Topic: davis solar sensor

[jerryg]

I have been thinking about getting a solar sensor for my station but i am not sure if the info is worth the price. What is the info obtained from the sensor good for? Does it serve a purpose like the other sensor readings? Does anyone use this info?

[d_l]

The solar sensor is primarily used for agricultural purposes and also power input measurements if you have solar electric or hot water panels.

It is probably mostly used to calculate ET rates.  If you have to water a lawn or garden, that can be useful info.

It also feeds into the THSW (Temp-Hum-Sol-Wind) index which some people feel is a better measure how hot it feels rather than the Humdity Index.

[Skywatch]

I installed a solar sensor on my VP2 a few weeks ago. Besides solar radiation it's self, this is used to calculate ET (evapotranspiration) and THSW (temp-hum-sun-wind) index. The solar sensor in my opinion is a great addition. Just make shure the sensor's not in a place that has shadows in the morning and evening as these can cut the solar readings off. If you ask me, I'm having fun with mine. It's nice to see how the sun interacts with everything. I'd say yes it's well worth it. The only hassle is siting it. I took a small plastic lid, drilled in where the screws and cable bazel are fed through, and used a small metal pipe to mount it.

[Downlinerz2]

     I recentyl just bought a Solar Sensor as well and am just waiting to have in installed.
I think it is a key meteorological parameter.  Can't wait to get it up and running.
   Mark

[d_l]

Oh! Another thing. With the solar sensor you can estimate or at least get a feel for the cloudiness, eg., heavy overcast vs. scattered cumulus clouds vs. high thin hazy clouds.

[Skywatch]

Oh! Another thing. With the solar sensor you can estimate or at least get a feel for the cloudiness, eg., heavy overcast vs. scattered cumulus clouds vs. high thin hazy clouds.

Ah yes I forgot that one thanx.

 Of course it can be confusing when you have those high cirrus clouds giving high readings. This is stated by the manual and witnessed today. My theory is, the clouds as the thin layer of moisture, the water drops probably act as magnifying glasses. Today I saw a solar spike of 1271 W/M2. Yes there were clouds of all sorts today. Those big low level ones make the solar drop the high thin ones make the solar reading rise. It's fascinating.

[d_l]

Yes. If parts of the cirrus clouds are a little "dense", you get a radiation drop, but once the wispy, hazy edges pass in front of the sun, then you get that spike above the normal radiation levels.

[C5250]

Does anyone use this info?

If you are sending data to CWOP, it is one of the parameters collected.

[Skywatch]

Does anyone use this info?

If you are sending data to CWOP, it is one of the parameters collected.

Question, I don't yet have my VP2 W solar sensor working with the computer, CWOP, WU or anything. My WMR100 is a filler untill I can get WL for my VP2. But After paying attention to several stations in my area, a few stations reporting solar to WU. The solar doesn't show up on CWOP (APRSWXNET). Is there a special software program to exporting solar data to CWOP? If so, when I get WL it's going to be in first considerations.

[C5250]

The solar doesn't show up on CWOP (APRSWXNET). Is there a special software program to exporting solar data to CWOP? If so, when I get WL it's going to be in first considerations.

I'm not sure what you are asking... I believe WL sends solar data to CWOP, as do others. I have next to no knowledge of what programs do, and those that don't.

Solar data does not show up on the Gladstone pages, nor on FindU, unless you look at the raw data. But it is ingested by MADIS. This is my raw data on FindU: http://www.findu.com/cgi-bin/raw.cgi?call=CW5250
at the tail end of the string, before the software ID, is a capital L (L = Luminance) followed by a number, that is the solar data. I seem to recall hearing that MADIS then uses the solar data to calculate ET, when available.

[dalecoy]

Yes, WeatherLink is sending my solar data to CWOP, and it appears nicely (after the "L") in the raw APRS data.

