# Light meter



## Greenleaves42 (Apr 16, 2016)

Hi, i live in the Uk and light levels vary alot! I also like to use lights where possible, im not quite sure on light meters(camara) and all the different units of measurement, i would like to start recording something though. Is there anything on the market that i can leave on one of my plants that gives me a reading for the whole day as an average? Due to the changing conditions here you could have a bright 10mins then gloomy 20mins...it constantly changes so im not quite sure on how that converts to a measurement i can use.

If possible i would like to record an average and work out the useable energy for that day? Im thinking a bit like how much battery charge you get off a small solar panel i want to know in effect what kind of light charge my leaves are getting....perday.

Im really not sure if this is what light meters record? In the ideal world id like one on every pot so i can move plants around or add extra lights etc.

Can anyone shed some.....light 

Matty


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## gonewild (Apr 16, 2016)

You need a data logger meter.
one example;
http://www.pro-measure.com/Data_Logging_Light_Meter_p/lx-1128sd.htm


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## naoki (Apr 16, 2016)

What's your budget? This will do what you want for $195.
http://www.apogeeinstruments.com/sq-420-smart-quantum-sensor-usb-output/
This can do logging, and I think the software will calculate the total amount of plant relevant light per day (called daily light integral, DLI).

Below this price, you have to use foot-candle/lux meter (which is more relevant for human eyes) instead of plant relevant PAR meter. If you are a little handy, you can make a logger with Arduino for about $50 (or less).

http://www.instructables.com/id/Highly-sensitive-Arduino-light-sensor/
http://minisystem.blogspot.com/2011/12/logging-lux-data-with-hacked-dx-light.html

With sun light, you can approximately convert footcandle/lux to the plant relevant unit (photosynthetic photon flux density, PPFD), so no need to have expensive PAR meter. http://www.apogeeinstruments.com/conversion-ppf-to-foot-candles/

Here is a link to info about different units of light intensity:
http://www.gpnmag.com/wp-content/uploads/16_TechnicallySpeaking_GPN0913 FINAL.pdf


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## Happypaphy7 (Apr 19, 2016)

How about the light meter app on iphone?
I bought it as a quicky just for 1.99, but I wonder how accurate it is.

A member here says his reading seems accurate, but I'm not so sure about mine. May I'm not using the right kind of paper as a diffuser the app recommends to use for better reading, but the reading comes out slight less than 1000 fc about 8 in under my T8 ( 4 bulbs) set up.

This is significantly lower than sunlight through the window glass, but a handful of paphs under T8 were getting bleached. hence I was worried and hot this cheap light meter.


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## gonewild (Apr 19, 2016)

Phone app light meters are not accurate nor are the consistent in the amount of inaccuracy. They do not give results you can trust for plant growth and actually can be very misleading.

They are accurate for what they are designed, calculating photographic exposure.

I tried several apps and then bought a $30 light meter that is actually very accurate or at least close and consistent.


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## gonewild (Apr 19, 2016)

Light meter apps were discussed previously:

http://www.slippertalk.com/forum/showthread.php?t=35138&highlight=phone+light+meters


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## Happypaphy7 (Apr 19, 2016)

Thanks, Lance.

I wasted my $2, then. I mean that's nothing, but still. I guess you get what you pay for. lol

The $30 product, is it something that I can get here in the US??
I just don't want to spend too much money for it.
I mean, a couple of plants that went slightly bleached, but everything else seem happy so far, so I really don't care about exact fc measurement, but at the same time, would be nice to know.


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## gonewild (Apr 19, 2016)

Happypaphy7 said:


> Thanks, Lance.
> 
> I wasted my $2, then. I mean that's nothing, but still. I guess you get what you pay for. lol
> 
> ...



I bought mine on Amazon when I was in Calif. I post a link later.


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## gonewild (Apr 19, 2016)

gonewild said:


> I bought mine on Amazon when I was in Calif. I post a link later.



http://www.amazon.com/Dr-Meter-Digital-Illuminance-Light-LX1330B/dp/B005A0ETXY

Looks like the price went up a little. It's easy to use. The cabled sensor makes it easy to get in tight spots.


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## naoki (Apr 19, 2016)

Yes, the price of LX1330B fluctuate quite a bit on Amazon, and it is almost at the record high price now. You can still find the same thing from eBay at around $30 (which used to be the price from Amazon). There are several rebadged products, but you can search for LX1330B. Actually, there appear to be two different styles of sensor: one with half dome with an orange cap, and the other with flat white part. I don't know the difference, but the former (domed sensor) is the one I've used.


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## gonewild (Apr 19, 2016)

naoki said:


> Yes, the price of LX1330B fluctuate quite a bit on Amazon, and it is almost at the record high price now. You can still find the same thing from eBay at around $30 (which used to be the price from Amazon). There are several rebadged products, but you can search for LX1330B. Actually, there appear to be two different styles of sensor: one with half dome with an orange cap, and the other with flat white part. I don't know the difference, but the former (domed sensor) is the one I've used.




Mine is domed with orange cap.


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## Happypaphy7 (Apr 21, 2016)

gonewild said:


> http://www.amazon.com/Dr-Meter-Digital-Illuminance-Light-LX1330B/dp/B005A0ETXY
> 
> Looks like the price went up a little. It's easy to use. The cabled sensor makes it easy to get in tight spots.



Thanks.


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