Can’t afford $$$ uvb meter, check this out

[Or_Gro]

Hey dudes, i have one of these to measure and set height on my uvb tubes:

It works great, but price is $$$ for some people. So @chiefrunningphist on riu asked me to buy one of these (free app for i-phone/android), and compare to my meter:

Here is one of crp’s posts explaining his rationale:

I tested it under a single 4’ tube of these:

I let my light warm up for 15 mins, then ran the meters side-by-side, here’s what i got:

Line-of-best-fit (plug target uW/sq cm as “x”, tells you target UV Index value):

[LEDG]

I see you like testing as much as I do!

Thanks for sharing your results.

[Frank Cannon]

LOL you ain't seen anything yet with OverKill and testing

OG, so that looks like a real nice correlation and but I am guessing that this lille gadget would not be able to be used with 6% and 10% bulbs as the measuring range does not go low enough (30uw/cm2 for 6%)? He calculated for me that the 6%ers would need to run full 12 hours to get 13.4KJ/m2

When i was looking at UV Gman mentioned we should aim for around:

Start in the last veg week with 1+1h(beginning and end of the day) and increase to 2+2h when you switch to 12/12h. From end of the stretch or when the plants start to form the 1st trichomes I would increase to 2x 3h and stay with it until the end.
I've used them 8-12" away from the tops and for the whole 12h without getting any trouble. And I found no feelable difference between 6 and 12h cause the daily dose with 6h is already pretty high. At 12" you have around 100μW/cm² guaranteed. With 6h that's 600μW/cm² per day and multiplicated with factor 0,036 that's already 21,6kJ/m² per day! In the .pdf I've added below they have used 6,7 and 13,4kJ/m² and they have found a linear THC increase. With 2-4h the day you would be in the same range.

[Or_Gro]

I see you like testing as much as I do!

Thanks for sharing your results.

I’m a numbers guy...only way to really approach repeatability...in my book...

Please note randomblame’s comments about this device in the following thread: viewtopic.php?f=11&t=4395

Seems the smartphone device is way off on accuracy...may still have some utility if the error is consistent between devices....random has one on order and will check independently...


[on other sites we can “tag” a member in a message (send them an alert, requesting a response), by putting an “@“ in front of their handle, can we do that here? Thx].

[Or_Gro]

LOL you ain't seen anything yet with OverKill and testing

OG, so that looks like a real nice correlation and but I am guessing that this lille gadget would not be able to be used with 6% and 10% bulbs as the measuring range does not go low enough (30uw/cm2 for 6%)? He calculated for me that the 6%ers would need to run full 12 hours to get 13.4KJ/m2

When i was looking at UV Gman mentioned we should aim for around:

Start in the last veg week with 1+1h(beginning and end of the day) and increase to 2+2h when you switch to 12/12h. From end of the stretch or when the plants start to form the 1st trichomes I would increase to 2x 3h and stay with it until the end.
I've used them 8-12" away from the tops and for the whole 12h without getting any trouble. And I found no feelable difference between 6 and 12h cause the daily dose with 6h is already pretty high. At 12" you have around 100μW/cm² guaranteed. With 6h that's 600μW/cm² per day and multiplicated with factor 0,036 that's already 21,6kJ/m² per day! In the .pdf I've added below they have used 6,7 and 13,4kJ/m² and they have found a linear THC increase. With 2-4h the day you would be in the same range.

Yep, couple things:

See my response above, re: rb’s comments...his post shows the device is WAY off...still a chance that this device is useful (if each of them has same error; we’ll see when rb tests his).

Second, if you look at the deltas between readings, the higher intensity is pretty uniform change for each increase in uW/sq cm, but as you go below 300-400 the variation widens, so line of best fit does poorer job at low intensities.

Bottom lines on uvb, for me: use height as dimmer, ramp dosing slowly, going as high as possible until damage is evident, then back down to previous level and hold...try another ramp a week or two later, back off if damage...

You should be good, w 6%, ramping to full lightson...i ramped to 6hrs/day with my 14%ers @22” last grow, without obvious damage.

[Frank Cannon]

I'm at full 12 hours now and everything looks hunky dory so far at 15inches, will get to 12inches as stretch finishes over next coupla weeks.

[Chiefrunningphist]

I've been looking at this for awhile. I'm not sure what to conclude. It seems to be functioning with consistency, so maybe only a calibration is needed. I wonder how recessed the sensor is?

[Or_Gro]

I've been looking at this for awhile. I'm not sure what to conclude. It seems to be functioning with consistency, so maybe only a calibration is needed. I wonder how recessed the sensor is?

Here's a chart at 10cm of a 12% arcadia...
spectrumUVArcadiaD3plus-T5tube.gif

Here's the tables random posted...
Screenshot_20190623-082426.png

According to the tables, at 15cm the arcadia d3 12% should have a differythemal intensity of 100mW/m2 (4.0 UVI × 25mW/m2 = 100mW/m2), that doesn't seem to far off?? The actual is recorded at 1,360mW/m2, so a weighted intensity of 100mW/m2 seems plausible??

Hmm, digging deeper...

It looks like in the 10cm chart that theres roughly about 168μW/cm2 total UVB intensity or 1,680mW/m2.
USER_SCOPED_TEMP_DATA_orca-image--1977829195.jpeg_1561455077393.jpeg
When I do a rough estimation of the differythemal intensity...

average of ~12.5μW/cm2 from 310-320 multiplied by 10nm = ~125μW/cm2

average of 2.5μW/cm2 from 295-310 multiplied by 15nm = ~37.5μW/cm2

1250mW/m2 × 0.05 = ~62.5mW/m2, 375mW/m2 × 0.33 = ~123.75mW/m2
124 + 63 = ~187mW/m2
187mW/m2 ÷ 25mW/m2 = ~7.45UVI

... I get ~187mW/m2 or ~7.45 UVI. That's spot on for the UVI map they post, but this method doesn't scale accordingly. According to this method, at 15cm or 1,360mW/m2, we should be closer to 6.0 UVI which the map doesn't correlate with.
Screenshot_20190623-082909.png

Investigating further...

The table shows a consistent UVB measurement in μW/cm2 ÷ ~34 to realize the UVI.

136μW/cm2 ÷ 34 = 4.0 UVI
100μW/cm2 ÷ 34 = 2.94 UVI
78μW/cm2 ÷ 34 = 2.29 UVI

The map shows a 7.45 UVI at 10cm, but when I multiply 34 by 7.45 UVI, I get ~253μW/cm2. This means an average of 10μW/cm2+ from 295nm - 320nm, looking at the chart we can clearly see at 10cm it's not averaging 10mW/cm2+ from 295nm - 320nm. I'm roughly calculating 168μW/cm2, I doubt I'm that far off.

Maybe I'm just making some silly math errors, if you see them point them out, its late and my brain is a bit fried lol

Chief, my brain’s twisted and i can’t get up...

you, prawn and randomblame need to talk...

[Chiefrunningphist]

Chief, my brain’s twisted and i can’t get up...

you, prawn and randomblame need to talk...

Lol well hopefully they'll see it to comment on it. I don't know how to tag ppl yet :/ Im curious what they'd have to say too.

[Or_Gro]

Chief, my brain’s twisted and i can’t get up...

you, prawn and randomblame need to talk...

Lol well hopefully they'll see it to comment on it. I don't know how to tag ppl yet :/ Im curious what they'd have to say too.

I posted original post on my grow thread, they’ve responded.

Leave a message there, w link to here; or just repost your post there.

Mods working on enabling tags...