# PAR meter recommendations...



## Hoppy (Dec 24, 2005)

Look for the Apogee Quantum 200, which I believe is the one most commonly used. And, it works great.


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## Naekuh (Oct 19, 2011)

+1 also looking for a cheap PAR meter.



Hoppy said:


> Look for the Apogee Quantum 200, which I believe is the one most commonly used. And, it works great.


Hoppy the SQ series OK?

Model SQ $139.00

Is the multi channel recommended?


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## Hoppy (Dec 24, 2005)

Isn't the SQ series just the light sensor, so that you need a very good milivoltmeter to read it out?


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## Naekuh (Oct 19, 2011)

Hoppy said:


> Isn't the SQ series just the light sensor, so that you need a very good milivoltmeter to read it out?


Meh reading vendors site its says your right..

you need the MQ's ... 

those are 300 dollars as the ops says... :biggrin:

I was hoping there were something a bit cheaper... :hihi:


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## DKRST (Jan 20, 2011)

Just got my MQ 200 about two weeks ago. Under $300, free shipping, shop around the net and wait for a sale, but still not much below $300. I think mine was $289 or so. Easy to use, auto shut off. I purchased to do some research projects at work. If you get this one and plan on using it a lot (for the local aquarium club, etc), I recommend buying the telescoping "arm" to help take measurements. I made an arm by twisting some 10 gauge copper wire (w/power drill). Works pretty well, but not quite rigid enough and hard to store @ 3' long!


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## dundadundun (Apr 8, 2010)

Hoppy said:


> Isn't the SQ series just the light sensor, so that you need a very good milivoltmeter to read it out?


let me get this right. the sensor reads @ 5umols per mV, so a multimeter that's capable of reading @ .1mv should give me accuracy of .5umols +/-(?)%, correct?

i mean is there some noise/variance that may change too fast for a multimeter readout to capture and display whereas a graphing meter would be necessary for even remote accuracy? or would it be pretty straight forward, plug and play as long as i could get it connected to a multimeter capable of 0.1mV readouts to give me a somewhat accurate readout @ .5umol increments?

if there's not something i'm missing, this may just be the "affordable" answer for the budget aware handy man with limited need and more limited access.

here's the conversion quotes from the online manual for the SQ series for reference...


> All Apogee quantum sensor models have a standard calibration of exactly:
> 5.00 μmol m-2 s-1 per mV


their worked example...


> sensor output * conversion factor = PPF
> 400 mV * 5.00 μmol m-2 s-1 per mV = 2,000 μmol m-2 s-1


i've got a multimeter or two lying around that are capable of such readings. even if not, there's always the possibility of picking one up. pretty sure i could get something in the $60 - $80 range... or is there a reason that may not be advisable when considering it's use in conjunction with the sensor? the meter certainly would get more use than the sensor in my house, that's for sure.

if there is any likely downside that you can think of, by all means let me know.


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## Daximus (Oct 19, 2011)

Naekuh said:


> Meh reading vendors site its says your right..


For the record...Hoppy is pretty much always right, lol


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## Naekuh (Oct 19, 2011)

Daximus said:


> For the record...Hoppy is pretty much always right, lol


lulz... i agree... hoppy is typically correct.. :icon_mrgr


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## Hoppy (Dec 24, 2005)

Naekuh said:


> lulz... i agree... hoppy is typically correct.. :icon_mrgr


I'm just good at hiding my mistakes.:icon_mrgr


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## DKRST (Jan 20, 2011)

Only question I'd have is regarding the sensor being well-sealed against water, both the sensor and the sensor cable connection (and I have not looked at the sensor specs, so this is idle speculation). Other than that, it's certainly cost-effective!


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## Hoppy (Dec 24, 2005)

It's the same sensor, which is very waterproof.


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## dundadundun (Apr 8, 2010)

que no gusto? Lo siento.

hoping to hear back from apogee about my questions some time this week.


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## dundadundun (Apr 8, 2010)

my inquiry...



> To: tech support
> Subject: sq sensor inquiry
> 
> 
> ...


the response...


> my name,
> 
> 
> 
> ...


so if you have a multimeter that can read .1mV than you can have an accuracy of .5 μmol using just the SQ-120 sensor for your tanks.

with a little searching, there shouldn't be a problem getting a multimeter capable of such measurements for under $80 if you don't already have one.


