Controlling the VNA Using Python and IVI-COM

Summary

Some applications require the use of IVI-COM to control hardware so that the software SFP does not need to be running in the background.

IVI-COM is the Component Object Model library, maintained by the IVI foundation. Instead of controlling the instrument purely through SCPI commands, IVI-COM behaves more like objects in a .NET environment where dot syntax is used to "navigate" to the desired member function or variable in a hierarchical path.

This solution uses Python and a third-party Python library called Comtypes (see the Comtypes documentation here).

Prerequisites

This example was tested working in Python 3.9.6 64-bit and Comtypes library version 1.1.11, 1.1.14 (Comtypes homepage).

IVI drivers are also required, which come with Keysight's IO Libraries. This example uses version 18.2.28014.7.

Installing Comtypes requires pip, which is often installed alongside Python itself. If pip is not installed on your system, see installing pip.

Note: Install the Comtypes library by opening a command prompt and execute:

             py -m pip install comtypes

For this example to work with your instrument, you must first change the string variable "VISA_ADDRESS" to match the connection string which refers to your VNA. You can find this string in Keysight Connection Expert:

Any of these three VISA Addresses should work, but the last one is recommended as it is the most human-readable.

Note: If your instrument uses more than one module for the same unit, such as with the P5028A, add both connection strings from Connection Expert to the VISA_ADDRESS string, separated by a semicolon (;).

An example of this is shown in the code block below.

Example