UV/ Light sensor window. Fused silica and other options.

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Grumpf
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UV/ Light sensor window. Fused silica and other options.

#1 Post by Grumpf » 18 Sep 2020, 15:55

First, sorry if it's the wrong section. I couldn't find the answer in the forum already.

Got a lot of nice working sensors for light like :

TLS2561
GY1145
GYML8511
BH1750

And to some extent :

MLX90614
TCS34725

Question is, circuit is working fine, everything's ready for production but what now of the enclosure ? I need light to go to the sensor unaltered.

I've seen that : https://shop.switchdoc.com/products/dou ... -30-30-1mm
2020-09-18 15_53_28-Double Side Polished Far-UV Fused Silica Quartz Glass Sheets Plate 30_ – SwitchD.png
2020-09-18 15_53_28-Double Side Polished Far-UV Fused Silica Quartz Glass Sheets Plate 30_ – SwitchD.png (166.23 KiB) Viewed 14854 times
But do I need it or some plastic can do ? Do you guys have any experience with it ?

Cheers,
Grumpf.

Ton_vN
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Re: UV/ Light sensor window. Fused silica and other options.

#2 Post by Ton_vN » 20 Sep 2020, 11:24

The setup described here (in Dutch) is used to house a set of 2*TLS2561 + 1*ML8511:
the sensors look with slight vertical offset of approx. +30 degrees through a window made of a plastic document cover and plastic gaze.
Considering UV & ML8511 first only a gaze window, but experienced that the plastic document cover had almost no effect (and ;-) is better protection against the weather.

Have also in operation SI1145 and GUVA-S12D each in a white-glass bowl lampholder, and was surprised how little effect that glass has on the UV-reading by these sensors:
see related (dutch) description.
Also MAX44009 is a clear, plastic bowl lampholder.

;-) Just luck, or are we too much worried about attenuation for UV?
Anyway, you must bear in mind that data from such sensors is as good as the calibration of the setup, regardless of any interfering effects of objects in the vicinity.
Last edited by Ton_vN on 20 Sep 2020, 14:43, edited 1 time in total.

TD-er
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Re: UV/ Light sensor window. Fused silica and other options.

#3 Post by TD-er » 20 Sep 2020, 11:41

Usually ShardanX is the one with the most experience in how materials behave and really insightful replies.
But as he hasn't replied yet, so maybe I can also put in my 2 cents here.

When using plastics, you may risk the UV breaks apart the compound that keep plastic flexible ("weekmakers" in Dutch, not sure about the English term, maybe "plasticisers" ?)
So after a while plastic may form cracks or break easier on impact (e.g. in a hail storm).

Ton_vN
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Re: UV/ Light sensor window. Fused silica and other options.

#4 Post by Ton_vN » 20 Sep 2020, 14:35

@TDer

'Softener' seems the word you look for.

My experience on this subject comes from professional application of optronics in open air (maritime environment).
;-) Home application in my garden certainly is a different class, considering the trade-off between cost & quality; but the experience counts.

The sheets found by Grumpf surely are for application for sensing far-UV:
he only must invent a holder keeping such sheet in front of the sensor, covering the whole field of view of the sensor.
Would be useful if the transfer characteristics of the sheets could be mentioned [= range bracket of wavelength and related attenuation]

My (home) aim is to apply easily available materials, simple & sturdy and easily replacable.
Main concern is compatibility in wavelength and life-cycle.

Plastic sheet covers for home application should be thin and uniform:
the thinner, the better for transfer of light of all types, but on the other hand the sheet should be thick enough to survive for some time.
(Dutch) bags for bread are nicely thin, but e.g. document holder front covers seem a better compromise, lasting longer in dutch weather.
A crack or split causes disruption of the light transmission, and dictates replacement.
Discoloring may occur when heated or long subject to UV.
Coverage by some salt usually is not a real problem, but a unequal layer of dust is 'not good'.
Plastic gaze cover of white/transparant variety is better transparent for all kinds of light.
By it's structure it usually fends off raindrops etc. (=> the grid must be very small)
Cleaning of sheet or gaze is not trivial: replacement usually is easier and more effective.
Both materials deteriorate under the influence of UV & temperature and become brittle (due to those 'softeners' loosing their characteristics).

The white-glass and clear-plastic bowl lampholders were a pleasant surprise, in practise having good transmissien for light and for UV.
On the other hand the lack of ventilation inside the bowls is 'killing' during sunny periods:
the electronics do not like the resulting very high temperatures and ultimately will 'strike'.

Demonstration that configuration matters is also by the plastic dome coming with my zenith scanning BH1750:
as construction it looks nice, but very clear attenuation for incoming light, when comparing with performance of another 'naked' BH1750.
The experiments with that domed BH1750 also demonstrated another aspect:
the location at the top of the hood of a ventilation exhaust as housing was excellent spot for measurement, well protecting against falling rain, but the air circulating in the housing & head induced condensation at the underside of the hood, which was killing for the electronics of that BH1750.
;-) Lessons learned by practise .....
Ventilation exhaust aka Lighthouse
Ventilation exhaust aka Lighthouse
Lichtmeethuis.jpg (79.53 KiB) Viewed 14742 times
Domed BH1750
Domed BH1750
bh1750dome.jpg (43.83 KiB) Viewed 14742 times
Last edited by Ton_vN on 22 Sep 2020, 17:48, edited 4 times in total.

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Grumpf
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Re: UV/ Light sensor window. Fused silica and other options.

#5 Post by Grumpf » 21 Sep 2020, 10:31

Thanks guys, I'll experiment a bit with different materials vs no cover at all while it's still nice here. Mmm let's see if I have tow sensors so I can run them in //.

Thanks,

Grumpf.

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Re: UV/ Light sensor window. Fused silica and other options.

#6 Post by Grumpf » 30 Sep 2020, 20:18

I asked a friend to give me a disposable UV cuvette used in lab for spectrophotometry. I'll keep you posted on my results. Cheers.
IMG_20200928_110847.jpg
IMG_20200928_110847.jpg (199.81 KiB) Viewed 14606 times
ihwx.43f56701-e080-4102-bd10-5f81ce2a81f3.500.500.jpg
ihwx.43f56701-e080-4102-bd10-5f81ce2a81f3.500.500.jpg (19.08 KiB) Viewed 14606 times

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