What does a tube tester do?

A tube tester provides mechanical and electronic interface for vacuum tubes and an operating environment. Power supplies are provided including filament power for the heater, plate voltage, bias and screen voltage. These voltages are maintained across a tube type as a “test regime” so that the performance of a given tube can be compared against all others of its type. All tube testers create unique test settings for a given tube type, and therefore test results between testers are rarely the same, though they are often proportional and can be correlated.