Current Control
The CS Series uses true current feedback control. This is considerably different from many commonly available AC power sources that use a voltage feedback scheme in combination with a constant current mode of operation. Such power sources adjust the output voltage to try and maintain the requested current level (Voltage controlled current). These voltage controlled current sources have a finite response time to sudden impedance changes, which typically results in dynamic current over or undershoot as the load impedance changes. A current controlled current source does not suffer from the response lag and will always maintain the current at the specified level, regardless of transient load conditions. The maximum compliance voltage supported by the CS Series is 135 Vrms. A lower compliance voltage trip level can be programmed as needed.

Waveform Generation
The CS Series provides sine, clipped sine and square waveforms in addition to user defined arbitrary waveforms. Harmonic waveforms can be used to test for harmonic current susceptibility of a unit under test. With the help of the supplied Windows Instrument Control Software (ICS), defining harmonic waveforms is as easy as specifying the relative amplitude and phase angle for each of up to 50 harmonics. The user also has the ability to define arbitrary waveform data. Complex AC current anomalies can be simulated this way. The waveform data points generated are downloaded by the ICS to the AC source through IEEE-488, USB or RS232C bus. Up to 50 user-defined waveforms can be stored and given a descriptive name for easy recall. Downloaded waveforms are retained in non-volatile memory for recall over the bus or from the front panel.

Transient Generation
To simulate complex current events, the CS Series offers a list of transient steps. These steps can be programmed from the front panel or downloaded over the interface using the software supplied. The ICS allows libraries of commonly used sequences to be created on disk for quick recall. Once downloaded, the transient program can be executed from the PC or from the front panel. AC current transient generation allows the effect of rapid changes in current, frequency and current waveform shape on the unit under test to be analyzed. The combination of transients and user defined arbitrary waveforms creates a powerful test platform for AC powered products.

Measurements
The CS Series measurement system is based on real-time digitization of the voltage and current waveforms using a 4K-sample buffer. The digitized waveform data is processed by a Digital Signal Processor to extract conventional load values such as rms voltage, rms current, real and apparent power. The same data is also used to perform Fast Fourier Transformation (FFT) to extract the harmonic amplitude and phase angle of 50 harmonics.

Standard Measurements
The following standard measurements are available from the front panel or via the bus: Frequency, Phase, Voltage (rms), Current (rms), Peak Voltage, Voltage Crest Factor, Real Power, Apparent Power, Power Factor

Advanced Measurement Functions
In addition to standard load parameters, the CS Series is capable of measuring voltage and current amplitude and phase harmonics. Total harmonic distortion of both voltage and current is also available. Advanced measurement results like harmonic content of voltage and current for all three phases are available over the bus. The ICS can be used to save and print harmonics data in tabular, bar graph or time domain formats. The acquired voltage and current time-domain waveforms for each output phase can also be displayed using the software. Waveform displays on the PC include voltage and current combined, three-phase voltage, three-phase current and true power. The time-domain data is also available for transfer to a PC.

Windows Graphical User Interface
The Instrument Control Software (ICS) offers a soft front panel interface for operation from a PC running Windows Vista™, Windows XP™, or Windows 2000™. The following functions are available through this software:

• Steady state output control (all parameters).
• Create, run, save and print transient programs.
• Generate and save harmonic waveforms.
• Generate and save arbitrary waveforms.
• Measure and log standard measurements.
• Capture and display Voltage and Current waveforms.
• Measure, display, print and log harmonic voltage and
• current measurements.