$379 too much for a PAR meter? How about $159?

[neuroslicer]

A meter for light intensity or PAR (photosynthetically active radiation) has been invaluable as I have transitioned from metal halide to LED illumination, but PAR meters can be expensive! Apogee sells a very nice one with a price of $379. This meter will measure PAR but will also record the values automatically at a pre-programmed time interval, will store the values, and also download them to your computer.

http://www.apogeeinstruments.com/mq-200-quantum-separate-sensor-with-handheld-meter/

But there's an alternative that's much cheaper. Apogee will sell you the identical PAR sensor that is used in their more expensive meter... but the price is only $139.

http://www.apogeeinstruments.com/sq-120-electric-calibration-quantum-sensor/

You can then get a $20 meter from Home Depot, Harbor Freight, Radio Shack, etc. and you're ready to record PAR.

The sensor is calibrated such that the reading in millivolts gets multiplied by 5.0 to give you the PAR value. Easy! If you want to record PAR.... get a notepad for less than a buck at Walgreen's, and pocket the remaining savings of $210... or go buy more coral and fish!

Best fishes!
JB

 

[oceanlife83]

Thanks for the information.

 

[ReefersEdge]

I was under the impression that par meters don't give accurate readings when used for reading LEDs?

 

[neuroslicer]

Apogee has calibrated their sensor against metal halides, T5s, LEDs and provides error correction factors to use to determine the correct values of PAR regardless of light source.

 

[OneReef]

From Apogee (maker of the PAR meter):


Email from Apogee Instruments on Measuring LED with Sensor:

"In regards to measuring LEDs with our sensor, there are some caveats to doing so. The following link shows the spectral response of our quantum sensor (http://www.apogeeinstruments.com/qua...lresponse.html). As the graph shows, Apogee quantum sensors underweight blue light, and as a result, photon flux measurements for blue LEDs will be too low. They also overweight red light up to a wavelength of approximately 650 nm, above which they do not measure, and as a result, photon flux measurement for red LEDs will either be too high (if the LED output is all below 650 nm) or too low (if a non-negligible fraction of the LED output is above 650 nm). Additionally, LEDs often have a very narrow spectral output, with a sharp peak of only a few nanometers. So, unless the quantum sensor has a perfectly flat spectral response, meaning it weights all wavelengths of light exactly the same, there will be errors. Electrically calibrated Apogee quantum sensors will likely provide a reasonable measurement for white LEDs because they are broadband, and because electrically calibrated quantum sensors are calibrated under CWF lamps. However, for narrowband LEDs, like red and blue, Apogee quantum sensors will not provide an accurate measurement.

As a less accurate method you can use the same spectral response graph as mentioned above to get a relative idea of the error. For example, a 450nm blue LED will have a relative response of approximately 0.8. Therefore, you can figure that the photon flux reading from the sensor is reading approximately 20% low. Just remember, this approach is only relative so give yourself a wide margin of potential error. A blue/white configuration should give you reasonable accuracy, particularly from the broadband spectrum of the white.

To sum up, sensors can be used to measure the relative output of an LED or bank of LEDs, in order to track variability in output with time or temperature for example. However, sensors should not be used to characterize the absolute output of LEDs (except for the possibility of white LEDs), to compare one LED to another, or to determine photon flux for plant growth for example. Ultimately, a spectroradiometer is the best instrumentation for characterizing LEDs."

 

[MrRyanT]

uhhhh.....yea, that's what I was about say