[werk_ag]

To cover the sensors, I will suggest the use Quartz Fused Silica Glass. Its not a cheap material but a small piece isn't too expensive.
Among the easily available materials I thing it have the best UV transmission, and doesn't cut much light which is very important for both sensors to work properly with the hardware and software.
PTFE will cut too much light, don't use it on top of the mini solar panel.

Product:UV Grade Fused Silica Quartz Glass
Type:JGS1
Diameter:75mm
Thickness:2.0mm

I am quite happy with that. The met office said a high of 1 for UV.
I will keep monitoring the results but seeing that the solar panel cost about £5 and the UV sensor was also about £5 I am not expecting super accuracy.

That is an important point. When comparing with a Davis or Apogee instruments (I have two Apogee SP-110) the results are quite similar, by a fraction of the price.

...
or a true UVB sensor such as the VEML6075 (which has sadly got quite expensive now).

WeatherDuino also supports the VEML6075. Indeed, as AllyCat said, currently it is quite expensive (around 20€ at AliExpress), but seems a good UVB sensor (it provides readings of both UVA and UVB, then some math on the library returns the UV Index).
As a side note, the reason why the 4Pro TX have two extended I2C ports, is to use one for the T/H sensor, and the other for another I2C sensor, like the VEML6075 (normally both aren't placed on the same place, which will require two independent cables).
Of course the second half of the extended I2C circuit (two pcb's are supplied) must be on the side of the sensors.

[SR123]

.....continued

After a few weeks of 'Testing' I have now set up the Transmitter outside and have migrated the new system to the 'working' Cumulus MX. I have also managed to get hold of a second hand 'Brand New' Davis 6410 wind speed/direction sensor at a bargain price I will install that shortly in place of the old fine offset one

Picture of completed Tx in its waterproof box

   

Picture of location of sensors (wind sensors are on the gable end of the house)

   

Picture of the antenna I made for the Tx, it's a quarter wave dipole made from copper pipe - seems to work well.

   

Thanks for looking.

[hornychz]

 Congratulations!

[SR123]

I have been very happy with my system, it's been performing really well - I have changed the old fine offset wind sensors for a Davis 6410 and I managed to get hold of a 'new in box' Davis rain gauge (7852) for an Ebay bargain of £26 delivered!

Anyway, Today I decided to try different materials to cover my solar & uv sensor. I have been using 3mm Perspex but even on really clear sunny days the uv readings have never been more than 1.
The tests I performed Today was as follows, the Day started with clear blue skies but became hazier in the afternoon.
I removed the original 3mm perspex at 10:30 and left the sensors uncovered for 30 mins, I then covered the sensors with 1mm thick PTFE for 30 mins, then every 30 mins I changed the cover for anything I could find that was clear! 2mm 'picture frame' glass, then 2mm clear plastic - not sure what it is, it was from a box lid, then I left it uncovered again, 3mm glass from a greenhouse, then I put the 3mm perspex back on again, finally put the 3mm glass back on.

   

As can be seen quite interesting. Now for the questions
From the (not very scientific) results 3mm perspex or 1mm PTFE is no good for uv! but everything else seemed ok, however, the uv readings seem way too high! the met office forecast a max uv of 5 and I was getting a reading of 10! Is there a way to calibrate the sensor? What are the variable resistors RV1 and RV3 for?

Thanks, Steve

[werk_ag]

....
What are the variable resistors RV1 and RV3 for?

Thanks, Steve

Hi Steve,

In very good to know that you are happy with your new WeatherDuino weather station.
Interesting experiments...

The variable resistors RV1 and RV2 / RV3 are used to set the gain of the two channels of the OP IC5.

- RV1 sets the gain of the channel used for Solar Radiation. If you are using our Photovoltaic Cell, its value should be set to around 2.7K (may be fine tuned).

- RV2 / RV3 are used for the UV channel. We only have tested the system with the UVM-30A UV sensor, but it should work with any sensor with a linear response between output voltage and the UV Index. In any case, the maximum output voltage of the sensor should not exceed than 1.1V.
UVM-30A UV sensor set RV2 to 10K and RV3 to 0 (Zero or as near as possible). Purpose is having a gain = 1, when using the UVM-30A UV sensor.

If you have access to a little piece of Fused Silica glass try it, I think its the best material to use as cover for the kind of UV sensors we are talking about (covering the Photovoltaic Cell with Fused Silica glass also doesn't have any negative impact on the readings).

Rgs.

[SR123]

Thanks for the info - I am now confused

I set my RV2 and RV3 according to the 4Pro Universal Transmitter - General Usage & Assembling Guide

1.2 Measuring UV Index
Instructions below apply when using the UVM-30A UV sensor.

RV2 = Adjust to maximum value (10K Ohm)
RV3 = Adjust to minimum value (0 - 100 Ohm)


Now you are saying,
RV2 = 0 K Ohm
RV3 = 1-2K Ohm

Could you please clarify?

Thanks, Steve

[werk_ag]

Hi Steve,

Sorry for my mistake on the last post, the correct instructions are the ones posted on the 4Pro Universal Transmitter - General Usage & Assembling Guide

1.2 Measuring UV Index
Instructions below apply when using the UVM-30A UV sensor.

RV2 = Adjust to maximum value (10K Ohm)
RV3 = Adjust to minimum value (0 - 100 Ohm)

I will correct my mistake on last post to avoid confusion for other users.

Once again, my apologies.

Rgs.
Werk_AG

[SR123]

Thanks for clearing that up

Today I recorded a maximum UV of 7, which is too high. The maximum should have been 5.
What would you recommend I do?

Thanks, Steve

[werk_ag]

Thanks for clearing that up

Today I recorded a maximum UV of 7, which is too high. The maximum should have been 5.
What would you recommend I do?

Thanks, Steve

Hi,

According to specs, the UVM-30A tolerance is +- 1UV Index.
You can also try to do some adjustments on the software side.

On the receiver software, RX_TX tab, find this code (around line 360) :

Code:

#if (UV_SENSOR == 1) // --- UVM-30A
IndiceUV = ((RX_Data[2] * 12.0 * (100.0 / UV_Transmission)) / 1024.0);
#endif

Try lower the "12.0" value.

Rgs.
Werk_AG

[Nigel]

Hi SR123,

I've really enjoyed reading about your Stn.  It's given me some ideas.  I do like what you have done with your RX been thinking about what to do with my own.  Looks like some bits of roofing batten (38 x 50 mm) might come in useful...  Though I have been thinking of something else.  I was intrigued by the strainer that you mounted your T/H sensor in.  I too have been using a FO system for a number of years and having replaced a number of parts / whole lot have decided to abandon FO.  When I inspected the TX over winter break it was badly corroded and I do what to protect the sensor more than in the FO set up.  I have retained the radiation screen and have been thinking of ways to use this with additional protection for the little PCBs.  I have some "conformal coating" to put on the PCBs (except the sensors that is).  I might emulate your strainer screen though I have been thinking about a tube inside the radiation screen...

I've gone for a bought antena both TX and RX and will keep the TX one in the IP enclosure so as to minimise holes in the enclosure (though conversely I plan to have the indicator LEDs visible in the side of the enclosure!!!).

I've not have the solar data before so am only just giving it some thought.  As Werk is saying fused silica is the best for UV transmission it is used in UV reactors for disinfection of water.  Despite being surrounded by United Utilities and Yorkshire Water reservoirs my house is on a private water supply!

Stay safe

Nigel