Unusual Modifications or Applications For Davis Sensors?

[Heirphoto]

North of 60, Are you connecting the 7817 directly to the VP2 ISS in place of the regular temp unit?  Maybe that is where the difference is.

The expensive 2 wire version goes in the Soil Temp/Leaf Wetness unit and I was wondering if the 7817 with just two of the correct wires being used would work in that unit, not the ISS.

[Bushman]

Must be. 

[north of 60]

yes i plug 7817 wizard/monitor temp sensor in to the iss temp/hum slot,  it doesn't work.  i had to get this one which cost double  http://www.davisnet.com/weather/products/weather_product.asp?pnum=06475

[Bushman]

Yet this one is specifically stated to work with anemometer stn.  http://www.davisnet.com/weather/products/weather_product.asp?pnum=06477

[north of 60]

same sensor as 7817 but which colour wires used must be different.  i notice the wire layout of both the 7817 and stainless steel one is same in the rj connector end but the sensor must use not use same wires.   maybe if on cuts wire and see which ones work.

[wxtech]

On the 7817 temp probe davis says red and black are common, yellow and green are the variable leads. So I assume one needs one of the black or red paired with one of the yellow or green to get a reading. I think this sensor comes with an RJ connector whre the metal probe is just two wires.
Tony

Resistance sensors [RTDs] has 2 and sometimes 4 wires.  On a 4 wire measurement system, the wires are labeled; source low, sense low which are connected to one side of the detector.  Source high, and sense high are connected to the other side of the detector.  Having the excitation [source] current flowing in one pair allows the other pair to be used for the sense voltage to be measured by the metering circuitry.
If the device is expecting 2 wires, the 4 wire resistance detector will work OK as long as you use one of the high leads and one of the low leads.  Or you can connect the pairs in parallel; source low to sense low.  Connect source high to sense high and that converts the 4 wire detector to a 2 wire detector. 
A 4 wire system is more accurate than a 2 wire system due to the voltage drop in the source leads.

[Heirphoto]

I finished up my "fog detector" last night using a Davis leaf wetness sensor as described in a much earlier thread. I mounted it upside down under an 8" PVC pipe cap (6" would have been more than large enough) to shield it from moisture falling from above (dew). In theory it should only detect suspended moisture such as fog of mist. Of course it has been 90+ here for well over a week and no rain for 11 days straight so I doubt I will have readings any time soon. I have another wetness sensor mounted in the open next to it to indicate dew, rain or frost. Not extremely useful readings but I love to tinker and am geeky enough to simply enjoy gathering data  

I started a wet bulb/dry bulb setup based on what an earlier poster to this thread suggested. Mine is being housed in a 3" PVC Tee with a solar powered fan on the top to draw a constrant stream of air past the bulbs (two Davis 6470 sensors). A drain grate on the bottom keeps the wildlife out. I found a mini-solar fan on ebay designed to fit over PVC exhaust vents on houses or RVs. It is rain tight from the top, and exhuasts under the weatherproof cap.

Another cool little thing I built was small plastic enclosures to hold the unused spools of Davis wire. On short runs there is that pesky coil to deal with and I didn't like it just hanging out in the weather. I used a 3" PVC pipe cap with a hole drilled in the side and bolted to an electrical EMT conduit clamp which tightehs around the station mounting pole. The coil of excess wire tucks inside held by a plastic wire tie trough a drilled hole. Makes a neat installation and just looks like some type of small instrument mounted to the pole.

Here is a link to my Flickr page where you can see my station and newest modifications. There is also a Stephenson screen project pictured.

http://www.flickr.com/photos/28161661@N03/

Thanks,
Tony

[wxtech]

Tony,
You need a transmissometer.  http://www.lexingtonwx.com/techdata/images/TO31M1-2GMQ-10-61.pdf see the eqpt pics on page 6.
It measures the transmissivity of light detecting anything that interrupts vision such as fog, smoke, rain/snow.
Al

[Bushman]

I'll bet those are cheap. 

[d_l]

Another cool little thing I built was small plastic enclosures to hold the unused spools of Davis wire. On short runs there is that pesky coil to deal with and I didn't like it just hanging out in the weather. I used a 3" PVC pipe cap with a hole drilled in the side and bolted to an electrical EMT conduit clamp which tightehs around the station mounting pole. The coil of excess wire tucks inside held by a plastic wire tie trough a drilled hole. Makes a neat installation and just looks like some type of small instrument mounted to the pole.

Tony, that sounds like a neat idea.  If you ever get picture upload working, I'd sure like to see what you did.  I've started thinking about something like that for my VP2 set up.

[Heirphoto]

Okay, I can get a link to go to flickr for those who want to see what I have been working on. It is in a previous post and here it is again:

http://www.flickr.com/photos/28161661@N03/

I will probably move the Soil Temp station and related sensors to their own mast next to the ISS/Ano mast as this seems to load the current mast a bit too much being piggybacked on the side as it is.


I'll upload photos of the wetbulb setup next weekeknd when it is finished. Still awaiting the fan.

Tony

[moehoward4]

I tried a little experiment this PM...I put the 7817 temp probe into the temp port on an anemometer trans kit and got a temp reading 41% HIGHER so I would have to agree with north of 60, that the 'old' temp sensors will not work with the 'new' VP2 setups. After checking Davis specs, the 10k ohms must be the issue. The 7817 specs were the only one that mention ANYTHING about 'ohms'. It also shows that Davis is wrong saying that the 7817 can be used in the Anny trans kit. It shoots my idea of using the 7817 as a temp probe in a Leaf/Soil station.    Jack

[SLOweather]

Under the "Unusual Applications" part of this thread....

I have a spare soil moisture/leaf wetness station, and temp and soil moisture probes. Been thinking about burying them in the middle of my compost pile. Every time I turn it, I take the temp manually, and it's been running 115 F to 123 F, with ambient in the 70s.

[Heirphoto]

Finally had the right weather conditions to test my "fog" sensor yesterday. We had really heavy rains here over the weekend with a fog most of yesterday morning during and after the rain. I scrolled through my sensor readings on the VP2 console and leaf Wetness 1 was reading 15 indicating the rain deposited on it and the well sheltered one, Leaf Wetness 2 was reading a 9. The large plastic dome (8" PVC pipe cap) kept the rain water away but did allow the fog to register on the inverted and covered leaf wetness unit.

Still need a little free time to finish my wet/dry bulb unit. I am using a 3" PVC tee with a small solar vent pipe cap fan and a pair of Davis temp probes inserted from the side of the tee through a PVC cap. The bottom of the tee has a PVC drain cover for a bug shield. One sensor will be kept damp with a cotton wick and a bicycle water bottle and holder mounted to the tee.

Tony

[SLOweather]

Today, after reading the manuals to figure out how it do it, I realigned my two soil moisture/leaf wetness stations so the first one is soil only, and the second one is leaf wetness only. Both can read some temps.

The #1 temp probe on the leaf station I buried in the compost pile to monitor the temperature of the biological activity.

Right now (8:30 PM PST), with an air temperature of 48 F, and a soil temperature in the raised be garden of 50 F, the middle of the compost pile is 111 F and rising (it cooled off when I disturbed it to implant the temp probe.