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## Optix (May 31, 2011)

^please start a thread if you go this route

some simple math could mean $100 savings


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## dundadundun (Apr 8, 2010)

^^^ $160 for folks like me that already have a capable multimeter, solder, spare banana plugs and shrink tube to fasten the three wires into two acceptable plugs for the meter.

it only makes sense to utilize this option as a tool to bring quantum meters to the hobbyist level. the difference in price is all but too obvious and oft times a deal breaker when weighing the options of another tank, co2 system, priorities, etc..

we already know folks don't mind getting their hands deep into diy. this is a pretty simple diy with the potential of a $160 savings. that's pretty significant considering the MQ models run @ ~$300. over 50%.

unfortunately, i won't be doing this for some time, personally. finances will not allow it. if all goes well, maybe tax season. maybe not, though.

in light of the situation and since you asked and i cannot provide without product, here's a thread with a couple pics of the multimeter par meter with an sq-110. wrong choice of sensor since the 110 is calibrated for sunlight and 120 is for electrical lighting input, but the principle is illustrated simply in the photos that remain... http://www.cvreefers.org/showthread.php?17167-Bought-an-Apogee-Quantum-SQ-110-sun-par-meter

one thing i would do different is splice the silver wire with the black wire to keep it connected, but that may very well be just semantics.

i also found out the degradation of calibration of the unit seem to be highly dependent on the amount of light it receives over the course of time per this post here... http://www.barrreport.com/showthread.php/9278-PAR-Meter-Question?p=74392#post74392

i've got an old algae scraper laying around from before i started using credit cards for scraping i can drill a hole in to mount the sensor head to also. throw a couple zip ties on there and call it a day. another $50 pocketed.

i'd love to see this be more the recommended avenue for price alone. would be much less discouraging.


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## redfishsc (Aug 29, 2010)

dundadundun said:


> with a little searching, there shouldn't be a problem getting a multimeter capable of such measurements for under $80 if you don't already have one.


My Radio Shack digital meter ($30) claims to be able to read at LEAST 1 mV but it may claim to read lower than that. 

I have no idea how reliable that is though. I'd buy a PAR meter sensor at some point if I could verify my multimeter, but not until then lol....


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## dundadundun (Apr 8, 2010)

redfishsc said:


> My Radio Shack digital meter ($30) claims to be able to read at LEAST 1 mV but it may claim to read lower than that.
> 
> I have no idea how reliable that is though. I'd buy a PAR meter sensor at some point if I could verify my multimeter, but not until then lol....


easy test to see to what decimal it will read on mV...

plug the + lead into +dc and plug the - lead into ground. 
turn that bad boy to the lowest dc V setting and put both leads very close, and pinch them with the same fingers. the readings will jump all over the place and expose the lowest possible decimal place on a reading.

then you'll know if your meter is capable of .5 or 5 umol accuracy.

you still have to factor a percentage in for the meter and the sensor for best accuracy, but if you're ok with the decimal place, that's only minor.


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## redfishsc (Aug 29, 2010)

Well yeah that's obvious lol, I just have to dig it out to see. 

However what I'm wondering how to test it to see if it's actually accurate.


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## Hoppy (Dec 24, 2005)

redfishsc said:


> Well yeah that's obvious lol, I just have to dig it out to see.
> 
> However what I'm wondering how to test it to see if it's actually accurate.


When we first started playing with the Quantum PAR meter, Tom Barr got a known extremely accurate PAR meter and compared its readings to the Quantum meter. They were near enough to being exactly the same for him to conclude that the Quantum meter was very accurate. So, to check your MVmeter/Quantum sensor combination for accuracy you could get ahold of a Quantum PAR meter do the same thing. Otherwise you can only assume the MVmeter/Quantum sensor is equally accurate. And for our purposes, that should be good enough anyway.

It might even be more accurate for PAR below 20 micromols or so. Remember, the Quantum meter only indicates in whole numbers - no decimals. That means a reading of 5 micromols is only accurate to +/-0.5 micromols, or +/- 10%. If your MVmeter reads in decimals, it should be more accurate than that.


