Why do I get an exception in my test code when attempting to connect to my VNA?

One of the most common ways to connect to an instrument resource is using the VISA Open command, where you pass in the instrument resource string. Examples may be similar to the following:

C#

mbSession = (MessageBasedSession)rmSession.Open("TCPIP0::127.0.0.1::inst0::INSTR");

Python

myVNA = rm.open_resource("TCPIP0::127.0.0.1::inst0::INSTR")

One thing to keep in mind when working with the VNA is that the TVNA software must be running on the same PC where your program is executing. 

The other thing that is necessary is that you must ensure the VNA is connected to the PC. 

One way to quickly verify the connectivity of your setup (software & hardware) is to launch NI-VISA Interactive Communicator and verify that your instrument resource is available in the list of TCP/IP Instrument Resources:

If either the software is not running, the instrument is not connected, or the instrument was configured incorrectly, you will see the instrument resource listed with the the "Unknown" group with a yellow question mark next to it. 

You will be able to double-click on the resource and use the VISA Test Panel to send write and query commands to the instrument.

For examples on how to automate your Bird VNA visit the GitHub repository at: https://github.com/Bird-Technologies/Vector-Network-Analyzers