Connecting to Instruments

Connecting to Instruments

PyTestLab provides a unified and straightforward way to connect to both real and simulated instruments.

Using AutoInstrument

The pytestlab.AutoInstrument factory is the primary way to create a single instrument instance. You need to provide a configuration source, which can be a profile key (e.g., "keysight/DSOX1204G") or a path to a YAML file.

Connection Process

Creating an instrument instance with AutoInstrument.from_config() does not establish the connection. You must always call the connect_backend() method on the created instrument object.

Connecting to a Real Instrument

To connect to a physical instrument, you typically need its VISA address.

import pytestlab

def main():
    # Create an instrument instance from a profile and specify its address
    dmm = pytestlab.AutoInstrument.from_config(
        "keysight/34470A",
        address_override="USB0::0x0957::0x1B07::MY56430012::INSTR"
    )

    # Establish the connection
    dmm.connect_backend()

    print(f"Connected to: {dmm.id()}")

    # ... perform operations ...

    dmm.close()

main()

Connecting to a Simulated Instrument

To create a simulated instrument for development or testing, set the simulate=True flag. No address is needed.

import pytestlab

def main():
    scope_sim = pytestlab.AutoInstrument.from_config("keysight/DSOX1204G", simulate=True)
    scope_sim.connect_backend()

    print(f"Connected to simulated instrument: {scope_sim.id()}")

    scope_sim.close()

main()

Simulation mode is ideal for development, CI, and testing when hardware is unavailable.

Using a Bench

For managing multiple instruments, the pytestlab.Bench class is the recommended approach. It handles the connection and cleanup for all instruments defined in your bench.yaml file automatically.

import pytestlab

def main():
    with pytestlab.Bench.open("bench.yaml") as bench:
        print(f"Bench loaded: {bench.config.bench_name}")
        # Access instruments by alias, e.g.:
        bench.psu.channel(1).set(voltage=3.3, current_limit=0.5).on()
        voltage = bench.dmm.measure_voltage_dc()
        print(f"Measured: {voltage.values:.4f} V")
    # All instruments are closed automatically here

main()

See the Working with Benches guide for more details.

Troubleshooting Connections

  • VISA Not Found: Ensure you have installed a VISA library (NI-VISA, Keysight IO Libraries, etc.) and that it is accessible in your system's PATH.
  • Address Errors: Double-check your instrument's VISA address. Use pytestlab profile list and pytestlab bench ls to inspect available profiles and bench configurations.
  • Simulation: If you encounter persistent connection issues, try running in simulation mode to isolate hardware vs. software problems.

Next Steps

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