⁴ Ω (10 A range), 10⁵ Ω (1 A range), 10⁶ Ω (100 mA range)
• Voltage mode: 100 mΩ (100 V range), 100 µΩ (10 V and 1 V ranges)

Sensing & Regulation
• Remote and local sensing via rear panel switch
• Remote sensing corrects up to 0.5 V per output lead (max 5 Ω per sense lead)
• Line regulation: <0.01% output change across AC line variations
• Warm-up time: 10 minutes to rated accuracy

Modulation Input
• Sensitivity: −10 V to +10 V varies output by ±100% full scale
• Accuracy: 2% typical, DC to 60 Hz
• Modulation bandwidth: 600 Hz
• Input resistance: 6.8 kΩ

Current Monitor Output
• Scale factor: 1 V = 100% of range
• Bandwidth: 5 kHz typical
• Output resistance: 10 kΩ

– Key Features

• Four-quadrant source/sink operation accommodates bidirectional testing
• Battery-backed program memory stores up to 100 test sequences
• Internal fan cooling with continuous temperature monitoring
• On-board self-test validates analog, digital circuits, and power supplies at startup
• Selectable remote sensing for lead drop compensation

– Typical Applications

Automated component characterization, precision calibration procedures, device burn-in, and parametric testing requiring synchronized voltage and current delivery with programmable control.