On my vacuum tube computer that I'm building up, I run all my tubes at just 24V. Furthermore, my basic inverter design (which is the primary building block of the entire machine) is identical for all the different gates. I use a 33k plate resistor and tie the cathode directly to ground. So, this tester actually tests tubes in the same environment as the tube computer and dumps the results out through the serial monitor!

There's a Github link below to the source code used for the Arduino, and a schematic is included in the pictures.

Check out the full video here for more details: https://youtu.be/Yh8K46Id5sI