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GE-Mazda Sunlight Mercury-Tungsten S-2 |
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. By 1932 this 130W S-2 variant had been launched. Initially it had a clear glass bulb, but owing to its use 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 made of a special hardglass transmitting UV down to 280nm, 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 causes a glow discharge to form. This quickly transitions into an arc across the ends of the filament, ballasted by the transformer. As the bulb temperature increases the mercury vapour pressure rises, and the arc gradually draws more current but the filament remains lighted at all times. It produces a neutral 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 UV output.
| Manufacturer: | General Electric Co. of U.S.A. | |
| Lamp Power: | 130 Watts | |
| Lamp Voltage: | 15 Volts | Approx. 30V at starting |
| Lamp Current: | 8.5 Amps | 2A at starting |
| Cap Type: | E29s/30 | Admedium Brass |
| Bulb Type: | PS-54 | PS-17 (in eighths/inch) |
| Bulb Finish: | Clear | #776 borosilicate glass |
| Electrodes: | C-2V filament | Overwound plugged tails |
| Atmosphere: | Hg | Ar | 0.9 atm. during operation |
| Luminous Flux: | 1,600 lm | @ 100 hours |
| Luminous Efficacy: | 12.3 lm/W | @ 100 hours |
| Radiant Flux: | UV-A 1.05W, UV-B 0.65W | Visible 8.4W |
| Colour Temperature & CRI: | CCT: 4050K | CRI: Ra67 |
| Chromaticity Co-ordinates: | CCx: 0.381 | CCy: 0.383 |
| Rated Life: | 300 hours | 50% survival, ~100% UV flux |
| Warm Up / Re-strike Time: | 8 minutes to full output | Instantaneous restrike |
| Burning Position: | Vertical base up to horizontal | |
| Overall Length: | 122.5 mm | 47/8 inches |
| Light Centre Length: | 95.25 mm | 33/4 inches |
| Factory: | NELA Park, Cleveland (OH) | U.S.A. |
| Date of Manufacture: | 1939 December | Date Code: 96.16 |
| Original Value: | US $3.75 (1939) | |
