Gallery of Lights
Lamps => Modern => Topic started by: bryantm3 on July 15, 2012, 05:04:49 AM
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there are all sorts of these metal halide lights, and i don't know the difference between them— is the colour different or is it all in the mechanics of the thing?
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I'm not expert at the different types, but i'll try to explain the basic differences for you..
The traditional (probe start) metal halide is basically an improved MV lamp. It has an internal starting resistor liek MV lamps and doesn't require an ignitor. 175-1000W probe start MH ballasts will operate MV lamps of the same wattage without any modifications to the wiring. The color of probe start MH lamps tends to shift to a pink color over time and life is the shortest of all the lamps in the HID family at about 10,000 to 15,000 hours.
Pulse start metal halide (PSMH) is an improved probe start MH. The arc tube looks like a round ball for lower wattage lamps and more like a football with higher wattage lamps. The main differences between probe and pulse start MH is that PSMH uses an external ignitor like HPS lamps (so therefore PSMH lamps cycle at the end of their life like a HPS lamp). PSMH lamps also have a higher arc tube temperature. They also give more lumens per watt (so they're more efficient than probe start MH lamps) and last longer at about 20,000 hours on average.
Ceramic Metal Halide (CMH) is virtually the same concept as PSMH except unlike all other MH lamps, CMH uses a ceramic arc tube, hence the name ceramic metal halide. The Ceramic arc tube almost eliminates the possiblity of explosion and produces better quality light. Some CMH lamps such as the ones made by Philips can be used on magnetic core and coil ballasts, but most must operate on electronic ballasts. PSMH and CMH lamps can operate interchangably on PSMH ballasts most of the time (unless the lamp says it can only be used on electronic ballasts). Think of CMH lamps as a pulse start MH lamps with a ceramic arc tube instead of quartz. ;)
I hope this info helps as I don't know the major details of really any lamp, just the basics. :)
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streetlight98: There are some mistakes in your description about the different types of MH lamps:
1. Probe start metal halide: A metal halide lamp that have three electrodes in the arctube (Two main electrodes and one for starting), and a starting resistor. With the US ballasts, it can be operated without an ignitor, like a MV lamp. This is indeed correct that these are simply improved color MV lamps.
2. Pulse start metal halide: A metal halide lamp without a starting resistor and with only two electrodes in the arctube. Requires an ignitor like the high pressure sodium lamp (HPS).
Because its arctube design without the extra starting electrode is better (The arctube can be also shaped better), they have usually longer half life (Hours to 50% light output) and better color shift (Light output degrades to 50% and color significantly shifts only at or after the end of the lamp rated life, and not after only 100 hours of operation like the probe start lamps). Pulse start metal halide lamps, have also faster run-up and shorter hot restrike if operated in the correct equipment.
3. Ceramic metal halide (CMH): A pulse start metal halide lamp that have a ceramic arctube instead of a quartz arctube. Because the ceramic material can operate at higher temperature, the efficiency and color rendering can be increased. For the american market, the increased color rendering related only to the improved halide chimestry over the american quartz metal halide lamps (QMH) (Dy,Ho,Tm,Tl,Na in almost all CMH vs Na,Sc in all american QMH).