Spectroradiometer that can measure PPFD from LEDs


#1

I’ve been researching how to measure photosynthetic photon flux with equipment that can handle LEDs rather than just broad spectrum light sources like incandescent or fluorescent lamps. From what I can tell, you need a spectroradiometer to do it properly. Tonight I came across a company that sells a hand-held unit that can measure PPFD. It costs $1,399. Not cheap, but compared to lots of lab grade test equipment, it’s relatively affordable.

This is the International Light Technologies ILT350 Spectroradiometer:

https://www.intl-lighttech.com/products/ilt350-spectroradiometer

The problem with old-school PAR meters and LEDs is that the older PAR meters use sensors that make lots of assumptions about the light spectrum they will be measuring. That generally worked well with traditional incandescent and fluorescent grow lights. But, combinations of narrow spectrum LEDs confuse the old meters. A spectroradiometer doesn’t have that problem.

Does anybody know of other spectroradiometers that can measure PPFD?


Use of RGB LED strips for MVP
#2

Hi @wsnook

That looks like it does more than just PPFD (which is just a photon count at the canopy) That meter breaks down the spectrum itself (blue/red levels etc…).

If your looking for just PPFD then Apogee seems to be a popular brand. You would need the 500 series which can handle the handle the LED spectrum range.

I recentently came across a portable spectrometer called lighting passport that looks promising but also seems too good to be true given it’s small size. The Pro version which is much more expensive has some sort of “flicker” compensation which could be important if you’re dimming the lights.

Getting a photon count at the canopy level is very important…knowing the actual spectrum would be amazing.


#3

Yeah, that’s what I had in mind by the “…to do it properly” part. From what I can tell, it seems like most the cheaper meters use a broad spectrum sensor with a non-linear response curve and maybe IR and/or UV filters. From what I’m reading, it sounds like that kind of gear isn’t likely to give you a useful number if you point it at light that’s coming from a combination of narrow spectrum LED sources.

I said PPFD, but I’m also thinking about things like blue to red to far red ratios.

Thanks for the links. I’ve seen some of Apogee’s stuff in the past. On the quantum sensor page you linked to, their marketing blurb for the original quantum sensors starts off with, “Great for measuring all light sources except red and blue LED colors…” But, the newer full-spectrum one looks like it would be better for LEDs. Clicking around Apogee’s other products, it looks like they also sell spectroradiometers in the $2700 to $5000 range. Ouch.

I think the AsenseTek Lighting Passport one might be the same meter that I saw in some of Mike Wood’s articles. I was wondering what that was. Looks like Allied Scientific Pro sells them for about $2000 or $2800 depending on whether you want a calibration certificate. Thanks!


#4

Hi, I’m working on a light source control based on Chlorophyll absorption. I expect a couple of moths more to share my work here but, I can for sure tell you that you only need a spectrometer like this one

I hope that link can help you and give you more horizons to explore.


#5

Nice link. Reminds me of Spectral Workbench (related thread: DIY spectrometry for calculating PAR of cheap LEDs? ).

For anyone who’s curious to learn more about this stuff, I just came across an excellent collection of tutorials on measuring light by Gigahertz-Optik (test equipment company). The tutorials are well written and very comprehensive–including a section on plant physiology.


#6

Thank you for the links, they’re very useful. I have also experience with the open spectrometer designs from
Publiclab, They’re awesome for the beginning, but I prefer to explore the guts of how we can translate light into data by pixel interpretation. The python program of the link that I shared with you can give us a lot of hints for reverse engineering and also give us a hand incorporating some other functions of computer vision.