Par meters

Rahz

Rahz

Well-Known Member
A quick search shows them available anywhere from $75 to $300.

A quick search for spectroradiometers shows them available anywhere from $1700 to $25000.

I don't have the cash to plunk down on a spectroradiometer, but what I'm mostly interested in is a comparative analysis between the DIY builds I've built and will build -vs- some of the commercially available lamps that publish par footprints.

So my question has to do with the equipment used to produce such maps and what I would need to buy to create reasonable comparisons. Will a $75 unit do the job? Will a $300 unit produce more accurate results?
 
Abiqua

Abiqua

Well-Known Member
This one is pretty good comparing the Apogee, the Scout and the Li-Cor.....compared to the Li-cor, other two are bargains, but the Li-cor seems to be more consistent across the PAR spectrum for its analysis...

http://www.advancedaquarist.com/2013/2/equipment

This guy built his own and then calibrated to an Apogee before using:
http://www.plantedtank.net/forums/showthread.php?t=120109


Form your own conclusions, there seems to some trouble with the "ends" of the spectrum and few silicon photodiodes are up to the task.....so far, a little clipping of blue and far red....:peace:
 
Abiqua

Abiqua

Well-Known Member
I have seen someone build a integrating sphere? from a painted tennis ball, that seemed to work....google it.... I will dig around in my links....
 
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alesh

alesh

Well-Known Member
Abiqua said:
I have seen someone build a spectroradiometer from a painted tennis ball, that seemed to work....google it.... I will dig around in my links....
Click to expand...
You mean an integrating sphere, don't you? Two different things. For our purposes it'd be ideal to have both but these are expensive toys. DIY is not exactly easy way there, too.
 
Abiqua

Abiqua

Well-Known Member
alesh said:
You mean an integrating sphere, don't you? Two different things. For our purposes it'd be ideal to have both but these are expensive toys. DIY is not exactly easy way there, too.
Click to expand...
yes yes, I strayed my apologies....
 
AquariusPanta

AquariusPanta

Well-Known Member
alesh said:
No need to. I'm sometimes a little pedant about terms but only to prevent confusion. We are seeing it there every day.

Those interested in (DIY) integrating spheres and more, don't miss candlepowerforums.com.
Click to expand...
Haha, he said candlepower.

:lol:
 
captainmorgan

captainmorgan

Well-Known Member
You can buy just the sensor and use a MM to read it.

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




How can I use a voltmeter to determine readings from my quantum sensor?

The SQ-100 and 300 series are considered to be self-powered and have been calibrated to 5.0 µmol m-2 s-1 per mV. Use a voltmeter with a mV setting to attain better resolution. Connect the positive lead of the voltmeter to the red wire of the SQ and the negative lead of the voltmeter to the black wire of the SQ. Once you are reading the mV output from the sensor, simply multiply this reading by 5.0. This will give you the µmol m-2 s-1 output from the sensor, otherwise known as Photosynthetic Photon Flux (PPF) or Photosynthetically Active Radiation (PAR).
 
Abiqua

Abiqua

Well-Known Member
alesh said:
No need to. I'm sometimes a little pedant about terms but only to prevent confusion. We are seeing it there every day.

Those interested in (DIY) integrating spheres and more, don't miss candlepowerforums.com.
Click to expand...
churchhaze said:
Make a voltage divider with a cheap photocell, and use a multimeter to get a readout. 20 cent PAR meter.

Click to expand...
Then something to cut UV/IR.....problem is with most of these LDR's especially the cheaper ones, is they skew toward 850nm [or higher] as their peak....where the Excelitas I have my eye on, is like 680nm I think...quite drastic in $5 diodes...wouldn't you need a good op amp for better readings or is the op amp only for A/D conversion?....I wouldn't think they would be precise enough to matter....
I wish I had a more thorough understanding of analyzing circuits, like I think you have Church, care to elaborate more....thanks!

Also this too....DIY Par Meter 2015 from RC
http://www.plantedtank.net/forums/showthread.php?t=823705
 
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PSUAGRO.

PSUAGRO.

Well-Known Member
captainmorgan said:
You can buy just the sensor and use a MM to read it.

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


How can I use a voltmeter to determine readings from my quantum sensor?

The SQ-100 and 300 series are considered to be self-powered and have been calibrated to 5.0 µmol m-2 s-1 per mV. Use a voltmeter with a mV setting to attain better resolution. Connect the positive lead of the voltmeter to the red wire of the SQ and the negative lead of the voltmeter to the black wire of the SQ. Once you are reading the mV output from the sensor, simply multiply this reading by 5.0. This will give you the µmol m-2 s-1 output from the sensor, otherwise known as Photosynthetic Photon Flux (PPF) or Photosynthetically Active Radiation (PAR).
Click to expand...
remember that guod said NOT to skimp on the MM for this to be somewhat accurate..........still won't play nice around DR and beyond
 
A

az2000

Well-Known Member
Rahz said:
I don't have the cash to plunk down on a spectroradiometer,
Click to expand...
Take a look at the DIY spectrometer from PublicLabs. It costs about $40 and it's fun. I get good results, comparing lights, etc.

I have the "desktop" model. It's instructions weren't adequate. Some things I did to make it better:

1. Spray paint the interior flat black to reduce reflections. (You can do better with special light absorbing paint or felt, but Rustoleum flat black seemed good enough.).
2. Epoxy the camera onto the wood. The double-sided tape comes loose.
3. Drill a hole to use a woodscrew to hold the wood. (Same reason.).
4. Focus the camera on a point where the slit/aperature is. (You'll have to measure that distance, then focus outside the enclosure to that distance. Lens has a small red handle to turn it.).
5. Remove the plastic film over the lens. Not sure if this is an IR filter or just protective (and a handle to focus).
6. Epoxy a nut on the bottom for a tripod to screw onto.
7. May need photographic filters to reduce a light's intensity. I've read light reflected off a white poster board. But, there's a risk the posterboard will add it's own color. I've tried creating a second slit using electrical tape. That works to some extent. But, sometimes you really need to cut it down more. They have some kind of laser-cut slit they sell as an add-on.

