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Light reader, PAR meter, Optical Spectrometer?

w3rds

Member
To preface, Im a cheap bastard.

From what I have read, Lux is not an accurate light measurement for LEDs due to them measuring all light rather than just the necessary light for growing. That is why PAR ratings are used and I looked into meters, but I refer you to the preface.

My curiosity kicked in and I started looking a bit to see if my idea would work, but I havent seen anything so I might just be dumb. Anyway, my idea is to use my lux meter in combination with my optical spectrometer to verify that all the light(lux) is in the proper wavelength. The combination of the two giving an equivalent reading as spending the money on another reader.

1 to 10, how dumb of an idea?
 

Koondense

Well-known member
Veteran
Not dumb at all but practically impossible to make precise measurements like this. You would need some kind of processing power to calculate par readings.
 

w3rds

Member
Im looking less for an exact conversion as much as a way to compare two "similar models" to see which would be better, without buying a meter that will cost me as much as the light Im trying to buy.

I know that two "identical" lights can be drastically different and I have 3 different 300w, two with 1w and the third with 3w chips, I want to compare them to see optimal heights and max light output.
 

Koondense

Well-known member
Veteran
Maybe you can use the spectrometer for that, if it's digital and can be used with some pc software.
There's always a method to get some useful results with almost anything but don't expect miracles :)
 

Phaeton

Speed of Dark
Veteran
The minimum I need are: a blue meter, lumen meter, red meter, UVB meter, and PAR photon counter. When the cost is remembered ($1100) I wince, but they still give accurate readings nine years after purchase.
The red meter peaks in the center of red. The lumen meter peaks in the center of green. The blue meter peaks in the middle of blue. The UVB meter peaks at 300 nm. The quantum flux meter counts photons between 400 nm and 700 nm.

With incandescent lighting the spectrum curve was consistent with temperature and good guess could be made just from the green intensity, hence the widespread use of lumens for light measurement.
HIDs also have predictable spectrum from their advertised color temperature and color rendering index.
The spectrum of LED does not have this sort of predictable curve, the color of any particular diode has no bearing on the color of the diode next to it.

PAR ratings without specific spectrum is often less than useful. Low pressure sodium will measure a higher PAR per watt than any known discharge light. More PAR photons per watt than any other light, period.
Low pressure sodium will not grow plants, they will die. It is the ratios of frequencies, almost every wavelength gets used, some are better than others. A really high overall PAR reading is not a reflection of efficiency.

Learn which sellers can be trusted and take them at their word (do side by sides as well) for the output of their lights.
The real numbers have a minimum cost to get accurately. Doing the job with some of the tools missing can be misleading.
 

Koondense

Well-known member
Veteran
You're right on par.
It's actually the curve integral of a spectrum plot in the range of 400-700nm, so in practice can be anything in there. LPS is one great example, narrow band par with a high value and won't grow much.
 

brickweeder

Well-known member
Apogee Light Unit Converter App

Apogee Light Unit Converter App

Apogee has an app called Light Unit Converter that lets you select the light source (Sunlight, T5, MH, and HPS...no LED selections yet) and input various different units and it converts to the other units.

I use this as a rough converter only to get a sense of what my PPF converts to in lm/M2 or lm/ft2. Its a very nifty app from a kickass company.
 

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