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## redfishsc (Aug 29, 2010)

Hoppy said:


> When we first started playing with the Quantum PAR meter, Tom Barr got a known extremely accurate PAR meter and compared its readings to the Quantum meter. They were near enough to being exactly the same for him to conclude that the Quantum meter was very accurate. So, to check your MVmeter/Quantum sensor combination for accuracy you could get ahold of a Quantum PAR meter do the same thing. Otherwise you can only assume the MVmeter/Quantum sensor is equally accurate. And for our purposes, that should be good enough anyway.
> 
> It might even be more accurate for PAR below 20 micromols or so. Remember, the Quantum meter only indicates in whole numbers - no decimals. That means a reading of 5 micromols is only accurate to +/-0.5 micromols, or +/- 10%. If your MVmeter reads in decimals, it should be more accurate than that.


Yeah I got a chance to play around with a Licor PAR meter once--- awesome meter. 

Using another PAR meter to test is a good idea but it requires that I buy the sensor first lol and I'd hate to buy the sensor and then find out I still have to buy another millivolt meter in case mine isn't accurate enough. 


By the way, I ran across this the other day. It's actually more useful than a PAR meter and cheaper. $160-180. 

http://reefbuilders.com/2011/08/21/seneye-unboxed/


The Seneye Reef monitor. Here's the quote from ReefBuilders (this would work just fine in a planted tank btw).


Literally it's an emergency monitor but also has a PAR and Kelvin reading built into it. Just plug it into your PC to get the data (or get the wireless version coming out later that loads data to a cloud service).

I'm interested in knowing just how accurate this is compared to a legit PAR meter. My guess is they are using the same basic sensor technology and thus it's pretty accurate. 



> Seneye Reef measurement range
> 
> free ammonia (NH3) * (0 – 0,500ppm)
> pH * (6,5 – 9,0)
> ...


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## dundadundun (Apr 8, 2010)

redfishsc said:


> Well yeah that's obvious lol, I just have to dig it out to see.
> 
> However what I'm wondering how to test it to see if it's actually accurate.


it's only a voltmeter, you'll be using, so you can just test it on a range of applications. wall socket, car battery, remote battery, 2 remote batteries in series, car alternator (turn car on and put leads on battery), etc.

if all seems to check out and looks ok, the low end of the meter calibration shouldn't be too iffy. basically... for the most part, when they're off, they're off noticeably or at least within their given range (+/- _._ %). it's likely you can look up your model# and find the %accuracy range.

the absolute accuracy of the sensor is already +/-5%. even a $20 multimeter commonly has a rated accuracy of ~0.5% @ 100 uV resolution... if it's capable of such a resolution. there's a multimeter going for $19.99 on amazon right now labeled as "L:AC/DC Digital MultiTesters Multimeter Hand Tool Meter". if you do a search for that and check out the stats, you'll see what i'm talking about.

a better voltmeter isn't going to amount to an overwhelming increase in accuracy. the type of light you're reading and how you account for that would be much more beneficial considering the ~10% apparent difference between sun and electrical lighting calibration between units. 5% and 10% discrepancies are massive in comparison to any digital multimeter that i'm aware of.

example: assuming the light you're testing results in perfect measurements per your units calibration...

say your reading comes out to 20 umols (4mV exactly)

+/-5% for the sensor = 19 - 21 umols (3.8mV - 4.2mV)

+/-0.5% for the cheapy voltmeter = 18.905 - 21.105 umols (3.708mV - 4.221mV)

as far as the security doohickey, i'd be more interested to see how they treat the U.S. market and how the product fares/works. it seems to be more of a continual use item which would significantly increase degradation in comparison to a unit stored in a cool, dark place until it's needed for use. this would incur an increase of ownership cost that seems to me would negate the initial savings in short order. i'd be curious to its usefulness when utilized as an intermittent use device. turn it on, gather my data, turn it off and put it away until next use, etc.. i notice it mentions hourly data recording. i'd be curious if that's an hours worth of data or a single point recorded every hour. i see no display, either. that seems like a hassle when attempting to gather data sets for different regions of the tank. i'd hate to e forced to go back and forth from my tank to my pc to keep uploading data from each zone. seems a recipe for disaster.


