PAR TEST READINGS – By Sanjay Joshi, Ph.D. (Feature Article: LED Lighting Tests: )
Orphek PR-156 UV LED Array
“The Orphek array PR-156 is one of the newer models that includes 4 UV LEDs, in addition to the blue and white LEDs.
A total of 60 LEDs running at around 2W each make up the complete array.
As tested the Orphek drew 110W of power.
As seen from the light distribution, there are large areas at 24″ and 36″ where the PPFD values exceed 200.
This clearly shows the impact of the optics and will allow these fixtures to be well suited for deeper tanks and mounting higher to get larger spread if desired.
As LED lighting moves further into the mainstream, there a lot of new choices available to the aquarist. Hopefully this data will help the aquarist make an informed choice on what to expect from the individual LED fixtures and how best to utilize them to achieve the desired coverage and light intensity. In my experience a target of approximately 100 micromoles/m2/sec at the bottom of the tank will provide enough of a light gradient to satisfy a wide range of corals. Multiple fixtures will provide regions of overlapping light distributions which provide an additive effect thereby increasing the light intensity and area covered.
Each of these was tested using the same set up as my previous reflector tests, using a 3’X3′ grid with a spacing of 3″ in the X,Y direction. The fixtures were centered on this grid, and PAR was measured as PPFD (Photosynthetic Photon Flux Density) in micromoles/m2/sec using a LICOR 1000 data logger and a LI-192SA underwater cosine corrected sensor calibrated for both air and water. The data logger was set to average 5 readings for each data collection point. The data was imported into Microsoft Excel for analysis and the data was plotted to display the light spread and intensity at various distances. 4 plots of the data with 2 plots at each distance were generated showing:
- A 3-D surface plot showing the actual PAR values recorded
- A contour plot viewing the surface from the top showing the distribution
The fixtures were tested for light spread and intensity at 24″and 30″, unless otherwise noted. Power draw was measured with a Kill-A-Watt meter.