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Old 04/06/2007, 05:35 PM   #4
ReeferAl
Premium Member
 
Join Date: Dec 2001
Location: Fond du Lac, WI
Posts: 2,040
Quote:
by hahnmeister
As for reflectors, I do use the dreaded PFO mini-pendants due to their size, but my results were not taken with a reflector. far.
You missed my point. You are running your bulbs in a different reflector, a smaller one. This results in a different operating environment that may be causing the bulbs to lose output faster than they do in my setup with RO III reflectors. Your output falls to 65% of original in 1 year while my output with the same bulbs, same ballasts, same photoperiod, but different reflectors falls only to 75% in 1 year. That suggests that the PFO mini reflectors may be causing premature wearing out of the bulbs.

As far as the measurements I am getting, a comparison with the measurements from someone else is meaningless. As you say, mine were measured in the reflector, not separately. Most important however is that the distance of the light meter's receptor from the bulb is undoubtedly different between my measurements and those of anyone else. My measurements were taken about 7 in from the glass of the reflector, which would be even further from the bulb itself.

The measurements I obtained are not really that relevant by themselves. It is the percentage of original light output over time that was the important point. For example, I could have had measurements twice what I had if I had made the probe holder shorter.

to test the bulb output over time with a reflector makes it hard to be sure of the accuracy because a slight change in sensor positioning can change the results

That is true, but as I mentioned in the article, with the probe holder I built, I was able to get reproducible measurements that varied by less than 1%. The holder gave me a consistent distance and then with each measurement I "fished around" with the probe holder for the highest value I could find. This eliminated the requirement of knowing the precise position of the probe for each measurement. Incidentally I would note that it was not always directly under the center of the bulb.

Allen


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