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Westinghouse 'CX' Mild Ultraviolet Incandescent |
Ordinary incandescent lamps deliver a continuous spectrum, the vast majority of which is radiated in the infrared spectrum. A small quantity is of course also emitted in the visible wavelengths. The filament in fact produces about 1% ultraviolet radiation as well, but much of this is absorbed by the glass bulb. The CX lamps attempted to remedy that shortcoming by making the bulb from a special glass having reduced concentration of the usual iron (III) oxide impurity, which is responsible for the slight greenish hue of ordinary soda-lime silicate glasses and their consequently poor UV transmission. As such this lamp radiates a full spectrum right down to just under 300nm.
The filament runs slightly hotter than a normal incandescent lamp of the same power, so as to further increase the UV flux. It may seem unusual that it is not driven much harder still, but it must be remembered that the highest loaded "photoflood" style incandescent lamps were not introduced until 1932, rather later than the origin of this lamp. Their application also called for a relatively long lifetime.
CX lamps were often used for the treatment of skin conditions, where the small ultraviolet component was beneficial. They were produced in 60W A19, 250W G30 and 500W G40 ratings until the 1940s, but had been generally supserded even in the 1930s by more efficient ultraviolet mercury sunlight lamps like the S-1 and Ultra-Vitalux.
| Manufacturer: | Westinghouse | |
| Lamp Power: | 250 Watts | |
| Lamp Voltage: | 120 Volts | |
| Lamp Current: | 2.08 Amperes | |
| Cap Type: | E26s/25 | Brass & Vitrite |
| Bulb Type: | G-95 | G-30 in eighths/inch |
| Bulb Finish: | UV-transmitting | Inside Frosted |
| Filament Type: | C-7A/3s | Single Coil Wreath-Vee |
| Atmosphere: | Argon-Nitrogen | Red P getter |
| Luminous Flux: | 4075 Lumens | |
| Luminous Efficacy: | 16.3 Lumens per Watt | |
| UV-A Flux: | 0.3 Wrad | 320-400nm |
| UV-A Irradiance: | 30 mW/m² | @ 1 metre |
| Colour Temperature / CRI: | CCT: 2900K | Ra: 100 |
| Chromaticity Co-ordinates: | CCx: 0.445 | CCy: 0.407 |
| Lifetime: | Estimated ~500 hours | |
| Burning Position: | Universal | |
| Overall Length: | 152 mm | 6 inches |
| Light Centre Length: | 101 mm | 4 inches |
| Factory: | U.S.A. | |
| Date of Manufacture: | Approx. 1930 | |
| Original Value: | ||