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## Hoppy (Dec 24, 2005)

It has always been gospel that there is no way to use a lux meter in place of a PAR meter. And, I always accepted that as the truth. Now, I disagree, to some extent. If you want to limit your measuring of PAR to measuring it in the air, not in the water, you can use a lux meter and get a usable measure of PAR. There is no single conversion factor that will convert lux to micromols per square meter per second (PAR), because PAR is a measurement of the total energy of the photons striking the surface, and the energy per photon varies with the wave length of the light. But, we use a very limited variety of light sources, all of which are similar, since we are lighting an aquarium and want a specific appearance of the tank. The conversion "constant" from lux to micromols for cool white fluorescent light is about .014, and that is also the conversion factor for MH light, so it has to be pretty close for all white planted tank lights.

Ebay now has listings for $20- $40 luxmeters with adequate accuracy for our uses. The sensor is clearly not waterproof, so it couldn't be used in a tank of water, but it could be used very effectively for measurements in air. We know that the PAR in air will read low compared to the same light in the water, by around 15%. That makes these meters a useful tool, for determining how high to hang a specific light above a tank, for how much current to use on DIY LED lights, what wattage CFL bulbs to use, etc.


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## Quaid (Apr 14, 2009)

My lab uses the QSL2100 from:
http://www.biospherical.com/
The wand is submersible (yay) but our PAR radiometer is an older model that needs legacy hardware adapters to connect to modern computers (darn). The company does sell the newer "AMOUR USB" for anyone looking for something modern and more professional than the Apogee or similar aquarium hobby PAR radiometers.


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## Hoppy (Dec 24, 2005)

If all you are trying to do is make sure you are providing a good level of light for a planted tank, you don't need extreme accuracy. If you can determine that you have somewhere between about 20 and 30 micromols of PAR at the substrate you can treat the tank as a low light tank. If you also have the light hanging about one tank height above the top of the tank, you can be sure you don't have extremely high light anywhere in the tank. For a tank with CO2, if you can determine that the PAR at the substrate is between about 40 and 60 micromols of PAR you should be able to grow anything, and not be faced with extreme algae infestations. And, again, if that is with a light hanging one tank height above the top of the tank, the PAR near the top of the water will not be so extreme as to cause constant algae attacks. Determining that the PAR is within those ranges doesn't take much accuracy.


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## firefiend (Sep 3, 2009)

Thanks for all the feedback, everyone. So for my situation, where I have 1 10 gallon (which is giving me tons of problems); a 5 gallon and a 1 gallon and a 55 gallon waiting for summer. Can I get buy with just the air measurements? and then extrapolate the 15% water effect?

I don't want to short change the quality of the PAR(or Lux) meter because I am interested in learning all the aspects of the hobby; however, with the financial limitiations I would like to be able to put as much money toward setting up the 55 as possible.

So, for general purposes of setting up tanks and then troubleshooting lighting issues, will a lux meter suffice?


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## Hoppy (Dec 24, 2005)

If you want to measure how much PAR is in every corner of your tank, how much is getting through the vals draped across the top, how much is getting through the floating plants, how much is getting by the stem plants to the ground cover, etc., you have to use a PAR meter or at least a lux meter with a waterproof sensor. But, if you want to know how much light you can get at the substrate level with your hydroponics T5 light and DIY reflectors, a lux meter will work fine. You can just adjust the numbers to account for the amplifying effect of having water in the tank, and use a general conversion constant to convert from lux to PAR units. It all depends on how you plan to use the meter.


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## mistergreen (Dec 9, 2006)

Make sure to get an electronic voltmeter. It's more sensitive through amplification, about 10% more accurate.


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## firefiend (Sep 3, 2009)

Hoppy said:


> If you want to measure how much PAR is in every corner of your tank, how much is getting through the vals draped across the top, how much is getting through the floating plants, how much is getting by the stem plants to the ground cover, etc., you have to use a PAR meter or at least a lux meter with a waterproof sensor.



Ultimately, to get a full understand of my tanks, I think I would need this capability. The trick is to do it as affordably as possible. It seems that lux meters are a bit less expensive but then I need to buy waterproof sensor.

and now I'm confused between PAR, Lux and electronic voltometer.


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