PAR Meter

2175 Views 8 Replies 5 Participants Last post by toffee, Aug 28, 2012

toffee

Discussion Starter · Aug 27, 2012

Anyone in SoCal that has a PAR Meter? Like to rent for couple of days and do some measurement. I am in low desert but frequent LA and OC.

Thanks

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FriendsNotFood

· #2 · Aug 27, 2012

Become a member of SCAPE. They have a PAR meter they lend out.

http://scapeclub.org/forum/cmps_index.php

http://scapeclub.org/forum/showthre...k-it-out-for-use&highlight=par meter checkout

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Or, rather than rent a PAR meter, just buy a cheap lux meter from Amazon or Ebay, and use it to measure the intensity in lux, in the air, then divide by 61 to get a good approximation of PAR, and multiply by 1.1 to get a good estimate of the PAR in a tank of water at the same distance.

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Higher Thinking

· #4 · Aug 27, 2012

Hoppy said:
Or, rather than rent a PAR meter, just buy a cheap lux meter from Amazon or Ebay, and use it to measure the intensity in lux, in the air, then divide by 61 to get a good approximation of PAR, and multiply by 1.1 to get a good estimate of the PAR in a tank of water at the same distance.

I thought lux was totally separate from par? What changed so that they are now only one function away from each other?

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GeToChKn

· #5 · Aug 27, 2012

Higher Thinking said:
I thought lux was totally separate from par? What changed so that they are now only one function away from each other?

The fact that Hoppy bought one, took it apart, tried to make it an underwater one, did a bunch of calculations on known lights he has, etc and came out that it's easier to just use a lux meter and go by the math he found out in his-converted-lux meter.

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toffee

Discussion Starter · #6 · Aug 28, 2012

Hoppy said:
Or, rather than rent a PAR meter, just buy a cheap lux meter from Amazon or Ebay, and use it to measure the intensity in lux, in the air, then divide by 61 to get a good approximation of PAR, and multiply by 1.1 to get a good estimate of the PAR in a tank of water at the same distance.

GeToChKn said:
The fact that Hoppy bought one, took it apart, tried to make it an underwater one, did a bunch of calculations on known lights he has, etc and came out that it's easier to just use a lux meter and go by the math he found out in his-converted-lux meter.

Oh thanks guys, there are lots of lux meters on Amazon from $30+ to $160+ any suggestion?

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GeToChKn

· #7 · Aug 28, 2012

Here is Hoppy's thread on it

http://www.plantedtank.net/forums/showthread.php?t=179789

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Hoppy

· #8 · Aug 28, 2012

Even the Quantum PAR meter just gives you an approximation of PAR, because its sensor does not have a response curve that exactly matches what we want to measure for PAR. A Lux meter isn't close to having as close a response curve as the Quantum meter, but as long as you are measuring light from typical planted tank light sources, 5000-10000K fluorescent or LED or PC bulbs, you can use the same conversion factor to go from lux to PAR. If you were experimenting with light sources heavy on red, near infrared, near UV, or blue or red light, the PAR reading you would get with a lux meter would be very inaccurate. But, almost none of us want to do that, so the lux meter is accurate enough. And, it can cost as little as $10 at Amazon, plus shipping.

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toffee

Discussion Starter · #9 · Aug 28, 2012

Hoppy said:
Even the Quantum PAR meter just gives you an approximation of PAR, because its sensor does not have a response curve that exactly matches what we want to measure for PAR. A Lux meter isn't close to having as close a response curve as the Quantum meter, but as long as you are measuring light from typical planted tank light sources, 5000-10000K fluorescent or LED or PC bulbs, you can use the same conversion factor to go from lux to PAR. If you were experimenting with light sources heavy on red, near infrared, near UV, or blue or red light, the PAR reading you would get with a lux meter would be very inaccurate. But, almost none of us want to do that, so the lux meter is accurate enough. And, it can cost as little as $10 at Amazon, plus shipping.

First off, it will be for a 8ftx2.5ftx20"(l,w.d) tank that will act as room divider, viewing 3 sides and open top ("humidifier" for the living area). Top of tank about 7ft from ceiling. I live in the desert, so plenty of sun. I want to use exclusively low light plants under a very low tech environment.

I am thinking of using solartube as primary light source and LED for evening. I have high ceiling and Mrs. is not agreeable to have solartube extended closer to the tank like the picture below. I want to measure the PAR value at 6-7ft from end of different sized solartube. I am thinking of two or three 14" tubes. As for LED, I am planning to use 6 units of Current USA prolumens. They have limited output but they have very small footprint and can be placed right above water.

My whole idea may not work, so doing some measurement as part of planning is important to me.

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