Dang it! Another question about (T5) light.

[justjill3]

Ok, so, I went out and bought the light meter from the hydro guy. It does not require a battery and uses the sensor attached by a wire to the meter. The sensor looks like a pickle with a hula hoop all in plastic.

I'm sittin' here with the instructions opened up . . . and I still don't get it! I noticed that the instructions take into account whether or not the light source is solar or HID; or flour. However, the flourescent grid is calibrated from 0-1000 footcandles. With 4 T5s, I KNOW I will have more than 1000 footcandles.

I think I know the answer! Because the "flourescent" scale cannot accommodate a rating higher than 1000, I HAVE TO move to the sun/HID scale. This device was probably designed before the intro. of the T5 tube. HIDs were. Soooo, the instructions have been updated to account for HIDs, but NOT for the newer T5s.

Quick! Someone tell me if I understand how this thing works or not.

The bottom line is I have 4 48 ft. T5s with a reflector. I have phals., oncidiums, a den. big.; and catts. How close does everyone have to be to the light?

Rooosssssssss!!! Help me!

[FinnBar]

i'm no ross but here's my two cents worth

Because the "flourescent" scale cannot accommodate a rating higher than 1000, I HAVE TO move to the sun/HID scale.

i'd say you're right, it's probably just switching to smaller scale.
i know some light meters have an option to measure UV-rays as well but i don't think that's the case here. those meters are usually way more expensive..

the light meter should give you good indication for placing your plants. distance isn't everything though, it's also about how high light lovers provide shadier conditions for lower light ones.
some of your setup would be nice!

[goodgollymissmolly]

I admit that I have never seen a light meter that includes measurement of specific wave lengths (light sources, if you wish). However, here is what you can do.

Light intensity is a function of the square of the distance from the source. So measure the light at a distance that that can be measured with your meter. For example, move a foot away and get a reading...chances are that will be far enough to get less than 1000fc but move farther if needed. Once you get the reading, then for each time you move one-half the distance towards the light source your light will increase by a factor of 4. So lets say you get exactly 1000fc at 1 ft. Then at 6 inches you have 4000fc and at 3 inches you have 16000fc. These are examples...you are not likely to values nearly this high, but it shows how important it is to put the plants near the source when dealing with relatively weak sources like flourescent.

[Ross]

Originally Posted by justjill3

The bottom line is I have 4 48 ft. T5s with a reflector. I have phals., oncidiums, a den. big.; and catts. How close does everyone have to be to the light?

Jill, the t5's are close enough in output to the metal halide/sodium bunch you can use the HID scale. As has be stated here, you may be surprised by the readings. 4 - 48" High Output t5 tubes in combination should put out 20,000 lumens. Divide that by 12.57 (close enough) to get foot candles - AT THE BULB! as stated above light drops off quickly as you move further away. Your lights probably emit approx 1600 (a bit less) at the bulbs or really close to them. Use that to find the scale that works best for you and stick with that. Hope this helps.

[justjill3]

Thank you all. I'm sorry it has taken so long to reply, but thinks have gotten quiet hectic. It's 5:18 AM and I've only been typing for 5-10 min. For every word I've typed correctly, I've typed at least one incorrectly. Will write more later. Thank you again.