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S-2 Sunlight Mercury Discharge |
The S-1 was a large 400W source for general irradiation in public areas, and a smaller domestic source was soon in demand for residential use. Thus in 1937, this 130W S-2 variant was launched. Initially it had a clear glass bulb, but owing to its uses at short ranges its high brightness produced too much glare. From 1939 onwards both this and the larger S-1 were only made with inside frosted pearl bulb.
It is a most unusual kind of hybrid incandescent-discharge lamp. The bulb is is of a special UV-transmitting hard glass, and is filled with an enormous quantity of mercury plus low pressure argon. It contains a V-shaped tungsten filament, whose ends have extra windings to increase their thermal mass such that they can function as electrodes. When illuminated on a low voltage transformer, the filament lights and thermionic emission takes place. As the mercury begins to vaporise a glow discharge is formed, which gradually transforms into an arc across the ends of the filament, ballasted by the transformer. The filament continues to decrease in intensity as the arc draws more current, but remains lighted at all times. It produces a warm white light plus infrared radiation, while the mercury arc contributes ultraviolet rays. The lower power of this S-2 lamp required the addition of the metal cap, to raise the temperature of the mercury pool and increase the UV output.
| Manufacturer: | General Electric Co. of U.S.A. | |
| Lamp Power: | 130 Watts | |
| Lamp Current: | 8.5 Amps | 2A at starting |
| Lamp Voltage: | 15 Volts | 30V at starting |
| Cap: | E29s/30 | Admedium Brass |
| Bulb Finish: | Clear hard glass | Transmitting to 280nm |
| Bulb Type: | PS-54 | PS-17 (in eighths/inch) |
| Overall Length: | 122.5 mm | 4 7/8 inches |
| Light Centre Length: | 95.25 mm | 3 3/4 inches |
| Filament: | C-2V | Overwound plugged tails |
| Atmosphere: | Argon | 0.9 atm. during operation |
| Luminous Flux: | 1,600 lm | @ 100 hours |
| Luminous Efficacy: | 12.3 lm/W | @ 100 hours |
| Total Ultraviolet Output: | 8,000 E-Vitons | |
| Burning Position: | Vertical base up to horizontal | |
| Rated Life: | 300 hours | |
| Warm Up / Re-strike Time: | 8 minutes to full UV output | Instantaneous restrike |
| Factory: | Nela Park, Ohio | U.S.A. |
| Date of Manufacture: | December 1939 | |
| Original / Present Value: | Not Known | |