You use their online "workbench" tool. You calibrate to a CFL which apparently has a mercury vapor signature consistent to all CFLs. You can capture, save and download data to use in a spreadsheet (to chart however you wish).

The online tool has some quirks too. The most important is that it lets you see the exposure either in RGB or combined. The problem is, if you look at it combined, any of the three colors can be overexposed and clipped. You'd see that if looking at RGB lines. But, when looking at combined, it doesn't tell you that. It just alters the combined line using the clipped input. You need to capture in RGB, then view the capture in combined.

I've looked at Cree diodes and the curve I get is close to what Cree's datasheet publishes. The scale is off. Once you load it into a spreadsheet and scale it similarly, it's close.
 
Abiqua

Abiqua

Well-Known Member
az2000 said:
Take a look at the DIY spectrometer from PublicLabs. It costs about $40 and it's fun. I get good results, comparing lights, etc.

I have the "desktop" model. It's instructions weren't adequate. Some things I did to make it better:

1. Spray paint the interior flat black to reduce reflections. (You can do better with special light absorbing paint or felt, but Rustoleum flat black seemed good enough.).
2. Epoxy the camera onto the wood. The double-sided tape comes loose.
3. Drill a hole to use a woodscrew to hold the wood. (Same reason.).
4. Focus the camera on a point where the slit/aperature is. (You'll have to measure that distance, then focus outside the enclosure to that distance. Lens has a small red handle to turn it.).
5. Remove the plastic film over the lens. Not sure if this is an IR filter or just protective (and a handle to focus).
6. Epoxy a nut on the bottom for a tripod to screw onto.
7. May need photographic filters to reduce a light's intensity. I've read light reflected off a white poster board. But, there's a risk the posterboard will add it's own color. I've tried creating a second slit using electrical tape. That works to some extent. But, sometimes you really need to cut it down more. They have some kind of laser-cut slit they sell as an add-on.

You use their online "workbench" tool. You calibrate to a CFL which apparently has a mercury vapor signature consistent to all CFLs. You can capture, save and download data to use in a spreadsheet (to chart however you wish).

The online tool has some quirks too. The most important is that it lets you see the exposure either in RGB or combined. The problem is, if you look at it combined, any of the three colors can be overexposed and clipped. You'd see that if looking at RGB lines. But, when looking at combined, it doesn't tell you that. It just alters the combined line using the clipped input. You need to capture in RGB, then view the capture in combined.

I've looked at Cree diodes and the curve I get is close to what Cree's datasheet publishes. The scale is off. Once you load it into a spreadsheet and scale it similarly, it's close.
Click to expand...

You know what this would really work good for....entry level aluminum / barium detection in the atmosphere...and if you already have a webcam, I think you can build this for less than $10 :peace
 
Rahz

Rahz

Well-Known Member
I'm mostly interested in light intensity, although I do have an interest in DIY I have my hands full with various hobbies and work. I'm thinking it might be best to get a sub $100 par meter to play with for the time being. It would at least let me examine footprints and compare various LEDs against one another. I'm not sure how reliable they would be comparing LED to HPS, but then again I'm not sure how well a $300 unit like the Apogee would work in that regard. Couple comments I've read:

Why spend that much on it? It's basically just a lux meter that does a conversion.

They can be off by up to %30 (I think this comment may have been in regard to measuring specific wavelengths)

For white light, just add 10-15% for a more accurate estimate.

Obviously adding some numbers on top of a shaky measurement isn't going to be good data, but again I'm just wanting some comparative results and to check intensities in a footprint. So... why not get a $75 meter?
 
C

churchhaze

Well-Known Member
Abiqua said:
Then something to cut UV/IR.....problem is with most of these LDR's especially the cheaper ones, is they skew toward 850nm [or higher] as their peak....where the Excelitas I have my eye on, is like 680nm I think...quite drastic in $5 diodes...wouldn't you need a good op amp for better readings or is the op amp only for A/D conversion?....I wouldn't think they would be precise enough to matter....
I wish I had a more thorough understanding of analyzing circuits, like I think you have Church, care to elaborate more....thanks!

Also this too....DIY Par Meter 2015 from RC
http://www.plantedtank.net/forums/showthread.php?t=823705
Click to expand...


Something like that.
 
Abiqua

Abiqua

Well-Known Member
Rahz said:
I'm mostly interested in light intensity, although I do have an interest in DIY I have my hands full with various hobbies and work. I'm thinking it might be best to get a sub $100 par meter to play with for the time being. It would at least let me examine footprints and compare various LEDs against one another. I'm not sure how reliable they would be comparing LED to HPS, but then again I'm not sure how well a $300 unit like the Apogee would work in that regard. Couple comments I've read:

Why spend that much on it? It's basically just a lux meter that does a conversion.

They can be off by up to %30 (I think this comment may have been in regard to measuring specific wavelengths)

For white light, just add 10-15% for a more accurate estimate.

Obviously adding some numbers on top of a shaky measurement isn't going to be good data, but again I'm just wanting some comparative results and to check intensities in a footprint. So... why not get a $75 meter?
Click to expand...
Why not just get a $15 luxmeter and adjust the photometric data....then if you really want PAR functionality...a Uv/ IR cut will filter above 400nm and below 700m....But that seems to part of the cost of the decent par meter as well, the filter....So now with a filter, you could have a $50 DIY meter, but you would still need another meter to calibrate it off of....or complicated math using a known diode NM.....
 
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