When the lamp is turned on current passed through the starting electrode and jumps the short distance to the main electrode see the diagram below , this is aided by argon gas.
The argon gas strikes an arc at low temperatures. You can also see the 8 minute video on this page which includes animated graphics how it works. After the initial small arc the tube heats up and the mercury is vaporized.
Electric arcs fight to work through the resistance of a gas, but over time more molecules of the gas become ionized. This makes it even easier for more electric current to pass through, so the arc gets wider and hotter. In the lamp as the first arc heats up, it begins to turn the solid mercury into a vapor, soon the arc is able to travel through the mercury vapor to reach the other main electrode on the opposite side of the discharge tube. There is less resistance on this path now and current stops flowing through the starting electrode, just as a river changes course to a path of least resistance, drying out the previous channel.
After a mercury vapor arc strikes and heats, the halides vaporize and the halides dissociate. The metal atoms diffuse away from the arc to cooler areas and recombine with the halogen before they damage any part of the silica or electrodes.
The lamp is now fully warmed up and produces its white light. Metal halide work lamps are clearly visible in construction on the world trade center tower there are no walls to block work lights yet in this photo.
Construction Materials:. The high pressure and temperature of this light would normally react and destroy the silica in normal glass. Fused quartz is used due to a high melting temperature, and by using halogens the destructive process is stopped. Tungsten has the highest melting point of any metal and therefore it makes the best electrode material.
The tungsten is treated with radioactive thorium Thl4 ThO2. This helps increase the life of the tungsten and lamp itself. Metal halide is a favorite for sports field lighting. Borosilicate glass is used in the outer envelope bulb due to its ability to insulate as well as block UV-B radiation coming from the arc. The bulb also prevents users from touching and fouling the fused quartz discharge tube with oil from the skin.
The mercury vapor arc in the metal halide lamp produces UV light. Borosilicate glass, also known as Pyrex insulates the lamp, insulating the lamp is extremely important to keep the color constant. Some halides have a lower vaporization point and will begin to drop out of the discharge if the lamp gets colder. The halides are designed in a balance to create the desired white light, loss of the the Agl halide for example will make the lamp turn more blue.
Stabilizing the MH lamp arc and color was the main problem that Steinmetz wasn't equipped to solve in the first lamps of Molybdenum is used in the seal of the discharge tube because it does not expand or soften easy, even under extremely high temperatures.
Expansion of the electrode coming out of the discharge tube would crack or break the sealed tube which forms a flat seam on each end. Molybdenum is also highly resistant to corrosion and is also used in high strength steel, armor and electrical contacts.
Metal halide work lights on the Hudson River. You can clearly see the power of HID lamps here. Only spot and search lights are more powerful. Variations and Uses. The first MH lamps had a large outer envelope. In the last 20 years engineers have been able to make a smaller MH lamp at higher pressures. The higher pressure means a higher efficiency as well. Left: 1 cm diameter MH lamp used in a hand held flashlight.
Smaller sized bulbs with lower wattages have allowed for wider application of uses. It uses an igniter to create a high voltage pulse. This model has a shield to diffuse light and prevent damage to the lamp if the lamp explodes this can happen at the end of life.
The MH lamp has been used in Europe for automobile headlights for some time. It recently has recently become legal to use as an automotive headlight in the US. These lamps cast a cooler light with a poorer color rendering index than Halogen. Reiling demonstrated to the examiner that his lamp operated differently than Steinmetz's, and argued that the new lamp should receive a patent. Apparently the examiner was convinced, as U. In , Reiling donated his original patent document, the copy of Steinmetz's patent seen above, and one of the Steinmetz replicas to the National Museum of American History.
The replica is currently on display. The image above has been enhanced electronically. Chamraj Peth, Bengaluru Factory No. Anekal , Bengaluru O. Company Video. Comlur 2nd Stage, Bengaluru No. Kamakshipalya, Bengaluru Keerthikumar T. Road, Bengaluru - , Dist. Have a requirement? Get Best Price. View by: Product Supplier. Location Near Me. Popular Metal Halide Lamp Products. Janta Light House. Venture Lighting India Limited.
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