[davey6693]

I've just mounted mine and I'm still intrigued by watching the THSW bounce around as cloud cover intervenes on a sunny day. If I'm outside I feel instant relief when the sun dips behind a cloud, so even though every "heat index" type of calculation is flawed in some way, this at least is my favourite attempt to describe an apparent temperature.

One related question. I've had to site mine up with my anemometer on the roof and run 100 feet of cable to the ISS (annoying, but we've been there before with discussion about the wireless anemometer transmitter only sending one data type - I'm mostly over it  ). Because of the long cable run, the solar radiation bottoms out at 7 W/m^2 overnight. It sits correctly at 0 W/m^2 with no cable extension. Having spent a day running the cable and making frequent checks, I'm pretty confident in the connections, so I'd be happy to simply use an offset on the VP2 console to zero it.  Does anyone know if it's possible? It doesn't seem to be from reading the Davis manual, but in the solar radiation sensor manual it discusses annual recalibration.

Any thoughts appreciated.

[wxtech]

I've just mounted mine and I'm still intrigued by watching the THSW bounce around as cloud cover intervenes on a sunny day. If I'm outside I feel instant relief when the sun dips behind a cloud, so even though every "heat index" type of calculation is flawed in some way, this at least is my favourite attempt to describe an apparent temperature.

One related question. I've had to site mine up with my anemometer on the roof and run 100 feet of cable to the ISS (annoying, but we've been there before with discussion about the wireless anemometer transmitter only sending one data type - I'm mostly over it  ). Because of the long cable run, the solar radiation bottoms out at 7 W/m^2 overnight. It sits correctly at 0 W/m^2 with no cable extension. Having spent a day running the cable and making frequent checks, I'm pretty confident in the connections, so I'd be happy to simply use an offset on the VP2 console to zero it.  Does anyone know if it's possible? It doesn't seem to be from reading the Davis manual, but in the solar radiation sensor manual it discusses annual recalibration.

Any thoughts appreciated.

Do you also have any lightning arrestors or filters on that line?  Is any waterproofing putty touching the conductors inside the splice or connector?  The extra length or a physical component may be adding some capacitance to the line. 
The SIM sends a power pulse to the solar sensor, then reads the return signal.  The solar sensor is only briefly powered on.  These pulses are easily affected by line capacitance.  Maybe try replacing your spliced cable with a single run CAT-5E.
I have a big reel of 4 conductor telephone wire.  Someday, I'll add that to the solar and UV sensor cables and note the effect on the console.  Interesting test.
BTW:  The sun is the biggest driver of our weather.  Every wx station should measure the intensity of the sun.  I also do UV.  Plot solar with wind as a second plot on the same graph.  Wind speeds overlay nicely over solar intensity.

[davey6693]

Thanks. No additional components on the line, as you say I think we're just looking at an artefact of the length of cable. I won't be replacing the cable since it took a couple of days to prep it, feed it through conduit and bury one third of its length (safely inside the conduit) under my lawn, so I was looking for some way to offset the numbers on the console.

[wxtech]

Hang on, I have some ideas.  I need to create your symptom here first.

[Aardvark]

take a look at my charts
http://www.weatheraardvark.com/RainGraphs/Solar-uv.htm






is this what you are seeing?  spikes?   If so those spikes are what you are seeing, it is clouds.. providing you have the sensor level

[Jim18655]

At 1.67mV/W/m² per the Davis spec, you only need .ooo2volts to get that reading. I doubt that line capacitance would cause a high reading. It should smooth out the spikes. Even at night the return value should be zero since there wouldn't be any output from the sensor. Night time readings are updated at 5 minute intervals so even a capacitive charge should dissipate between readings. I would suspect an induced voltage is being sent back because of the length of the cable. Try swapping the wires around in the cable so that you have a ground wire between the power out (yellow) and the output wire (green). I know the wires in the cable  won't easily allow that arrangement but on the ISS end the jacket could be stripped longer and the wires rearranged. I don't know how you spliced the cables together but you could do the same and use shrink wrap to seal the jacket.

