Contributor
Andy, many here will learn something new from that. But accepting that it is the same time over hundreds of miles of
East- West direction is certainly not "accuracy". A noon mark reading corrected with an "equation of time chart" is more
accurate. A farmer knowing a frost is coming overnight knows his crop must be half gathered by noon or ...he has to get
some help. He takes no comfort from knowing that he can watch Laverne and Shirley at the same time as someone
hundreds of miles away !
Contributor
Bruce please update this in 50,000 years. By then I may decide to upgrade my lights to the same brand. I am not sure if this is just 50,000 years or 50,000 years of run time? I suppose the De Havilland law may apply here?
Bill D
Last edited by Bill Dufour; 06-27-2020 at 12:14 PM.
Contributor
Sorry to be repetitive, but you do realize the lifetime is 50,000 hours not years?
[OP]
Contributor
Originally Posted by Doug Garson
That was my whole point. Someone should have proof read their claims.
[OP]
Contributor
Look at the Harbor Freight hanging shop LED shop light. That thing puts out 5000 L. Need to wear sunglasses when they are on.
Contributor
When I look up that bulb on the Home Depot website it says 50,000 hours, maybe they corrected it since you saw it? http://ETi-48-Watt-4-ft-Linear-LED-T...1162/312096303
Maintenance free with no tubes to replace; lasts up to 45 years or 50,000 hours of continuous use
Contributor
I agree that it probably should have been 50,000 "hours". That's a pretty standard figure used for LED lighting.
LED's don't "fail" in the normal sense, their light output just gradually degrades. The "lifetime" number given is typically the time until the light output drops to 70% of its original output.
Theoretically, a perfect LED will last forever, but impurities in the semiconductor material, heat, voltage spikes, etc., cause gradual degredation. Quality products last longer.
Contributor
Crei is a very reputable manufacturer, but I find them hard to find in the consumer market. I've been pretty happy with Feit LEDs in the house, but only last week got some 4-foot tubes to try.
Contributor
Home Depot carries them now.
- After I ask a stranger if I can pet their dog and they say yes, I like to respond, "I'll keep that in mind" and walk off
- It's above my pay grade. Mongo only pawn in game of life.
Member
I may have to give up on not buying the lights without pull chains. No pull chain = no lumens.
Moderator
BTW, Lights of America was the company sued by the FTC for their claims of light output and life expectancy of LED fixtures:
https://www.ftc.gov/news-events/pres...lights-america
Maybe the have changed their ways by now.
I went through the research on the pros and cons of different types of lighting when building my shop a few years ago. I decided on T5 high output bulbs. The specs are great, the reviews were good, and the light is excellent. Although more expensive, T5HO bulbs are brighter than T8 and T12 bulbs. https://www.lighting-pros.com/t5-t8-t12-buying-guide
Measuring the lumen output of a large bulb requires a huge and extremely expensive integrating sphere. I understand some lighting manufacturers don't even measure but advertise based on the estimated theoretical output of the LED elements in the fixture. Some making and selling inexpensive LED fixtures apparently source the tiny LED elements from the lowest bidder and the light output from a fixture you buy today may be different from one bought last year from the same company. I purchased and measured the light output from several LED fixtures and the results were discouraging.
I also compared several types of T5 fixtures with the light meter. For bulbs, a mirrored fixture is the best since less light is wasted by being absorbed by the fixture. The lumen numbers are a measure of all output from a source, including the side of the bulb that is away from the room and towards the inside of the fixture. Another thing I really like about the T5 fixtures I bought is the electronic ballast, designed to optionally light just two of the four bulbs in each fixture unless I flip an extra switch to turn them all on at once. The brightness is excellent with 1/2 the bulbs but a flip of a secondary switch gives me twice the light for special needs. More light can help a lot as eye age.
I installed nine T5 fixtures in my shop with 36 T5HO bulbs.
JKJ
Member
Noon marks are hopelessly inaccurate on cloudy days, and during eclipses or earthquakes. And each only tells solar time for one longitude, once per day.
Leap seconds are an excellent reminder that solar time, no matter how precisely measured, is not a very accurate representation of time.
The laws of physics do not operate on solar time, but ironically, solar time does, in a very complicated way, operate according to the laws of physics. Solar time is basically a measurement of the period of rotation of the earth, relative to its orbit around the sun. The rotational period of the earth, however, depends on many unpredictable occurrences, primarily those that impact the rotational inertia of the earth. The period is decidedly and demonstrably non-constant.
The farmer today would not know that the first frost was coming on a particular night unless he had access to an accurate weather forecast, produced by computer models fed by accurate weather measurements via communication networks, all of which require time measurement and coordination much more precise (and continuous) than that of a noon mark.
Furthermore, many of today's farm workers would not reach the farm if not for navigation assisted by GPS, which uses atomic clocks completely independent of solar time, excepting only their initialization to 1980. GPS time does not use leap seconds, to retain a pure, physical time necessary for such calculations.
Thus, the farmer today would likely lose a chunk of his crop if he had only noon marks to rely upon.
-- Andy - Arlington TX
Contributor
I have not said that noon marks are as acurate as modern clocks and watches. But it is a fact that clocks were set by
noon marks. Barometers ,thermometers, and weather "signs " have been around a long time. What's NEW is pretty
"weather girls". I can remember family gatherings where someone would ask the time ...and get a chorus of different
numbers. Just because some of the watches in the room were gold, their children use them now. Yes, they are people
who refuse the extreme accuracy of animated "The Simpson's" watches rewarded to those who are wealthy enough
to buy 8 gallons of gasoline at one time! They "cling to the old ways".
Member
Mel,
I'm sorry, I mistook your statement:
"...But accepting that it is the same time over hundreds of miles of East- West direction is certainly not "accuracy". A noon mark reading corrected with an "equation of time chart" is more accurate. ..."
as indicating that a (corrected) noon mark reading is more accurate than the timekeeping means I had mentioned, including atomic clocks, instead of simply indicating that a corrected noon mark reading is more accurate than a non-corrected noon mark.
My mistake!
Basically, we use the concept of time to coordinate multiple events, whether local or distant.
How tightly the events need to be coordinated determines the required accuracy of the time measurement.
-- Andy - Arlington TX
Member
That is correct. The FTC sued Lights of America for their claims of light output and life expectancy of LED fixtures. I don't have any those. I only used Lights of America flourscent fixtures which based on the date of installation I wrote on them far outlasted the inexpensive fixtures from Home Depot and Lowe's. (really, something from Walmart was better the HD/Lowe's)
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