Apogee PAR sensor

[Geeray]

I purchased an Apogee SQ-120 sensor for measuring PAR in my tank. I hooked it up to a multi meter as recommended by apogee. The set up on my tank is as follows: The tank is 72"x24"x24" and in one 24x24 section I have a hydra 52 mounted 12 off the water line running at 100% on all channels. In another section I have 2 AI Sol Blues mounted 12 off the water running at 100% on all channels. When I measure par at 12 below the water line I get ~200 in the hydra 52 section and ~300 in the Sol blue section. To me this seems low compared to what others have posted with similar lighting configurations. Any thoughts or opinions? Perhaps my sensor is bad?

[Geeray]

Sorry I forgot to mention all readings were directly under the lights...

[gcarroll]

The difference is optics. The sol uses a combination of narrow optics (center 4 pucks)
and wide able optics (outer 4 pucks). This creates a 12" x 12" hotspot directly below the fixture. The Hydra 52 uses a wide angle for all. This creates a more even light throughout the lighted area.

[mcgyvr]

according to their site you should see 450-500 par at a depth of 24" directly centered under the fixture.

and there are many..many reasons for possible discrepancies... from excessive water movement, to bad sensor, to bad lights, to cloudy water, to meter calibration errors, to blah blah blah..

[Geeray]

according to their site you should see 450-500 par at a depth of 24" directly centered under the fixture.

and there are many..many reasons for possible discrepancies... from excessive water movement, to bad sensor, to bad lights, to cloudy water, to meter calibration errors, to blah blah blah..

I do have a ton of surface agitation but I'm not sure how much of an effect that has.

[markalot]

You should turn off all the pumps when measuring PAR, it can be really hard to judge when the number is bouncing around. IMO.

[kurt_n]

I do have a ton of surface agitation but I'm not sure how much of an effect that has.

Fairly large effect, from what I've seen. Like markalot mentioned, I've found it's tough to pick a number for the "average" reading when the numbers are jumping all around. I've always just turned all pumps/powerheads off when doing measurements. Give it a try - you'll probably be surprised.

[gcarroll]

When one number is bouncing around in the 200s and the other in the 300s, it doesn't matter! there is a major difference. I just can't beleive you guys would even suggest that the difference could be surface aggitation.

When AI interduced the Sol, they wanted to bill it as a competitor to a 250w metal halide. To achieve those 250w MH PAR numbers, they used narrow optics so when tested in a way that the OP is stating, they would get those nice results. Measure outside that 12" x 12" area and you will see the big difference. Surface aggitation or not!

[pwreef]

A lot of manufacturers state PAR without water. 24 inches from the fixture with and without water is huge difference.

[kurt_n]

When one number is bouncing around in the 200s and the other in the 300s, it doesn't matter! there is a major difference. I just can't beleive you guys would even suggest that the difference could be surface aggitation.

When AI interduced the Sol, they wanted to bill it as a competitor to a 250w metal halide. To achieve those 250w MH PAR numbers, they used narrow optics so when tested in a way that the OP is stating, they would get those nice results. Measure outside that 12" x 12" area and you will see the big difference. Surface aggitation or not!

I'm not saying your wrong... in fact I agree with you. I'm just saying it's tough to get accurate numbers when there's surface agitation.

[Geeray]

A lot of manufacturers state PAR without water. 24 inches from the fixture with and without water is huge difference.

Any know if AI ratings are with or without water?

[mcgyvr]

Any know if AI ratings are with or without water?

You've got a PAR meter... Let us know ;)

[dudz]

Where can I buy a Apogee PAR sensor on the internet for international dispatch please ?