[Aardvark]

can I chime in.

when you mounted the sensor, did you separate the sensor from the black case it fits in.. check that to be sure it sits firmly and it should, that it isn't outside the mounting o ring.  Sometimes moisture gets in when the sensor cools in the night, causing a short, you get the spike and during the day it heats up and the water evaporates, at night the cycle starts again.

I had that happen with a pinhole in the  case,  I was getting 3.6 at midnight with UV.. took a lot of detective work and help with that.

the other..are your wires soldered and individually wrapped?   I used self fusing tape    http://www.uline.com/BL_6422/Silicone-Self-Fusing-Tape

I wrap  spliced wires that way, solder, then wrap each wire in this tape, then the whole bundle.

If you used the RJ plugs into that nifty connector Davis sends with their product extention cord,  I'd push the cables deep into the connector and tape around it with electrical tape and then later with the self fusing tape. to get good contact or even put in some dielectric grease in the plug.

[davey6693]

Thankyou folks. I'll see if I can muster the energy to to get back on the roof and investigate these helpful suggestions, probably at the weekend.

[wxtech]

I took the UV & solar sensors from the mast and they are now on my workbench.  I have them connected to a wired VP2 system on my bench. 
All works fine with the short cables connected from the sensors to the SIM board in the ISS.  The UV indicates 0.0 and the solar is 0 on the console.
I extended the sensor cables with about 100 feet of black 4 conductor cable.  I can't duplicate the error with this much extended wire.
I'm using a fluorescent lamp to expose the sensor to a light source.  The console indicates 5 W/m^2 when light and returns to 0 when dark.
I've connected a DSO to the solar output wires.  I can see a transition on the yellow signal lead but can't capture the + voltage or signal return.  I'll get back to this project later.

[dalecoy]

Thankyou folks. I'll see if I can muster the energy to to get back on the roof and investigate these helpful suggestions, probably at the weekend.

When you do that, I suggest as a test that you get another length of good quality cable.  Prepare that cable so that it will be (somewhat) easy to do the following:

Cover the sensor and record the solar reading with the current long cable.  

Now, disconnect the current long cable (the solar reading should be zero at that time), and then swap in the test cable, and compare the solar reading.

I know that's going to be a pain to do, but it will certainly help diagnose the situation.

Note that it might take some time (up to 5 minutes) for the console to update its solar reading.

[jerryg]

Well i ordered a solar sensor and now have it installed on my tower above my web cam and annys at about 40 feet to get a clear view horizon to horizon. It is working great and i have about 60 feet of cad 5 cable on it with no problems seen. It is interesting to see the variations in level with the clouds moving by.

[irenabyss]

Hi,

I know this topic is old but I am having the same problem and wanted to see if davey6693 found a solution. I have just installed my anemometer on a mast with about 30m of Cat 5e cable as an extension. While there I ran a second Cat 5e cable with the intention of placing my solar sensor on the mast too. The solar sensor reads 7W/m^2 when on the extension cable and 0W/m^2 when directly plugged into the ISS. The cat5 is terminated with a male and female rj12 to directly accept the solar rj12

My ISS isn't in a particularly bad spot so I might just run with it off the ISS however given the effort of running the cables if anyone has a solution I'd be interested to hear it.

Thanks

[ValentineWeather]

Same here I extended cable around 150' for better sun exposure now reading 5 W/m2 at night.

I guess this is line capacitance built up per wxtech. He suggested trying cat5e cable but before doing that I was wondering if others have found a solution since it's been many years ago the thread was started.
 
I do have 2 splices unavoidable, twisted wires together and used self fusing tape followed up scotch 33 electrical. Someone mentioned solder the splices but have doubt this is solution but not 100% on this.

Any new ideas over the years?

[ValentineWeather]

Replaced the wire today this removed the 2 additional splices. Also shortened run involves burying much more cable around 80' with direct route vs 20' before but now reads zero when sensors covered.