Microprocessor-controlled Vacuum Tube Analyzer
Here is a project I've been working on recently. It applies precisely-controlled voltages to the electrodes of a vacuum tube and measures the currents into the electrodes. Under software control, it can plot characteristics curves like those found in vacuum tube datasheets, as well as curves that the datasheets don't offer. The electronic circuitry is controlled by software running on a Raspberry Pi. You can attach a display directly to the Raspberry Pi, or you can run it remotely over the network as I did in this video. What you see here is just a prototype. It doesn't work perfectly yet, but it's already useful.