# New light meter, a question



## Gizmo (Dec 6, 2010)

Found a deal on KSL.com (our local better version of Craigslist) on a Milwaukee SM700 (discontinued) light meter that was too good to refuse, so now I have my very own aquarium light meter  My questions are - the meter measures in Lux, I have a conversion algorithm for Lux to PAR with constants for various light qualities and types of bulbs. Is there a way to compare PAR to our touted WPG standard?

Note: PAR = photovoltaic active radiation
WPG = Watts per gallon
Lux = I don't know? (Listed in the manual as candlepower or something of that nature).


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## jrman83 (Jul 9, 2010)

Personally, I wouldn't worry about WPG. It was based off of basic systems that were the main type of lighting used years ago - and still use. It doesn't apply against all the types of lighting used today...like the T5HO light on your tank for instance. It's sort of like the 1" per gallon rule...it really only works with one type.

I thought about buying that meter but everyone on the website I asked about it said not to get it. I didn't see the big deal if you could convert LUX to PAR. I just decided to wait and get a PAR meter before I decided on new lights on two of my tanks. That is a couple of months away - got other things I'm doing first.


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## Gizmo (Dec 6, 2010)

I guess what I should say then is - is there some sort of benchmark or way I could find out how many PARs certain plants like?


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## jrman83 (Jul 9, 2010)

[email protected] said:


> I guess what I should say then is - is there some sort of benchmark or way I could find out how many PARs certain plants like?


You can convert levels of PAR into low-medium-high lighting and then look at the light requirements for a particular plant?


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## Gizmo (Dec 6, 2010)

jrman83 said:


> You can convert levels of PAR into low-medium-high lighting and then look at the light requirements for a particular plant?


Sounds perfect! You don't happen to know anywhere that would list PAR values for said low medium and high light, do you?

I'll be researching it right now. I'll let you know if I find anything...


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## jrman83 (Jul 9, 2010)

Start here:
PAR vs Distance, T5, T12, PC

A good read if you have a few minutes.


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## Gizmo (Dec 6, 2010)

jrman83 said:


> Start here:
> PAR vs Distance, T5, T12, PC
> 
> A good read if you have a few minutes.


Thanks a ton for the input  I'm going to try finding a Lux-PAR conversion constant for the bulbs I'm using and start taking some measurements.


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## phys (Feb 4, 2011)

Possibly, a good way to benchmark is to get your bulbs and the plants you have, then see how well they grow (while keeping track of new leaves and plant growth) under your light while keeping track of the LUX output. If you find the lux-par conversion, then you can easily give those numbers. You may also look into a lux-lumen conversion which i have seen but dont remember right now. Then those people who use a similar lighting setup as you will have an idea of how many lumens with a specific type of bulb is needed to grow plants at the rate you saw.


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