E1T Scaler Tube Built as Single Digit Clock

This single digit E1T clock was designed to be used for measurement equipment with high-speed counting.

A central position in the circuit is being taken by the E1T as the operating range of the tube is determined by the E1T tester. The clock achieves its goals by using an electron beam as opposed to a glow discharge that is used in the competing decatron. The use of a filament heated cathode implies this setup. All the parts in the circuitry carry a lethal voltage with respect to ground since the circuit is directly connected to the mains.

With an anode voltage as low as 200V and a filament voltage of 4 to 5V, the tube appeared to operate reliable. A lower pulse amplitude can be used with having lower anode voltage as long as the maximum counting speed is not required.

A stabilized anode voltage is needed for correct functioning of the E1T. This is done by designing the tubes in such a way that the voltage drop over the tubes remains more or less constant over a fairly large current range to maintain stabilization once the tube is ignited.

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