Automation Scripting

UART & CAT Commands

Usable Scripts

Remote Instrument Control (Rationale)

T&M automation involves using computers to remotely control instruments.
This allows measurements to be rapidly gathered and parameter sweeps to be easily automated by controlling multiple instruments.
Data acquired can also be analyzed to automatically determine if a design is meeting specifications or not, generating faults, etc.

Sweep the frequency of a function generator, observe the effect on the amplitude and phase of an output signal (Bode plot)
Sweep the input power applied to a PA, observe the output power / efficiency
Sweep VGS and VDS in a MOSFET, observe drain current (i.e. curve tracing)
Sweep message signal frequency in a modulated signal, observe frequency response of demodulator.

– USB

– Serial data transfer (RS-232)

– PCI Extensions for Instrumentation (PXI)

– Ethernet / LAN Extensions for Instrumentation (LXI)

VISA = Virtual Instrument Software Architecture
- Given the proliferation of physical interfaces (LXI, PXI, etc.) and protocols (TCP/IP, USBTMC, etc.) for communicating with instruments, it makes sense to have a standardize software interface to an instrument.
- VISA is an “industry standard” application layer interface (API) used by many T&M companies to allow instrument control via various languages (C, MATLAB, Python, etc.)
- VISA essentially allows us to issue commands to instruments through a common (virtual) interface.

Commands are often hierarchical, with subsystems expanding from a tree of the root command.
There are long- and short-forms of commands, e.g. "MEAS" and "MEASure" do the exact same thing.
Often, the same commands are using for setting and for querying:

– "VOLT 5" might set the output voltage to 5V

– "VOLT ?" queries what the output voltage is set to

PyVISA is a Python interface to VISA, allowing this powerful scripting language to control instruments.

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