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== Review == | == Review == | ||
These high pressure mercury vapour lamps are compact light sources that are viable for wide area lighting. Their average colour reproduction and large output means that they are better suited to outdoor lighting. Compared with flourescent lamps they were very compact, having better performance at low temperatures. A longer lifetime, that was around 10 to 15 times higher than tungsten lamps, meant that these lamps are well suited for use in places where lamp replacement was costly, as in high bay lighting and street lighting. They had similar useful life as fluorescent lamps. High pressure sodium lamps had higher light output, almost double, of mercury vapour lamps while having low quality colour reproduction. This means that mercury vapour lamps were still suited for areas where colour reproduction was moderately important and there was still an advantage from compact light sources, which means industrial and workshop lighting, sometime even commercial premises. | |||
Fixtures are generally compact, considering the light output made available, but are generally heavy due to the bulky electromagnetic gear being used. There are directional and omni-directional fixtures that are suited to various purposes. In street lighting, the well known cobra-head style lamppost was used, and they may still be available for purchase. They were only moderately effective as light covered a large area but a considerable amount of light was lost due to the fixture directing some of it upwards, with no control. Omni-directional fixtures were used in residential areas and parks, where ambience was more important than efficiency. Indoor fixtures were centered on the typical high-bay or low-bay purposes, having a metal parabolic reflector and directing most or the entire light output downwards. Other fixtures were compact, having a boxy design, with a symmetrical or asymmetrical lamp placement that was suited for flood lighting. These type of lamps were used indoor as well as outdoor, for floodlighting. There were no home designed fixtures as these lamps were not popular in home environments and were mostly used as porch lighting with a fixture design similar to street or area lighting. | |||
Nowadays, mercury vapour lamps are very well suited for outdoor lighting. As the number of available fixtures diminishes and only second-hand or used products are available, they may not be economically effective to purchase except when you can readily use them rather than collect them. Free standing lamps are quite capable on their own so if you need a compact light source that is highly durable and colour output is appreciated as is, then high pressure mercury vapour lamps are well suited. They are especially well suited for lighting in areas that are undergoing renewal work, workshops, gardens. Of special interest is renewals, since no modern LED lamp can output the same light spectra that dulls old painted areas and brightens newly painted ones. | |||
Operation | |||
These lamps are not well suited for frequent switching. They need a couple of minutes to reach maximum light output and they require a couple of minutes to restart after being turned off. The light colour and output changes from start-up to normal operation from a pink to white. A good lamp should have a strong pink light at startup, suggesting good internal coating performance. As the lamp ages, the coating degrades and light turns greenish. | |||
The lamp requires a conventional or electro-magnetic gear of the same power output as the lamp, connected in series with a lamp. Connecting the lamp directly to mains damages it instantly as there is no current limitation. A power factor capacitor that has a specific value might be used to correct the power factor and current requirements on the circuit. The lamp itself is not influence by the presence or absence of this capacitor. When used sparingly in homes or some premises where not a lot of these lamps are located, power factor correction is not important but large industrial or commercial clients were required to maintain a specific power factor due to electricity distribution contracting. | |||
Suitability | |||
The best lamps in terms of useful lifetime, colour reproduction, light output, are the equivalent OSRAM HQL branded lamps, not Philips HPL-N lamps even if Philips lamps were very popular. Chinese branded lamps are much worse in all performance and quality metrics with a greener light output and poor reproduction of oranges and reds. Reflector lamps are generally less versatile than the classic one for most purposes but they do not require any fixtures in most instances. | |||
The best choice of wattage are the 125 and 250 watt lamps as lower wattages have quite a low light output and larger powered lamps are bulky and too powerful for most purposes. The above lamp wattages are also cheaper as they were highly popular. Electro-magnetic ballasts or conventional gears are plentiful and can be used interchangeably with all manufactured lamps for a specific wattage. Lower rated power output gears can be used, making the lamp operate dimly but higher powered ones damage the lamp due to overstressing and are dangerous. | |||
Used lamp gears might work but old lamps are not as desirable. Rusted ballast may still operate but are a potential hazard while old, used lamps, may not have much useful life left and they may already exhibit some colour light emission issues. New old-stock lamps are the best choice, if available. | |||
== History == | |||
HPL-N lamps are high pressure mercury vapour lamps that have been produced, with somewhat similar properties, since the 1950s. The lamp's fluorescent coating technology dates back to around the end of 1930s while modern lamps were essentially manufactured as early as 1970s and are a result of subsequent improvements up until that time. The market for these lamps grew as industry and commercial activity recovered after the Second World War, meaning that research was justified by large sales. The energy crisis meant that clients demanded improvements and they were focused on improving these lamps, giving rise to derivatives such as metal-hallide lamps, with much better colour reproduction and lower energy consumption. Sodium lamps were improved, culminating in the high-pressure sodium lamps that, with their yellow-orange or golden glow, dominated exterior lighting. By late 1980s mercury vapour lamps where on a market share decline that laster | |||
These lamps were not intended for home or office use and they were seldomly used as such. Tungsten lamps had perfect colour reproduction and electric energy costs were very low. Even after the oil crisis of the early 1970s, tungsten lamps were still cheap enough and convenient to be used for general lighting. Also, these lamps did no require any gear. As mercury vapour lamps were heavily used in street lighting and industry. This means that development focused on colour reproduction but energy efficiency and reliability increases were most successful. | |||
In the p | |||
A midrange, quite slim, business laptop, released in 1998. It had an average mix of parts. Perhaps the single biggest issue is that the whole Dell CP and CPi range is very complex and difficult to understand. Differences between CP and CPi models is minimal in terms of aesthetics while most configuration options are difficult to spot. The major performance jumps are shown in the CPi lineup that has a Pentium II CPU model with major performance improvements, although the Pentium I option is still decent. The graphics chipset is quite fast, actually the best among Pentium I laptops, with good Windows acceleration and compatibility. Another rare feature is the presence of USB ports on a Pentium I era laptop, which is very nice and useful. | A midrange, quite slim, business laptop, released in 1998. It had an average mix of parts. Perhaps the single biggest issue is that the whole Dell CP and CPi range is very complex and difficult to understand. Differences between CP and CPi models is minimal in terms of aesthetics while most configuration options are difficult to spot. The major performance jumps are shown in the CPi lineup that has a Pentium II CPU model with major performance improvements, although the Pentium I option is still decent. The graphics chipset is quite fast, actually the best among Pentium I laptops, with good Windows acceleration and compatibility. Another rare feature is the presence of USB ports on a Pentium I era laptop, which is very nice and useful. | ||