Do you own a PAR meter?

[MoonShadows]

I decided to write this post after reading a post by @Rey who mentioned his PAR meter. Do you own a PAR meter? What brand and where did you buy your PAR meter? Are you pleased with it? I want to buy one, but the prices vary from real cheap to real expensive. I don't mind going for a few bucks, but if I do, I want one that is worth it.

 

[marlingardener]

Question from the technically inept--what is a PAR meter? We may have one since there are items in my husband's workshop that I can't identify!

 

[MoonShadows]

Good question @marlingardener

Most folks think PAR is when you complete a golf hole in the recommended number of strokes.

Photosynthetically Active Radiation (PAR) meters measure light intensity within the spectrum which plants use most to photosynthesize (excluding UV light) from 400 to 700 nanometers which covers both the blue(used for vegetative growth) and red(used for flowing and fruiting) spectra. These meters tell you how well your grow light(s) are covering your grow footprint and at what intensity so you can make adequate adjustments depending on the plants needs. The unit of measurement from a PAR meter is micromoles per second (μmol/s). If you know the needed micromoles per second (μmol/s) requirements of your plants at various stages, then you can adjust your light settings to maximize growth and plant output.

It is like measuring Lumens for humans which is the measurement of light intensity as we perceive it through our eyes. You can have very bright lights on your plants but if the PAR intensity is insufficient, they will not get the light they need for proper growth. Most LED plant grow lights (and florescent grow lights to a lesser degree or less effective levels) are made up of the blue and red spectra with less of other spectra that plants don't make as much use of. The blue and red spectra alone will actually look like there is not enough light for plant growth...to the human eye...but, to a plant, it's like a day at the beach!

 

[Greenhorn]

I use a little older model of this, not exactly a PAR meter, but it's a high level start kind of. I see the spectrums I think your talking about on some of the light packaging. I think my practices and environment have too many variables to get to that level.

I use my light meter to determine basic sunny day values - cloudily day values, sunny day values - cloudily day values behind shade cloth and then combinations of the same inside my little greenhouse. I use shade cloth close to reflective walls near both my greenhouse and other growing locations and also on the south facing front. I'm always on the lookout for good literature related to light values, I've only been able to find general information.

https://www.hydrofarm.com/p/LG17010

 

[marlingardener]

Moonshadows, I have never completed a golf hole in the recommended number of strokes. In addition to being technically inept, I am a complete loss at sports.
Thank you. Your simple and clear explanation now has me understanding PAR.
How wonderful to learn something new from fellow forum users!

 

[MoonShadows]

Ahhhhhhh...my please @marlingardener

I played a lot of golf in HS and college. I was actually on my HS Golf team. Actually got "fairly good" at it...being able to shoot in the 80's, but I haven't played golf in almost 40 years.

 

[DirtMechanic]

For those interested, 350-750 nanometers describes the radio frequency of visible light, and this machine is very much tuned to that end by reducing the the high and low to cover 400-700. Some will be interested in the heat wavelength of infrared heat as they impact growing which is bigger than 750nm and some will find 350 nm and smaller interesting as it relates to pathogen control.