The Mercury Vapor Lamp 1901

Summary

This script delves into the intricacies of mercury vapor lamps, highlighting their operation principles akin to metal halide lamps. It features the Philips-made Westinghouse Lifeguard lamp, renowned for its longevity and energy efficiency, despite its low color rendering index. The video explores different types, including the clear lamp with its blue-white light, the GE bonus line C lamp with improved color rendering due to phosphor coating, and the smaller wattage lamp with Yttrium Vanadate phosphor for a crisp, cool white light, suitable for both indoor and outdoor applications like streetlights.

Takeaways

• 🌟 The script discusses mercury vapor lamps, a type of light source that operates on the same principle as metal halide lamps.
• ⚡ The lamp functions by passing current through argon gas, heating mercury until it vaporizes and produces light through an arc stream.
• 💡 It doesn't require a phosphor coating to emit usable light, unlike some other types of lamps.
• 🏭 The mentioned model is a 175-watt clear lamp made by Philips, originally a Westinghouse Lifeguard lamp, known for its durability and longevity.
• 🔹 These lamps are energy efficient and known to last up to 50 years, showing their continued viability despite attempts to phase them out.
• 🌈 The light produced is a blue-white color with a color temperature of around 6800 Kelvin, but it has a poor color rendering index (CRI) of about 15.
• ⏱ Mercury vapor lamps take approximately 5 minutes to warm up and will not re-light immediately after being turned off; they need to cool down first.
• 🔌 The clear mercury vapor lamp showcases its operation with visible electrodes and a starting electrode for reduced voltage at startup.
• 🌕 The GE Bonus Line C lamp is an early phosphor-coated mercury lamp that uses a quartz arc tube to transmit UV radiation, which then strikes a phosphor to produce a yellowish-white light.
• 🏙 A later, smaller wattage lamp uses Yttrium Vanadate phosphor, a rare earth phosphor, which improves color and light output, making it suitable for both indoor and outdoor use.
• 💡 The smallest mercury vapor lamp made is 50 watts, which can run on either 40 or 50 watts depending on the ballast, and is often used in street lighting for its crisp-cool white color.

Q & A

What is the operating principle of a mercury vapor lamp?

The operating principle of a mercury vapor lamp is similar to that of a metal halide lamp. The current passes through the argon gas in the tube, heating the mercury until it vaporizes. The mercury vapor then enters the arc stream, and as the lamp warms up, the intensity of the arc increases, producing light.

What is special about the Westinghouse Lifeguard lamp mentioned in the script?

The Westinghouse Lifeguard lamp is considered one of the best mercury lamps ever made, known for its longevity, with some units lasting up to 50 years in service. It is a clear mercury vapor lamp made by Philips after they bought out Westinghouse.

What is the color temperature of the mercury vapor lamp described in the script?

The color temperature of the mercury vapor lamp mentioned in the script is around 6800 Kelvin, which produces a blueish-white light.

How does the color rendering index (CRI) of the mercury vapor lamp affect the appearance of colors?

The mercury vapor lamp has a CRI of about 15, which is not very good for color rendering. As a result, colors may appear unnatural, such as a hand looking green when placed under the lamp.

What are the warm-up and restrike characteristics of mercury vapor lamps?

Mercury vapor lamps take about 5 minutes to warm up when started from cold. If turned off while at full brightness, they will not re-light until they have cooled down for between 5 and 10 minutes.

How does the starting electrode function in a mercury vapor lamp?

The starting electrode in a mercury vapor lamp reduces the amount of voltage necessary to start the lamp. It is positioned close to the main electrode, allowing a small voltage to ionize the gas and start the arc. Once the lamp is running, the arc runs between the two main electrodes.

What is the difference between a clear mercury vapor lamp and a GE bonus line C lamp?

The GE bonus line C lamp, or color improved lamp, is an early phosphor-coated mercury lamp. It has a phosphor coating on the inside of the bulb that glows in an orangish color when struck by the ultraviolet radiation from the arc tube, combining with the blue glow of the mercury vapor to produce a yellowish-white light with better color rendering.

What material is the arc tube of the GE bonus line C lamp made of, and why is it significant?

The arc tube of the GE bonus line C lamp is made of quartz, which is significant because quartz readily transmits ultraviolet light and does not block it, allowing the phosphor coating to glow effectively.

What is the smallest wattage mercury vapor lamp mentioned in the script, and what is its phosphor type?

The smallest wattage mercury vapor lamp mentioned is a 50-watt lamp with a Yttrium Vanadate phosphor, which is a type of rare earth phosphor that improves both the color and light output of the lamp.

How does the Yttrium Vanadate phosphor in the 50-watt mercury vapor lamp affect its light output and color?

The Yttrium Vanadate phosphor increases the light output by about 15% compared to an equivalent clear lamp and provides a crisp-cool white color with better color rendering, making it suitable for both indoor and outdoor use.

What is the significance of the high pressure sodium lamps in the context of mercury vapor lamps?

High pressure sodium lamps are mentioned as an alternative to mercury vapor lamps for street lighting. They have a similar initial warm-up time but can restrike within a minute after the power comes back on, unlike mercury vapor lamps that require cooling down.