lämmitysjännitteen

Lämmitinjännite, sometimes referred to as filament voltage, is the voltage applied to the filament (or cathode) of certain vacuum tubes, most notably vacuum fluorescent displays (VFDs) and older cathode ray tubes (CRTs). The purpose of this voltage is to heat the filament to a temperature sufficient for thermionic emission. Thermionic emission is the process where electrons are released from a heated surface. In VFDs, these emitted electrons are then accelerated and strike a phosphor coating on the display, causing it to glow. In CRTs, the emitted electrons form a beam that is directed towards a phosphorescent screen.

The value of the lämmitysjännite varies depending on the specific tube or device. For VFDs, common filament voltages are typically in the range of 1 to 5 volts AC or DC. This low voltage is designed for energy efficiency and to ensure a long lifespan for the filament. In CRTs, filament voltages were generally higher, often around 6.3 volts. The power consumed by the filament is a significant factor in the overall power consumption of a vacuum tube device. Ensuring the correct lämmitysjännite is crucial for the proper operation and longevity of the vacuum tube. Too low a voltage will result in insufficient electron emission and a dim or non-existent display, while too high a voltage can overheat and rapidly degrade or destroy the filament.