Introduction: The Power of Programmable Control in Modern Engineering

In today's fast-paced electrical engineering landscape, manual instrument operation is often a bottleneck. The demand for efficiency, repeatability, and precision in testing and development cycles necessitates automated control. For DC power supplies—critical components in virtually every electronic system—this automation is primarily achieved through Standard Commands for Programmable Instruments (SCPI).

At AFB Power, we understand the critical need for seamless integration and remote control of our variable and 800V programmable DC power supplies. This guide is designed for engineers and purchasing managers seeking to leverage the full potential of SCPI commands, transforming tedious manual adjustments into streamlined, automated processes.

Understanding SCPI: The Language of Instrument Automation

SCPI (pronounced "skippy") is an ASCII-based command language designed to control programmable test and measurement instruments. It provides a standardized, hierarchical structure for communicating with devices, ensuring interoperability across various manufacturers and instrument types. This standardization is crucial for developing robust automated test equipment (ATE) systems.

The foundation of SCPI lies in the IEEE Std 488.2 standard, which defines the common command syntax and data exchange rules. Building upon this, SCPI extends the command set to address specific instrument functionalities, such as setting voltage, current, or reading measurement values on a DC power supply. You can explore the foundational principles further at https://standards.ieee.org/ieee/488.2/718/.

SCPI commands typically follow a tree-like structure, allowing for precise control over specific instrument functions. For example, SOURce:VOLTage:LEVel:IMMediate:AMPLitude 10V is a full command to set the immediate voltage level of the source to 10 volts. Most instruments allow for shorthand versions, like SOUR:VOLT 10. This hierarchical approach makes commands intuitive and easy to understand once the basic structure is learned.

Communication with SCPI-enabled instruments typically occurs over standard interfaces such as GPIB (IEEE-488), USB, or Ethernet/LAN (using protocols like VXI-11 or LXI). Before sending SCPI commands, a communication channel must be established using a suitable driver library, such as VISA (Virtual Instrument Software Architecture).

Establishing Communication and Basic DC Power Supply Control

Before sending SCPI commands, you need to establish a physical connection and set up your software environment.

1. Physical Connection:

USB: Connect the power supply to your PC via a USB cable. Drivers may be required.

LAN/Ethernet: Connect the power supply to your network. The instrument will typically acquire an IP address (static or DHCP).

GPIB: Connect using a GPIB interface card in your PC.

2. Software Environment: Most programming languages can interact with SCPI instruments through VISA libraries. Python with the PyVISA package is a popular choice due to its simplicity and extensive community support. Other options include MATLAB, LabVIEW, C#, or custom C++ applications.

Example: Connecting and Basic Control (Python with PyVISA)

First, ensure you have pyvisa installed (pip install pyvisa).

``python import pyvisa

`Create a resource manager instance`


rm = pyvisa.ResourceManager()
List available resources (optional, for debugging)
print(rm.list_resources())
Open a connection to your AFB Power supply
Replace with your instrument's actual address:
For USB: 'USB0::0xXXXX::0xXXXX::XXXXXXXXXX::INSTR' (Vendor ID, Product ID, Serial Number)
For LAN: 'TCPIP::192.168.1.100::INSTR' (replace with your instrument's IP address)
For GPIB: 'GPIB0::X::INSTR' (replace X with the GPIB primary address)
try:
    instrument = rm.open_resource('TCPIP::192.168.1.100::INSTR')
    instrument.timeout = 5000  # Set a timeout for operations (in milliseconds)
    instrument.write_termination = '\n' # Ensure correct line ending
    instrument.read_termination = '\n'
    print("Connected to:", instrument.query('*IDN?')) # Query Identification string
    # --- Basic DC Power Supply Commands ---
    # Reset the instrument to its default state
    instrument.write('*RST')
    print("Instrument reset.")
    # Set Output Voltage (e.g., 12.5 Volts)
    instrument.write('SOURce:VOLTage 12.5')
    print("Voltage set to 12.5V.")
    # Set Output Current Limit (e.g., 2.0 Amperes)
    instrument.write('SOURce:CURRent 2.0')
    print("Current limit set to 2.0A.")
    # Enable the output
    instrument.write('OUTPut:STATe ON')
    print("Output ON.")
    # Wait for a moment (simulate operation)
    import time
    time.sleep(2)
    # Query actual output voltage and current
    actual_voltage = instrument.query('MEASure:VOLTage?')
    actual_current = instrument.query('MEASure:CURRent?')
    print(f"Measured Voltage: {float(actual_voltage):.2f}V")
    print(f"Measured Current: {float(actual_current):.3f}A")
    # Disable the output
    instrument.write('OUTPut:STATe OFF')
    print("Output OFF.")
    # Clear all status registers
    instrument.write('*CLS')

except pyvisa.errors.VisaIOError as e: print(f"Error connecting or communicating with instrument: {e}") finally: if 'instrument' in locals() and instrument: instrument.close() print("Connection closed.")`

Safety Considerations: When working with high-power DC supplies, especially AFB Power's 800V units, always adhere to strict safety protocols. Current Limits: Always set appropriate current limits (SOURce:CURRent) before* enabling the output (OUTPut:STATe ON`) to protect your Device Under Test (DUT) and the power supply.

Wiring: Ensure correct and secure wiring, especially for high voltages and currents.

Remote Sensing: Utilize remote sensing if available to compensate for voltage drops in load leads, ensuring accurate voltage delivery at the DUT.

Advanced Control and Application Use Cases with AFB Power Supplies

AFB Power's variable and 800V programmable DC power supplies are engineered for demanding applications, and SCPI control unlocks their full potential for advanced testing scenarios.

1. Programmable Ramping and Sequencing: Many AFB Power units support advanced features like voltage and current ramping. Instead of