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Osram ME/D Compact Source Mercury |
The arc burns between electrodes of solid tungsten to provide a compact source of extremely high brightness. This, the simplest design of ME lamp, has the arc tube housed within a simple hard glass outer bulb and the cap is the standard 5-Amp plug, once the principal mains electricity socket in use in the UK. This very early lamp contains only an argon filling and has no starting electrode. Ignition was accomplished with the aid of a Tesla coil. The arc tube is hand-made throughout. Small cups of pressed nickel behind the electrodes prevent heat losses here and assist in raising the mercury vapour pressure.
ME/D lamps were once very popular high brightness light sources for monochrome slide and film projectors, film printers, and a great many still live on today in technical instruments such as projection microscopes and profile projectors. In addition to this glass design, a lamp having a pre-focussed base was also sold, and a number of types in metal boxes having quartz or glass windows were also made. The metal box types were sold for bare operation, the housing being capable of withstanding the blast should the arc tube explode at end of life. The glass types meanwhile are suitable only for enclosed operation. Today, for new applications they have been totally superseded by the double ended bare arc tube designs.
| Manufacturer: | The General Electric Company of England PLC | |
| Lamp Power: | 250 Watts | A.C. or D.C. supplies |
| Lamp Current: | 3.7 - 4.6 Amps | 4-5 Amp during starting |
| Lamp Voltage: | 60 - 70 Volts | Tesla coil for ignition |
| Cap: | 5-Amp Plug | Aluminium with brass pins |
| Bulb Finish: | Clear | Borosilicate |
| Bulb Type: | T-51 | |
| Overall Length: | 141 ± 3 mm (excl. pins) | |
| Light Centre Length: | 85 ± 3 mm (excl. pins) | |
| Electrodes: | Solid tungsten with sharpened tips, 3.75mm arc gap | |
| Inner / Outer Atmosphere: | Inner: Ar | Hg | Outer: Nitrogen |
| Luminous Flux: | Not published | |
| Brightness: | 20,000 stilb (1,300 MHCP) | |
| Colour Temperature & CRI: | CCT: | CRI: |
| Chromaticity Co-ordinates: | CCx: | CCy: |
| Burning Position: | Vertical cap down | |
| Rated Life: | 500 hours | |
| Warm Up / Re-strike Time: | 5 minutes | 15 minutes |
| Factory: | Wembley | United Kingdom |
| Date of Manufacture: | December 1959 | |
| Original / Present Value: | £15 10s 0d (1959) | £221.45 (2002) |
