Using cheap lux-meter for "ball park" PAR measurements possible?

Hello.

I've found a thread(can't recall if it was on rollitup or not) in which a person was modifying a lux-meter to get it to reflect a PAR value, the thread was very long and in the end I was nothing but very confused.

But my reasoning is that if I had a lux-meter and I knew the exact spectrum of my light source(which I do since I have the datasheet for my specific COB LED), then shouldn't I be able to take a lux-meter reading and convert that into a "ball park" PAR value?

I don't know but I can't afford a Quantum sensor and I really, really want to find out some characteristics of my own built grow light. Is a low-cost close-to-PAR meter a pipe dream?

The person in the thread I mentioned had gotten a book of samples from a company which produces light filters and with a lot of calculations(he said) and experimentation he found filter combinations that resulted in sort of a PAR spectrum but in the end he didn't consider it a good solution.
He also changed the actual light sensor in the lux-meter.

That is another option I have begun looking into, finding a light-sensor that out of the box would have a spectrum response close to that of a PAR measurement, according to Wikipedia, "PPF values all photons from 400 to 700 nm equally", that makes me optimistic of actually being able to find a solution for this.

I reckon that I must be far from alone to have been thinking about this, have anyone else thought of something like this and have you come to any conclusion or result?

Regards
 
I haven't read it yet but I will but the introduction of this document is very exciting:
"Dependencies have been shown and conversion factors have been determined, which allow
to estimate PPFD, YPFD and radiometric power density of white LED light according to the
known illumination in lux. A technique for estimating photosynthetically active radiation,
which has an adequate accuracy for the task of illuminating plants, has been determined."

I do not have enough likes to be allowed to post links or URL's but if you search for:
"An easy estimate of the PFDD for a plant illuminated with white LEDs: 1000 lx = 15 μmol/s/m2"
you will find it.
 

nfhiggs

Well-Known Member
Hello.

I've found a thread(can't recall if it was on rollitup or not) in which a person was modifying a lux-meter to get it to reflect a PAR value, the thread was very long and in the end I was nothing but very confused.

But my reasoning is that if I had a lux-meter and I knew the exact spectrum of my light source(which I do since I have the datasheet for my specific COB LED), then shouldn't I be able to take a lux-meter reading and convert that into a "ball park" PAR value?

I don't know but I can't afford a Quantum sensor and I really, really want to find out some characteristics of my own built grow light. Is a low-cost close-to-PAR meter a pipe dream?

The person in the thread I mentioned had gotten a book of samples from a company which produces light filters and with a lot of calculations(he said) and experimentation he found filter combinations that resulted in sort of a PAR spectrum but in the end he didn't consider it a good solution.
He also changed the actual light sensor in the lux-meter.

That is another option I have begun looking into, finding a light-sensor that out of the box would have a spectrum response close to that of a PAR measurement, according to Wikipedia, "PPF values all photons from 400 to 700 nm equally", that makes me optimistic of actually being able to find a solution for this.

I reckon that I must be far from alone to have been thinking about this, have anyone else thought of something like this and have you come to any conclusion or result?

Regards
Most popular white LED spectrums can be converted from Lux to PAR (within about +/- 10%) by dividing the Lux reading by 70. As long as the Lux meter is relatively accurate, you can get a reasonable estimate of your PPFD.
 
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