Topic: Does the Davis Vantage Pro 2 24hr FARS performs well?

[WxLover16]

The best response time I've gotten from any Sensirion sensor is with the SHT75. Of course that sensor module has the least thermal mass of any of them so it's response shouldn't be much of a surprise. I dealt with frequent RH issues with them after a few weeks of use so I gave up on them. I swear I was getting faster than 12s updates, but don't hold that to me. I'd assume the update interval is handled by the ISS board and not the temp/hum module board, correct? That's the only sensor I used that had a non-Davis PCB.

I'd love to see a similar sensor for the SHT31/35 as the SHT75 was for the SHT15. Of course you have the different sensor versions (Davis uses the legacy IIRC) so maybe it wouldn't be plug-n-play like the 75 is.

There are times when there is rapid warming or cooling I could swear that it is updating at faster than the 10-12 second interval that it says. Maybe more like 5-10.

[fish-on]

So here is my take on the original question. I have been using a dfars for a year now and when I upgraded to that from a passive setup, my accuracy increased significantly. I have my ISS station mounted over my lawn in an area the gets fairly good sun all day. The key here is where you locate the ISS. Even with the original passive setup, when the temps got up to the 90 degree range , my readings where only bumping up around 3-4 degrees. With the dfars in the same location, only 1-2 degrees. When it snowed both setups looked the same at nights and the dfars improved the low temp reading during the days when there was sufficient sun to supply the panel with energy. I just upgraded my dfars to the 24hour fars setup. I have 2 days of very hot weather and we now are going to cool off for awhile. What I have noticed now is the temp and humidity readings are even more stabile and now my temp reading has no more than .75 degree increase when compared to my precision mercury gauge setting next to ISS located out of direct sunlight. When I say .75 degrees, that might be a little high. I suspect over time I should easily be able to see a +/- .5 error. So getting back to original question about the 24hour fars setup worth the price upgrade, in my opinion it is living up to what I expected. More stable and accurate readings. Got all the parts from SI and that was a good experience. Ryan offered his opinion on a 24 hour fars upgrade path and that was information that helped to make my path forward for my upgrade. I decided to spend the money and upgrade to the Davis design. Thanks Ryan for your help and quick service.

[ValentineWeather]

Where station is located does make a difference. Fars or No Fars especially with Summer temperatures . I saw proof this summer where a section of  unwatered grass died during our drought and was consistently recording +1-2° highs over same duplicate Fars setup some 40 yards away with sensor located over watered grass.  Grass cools more than I ever thought especially with low wind conditions.

If I can see this difference in my own backyard just think about all the stations located nationally over gravel (some very dark), hot sand 130°, near tarmac 140° just how inconsistent temperatures are now vs the Stevenson screen era where the recommendation was place Stevenson screen over short cut grass.

[jgentry]

I just installed a 24hr FARS over at a friend's business just recently  and it's set up above some concrete. So far, I haven't noticed any temperature readings of being too warm. Also, I've seen recommendations that the humidity sensor should be located over natural dirt or gravel. I do know that at nighttime, the temperature will be colder over a grassy surface compared to plain dirt.

[ValentineWeather]

I just installed a 24hr FARS over at a friend's business just recently  and it's set up above some concrete. So far, I haven't noticed any temperature readings of being too warm. Also, I've seen recommendations that the humidity sensor should be located over natural dirt or gravel. I do know that at nighttime, the temperature will be colder over a grassy surface compared to plain dirt.

Well then I guess I'm wrong if your friends station is okay,  I'll try some concrete too. 

[jgentry]

Keep in mind that the 24hr FARS has only been installed for 2 full days and we haven't had any really hot weather (except for the mugginess) in the last few days. I would think the FARS would eliminate any errorness readings that the concrete could induce? But I will say that so far, the DPs has matched up really well with the nearby ASOS (located around 15 miles N), since I installed the FARS there.

The SHT-31 sensor in that shield did top off at 99% one morning but I was sure hoping it would report 100% since there was foggy at misty. But oh well...

[jgentry]

Here is the set up on the FARS

[CW2274]

Also, I've seen recommendations that the humidity sensor should be located over natural dirt or gravel.

That's a new one. Your ISS should normally be sited in a place that's indicative of your surroundings. For instances, I am surrounded by sand, rock, and desert vegetation so I wouldn't site my ISS over grass, even if I had it.

[CW2274]

I would think the FARS would eliminate any errorness readings that the concrete could induce?

Not at all. In fact, the only thing FARS will do for a poorly sited ISS is show the error faster and more accurately.
The picture with the concrete is fine, too small to matter and especially being white.

[ValentineWeather]

Here is the set up on the FARS

That's fine not enough concrete to make much difference. When the heat really turned up is when I was seeing the biggest differences grass vs dead grass and sand. I'm talking 100+ with 110.8° one day vs 108.1° over the grass.

[CW2274]

Here is the set up on the FARS

When the heat really turned up is when I was seeing the biggest differences grass vs dead grass and sand. I'm talking 100+ with 110.8° one day vs 108.1° over the grass.

Jeez, just another example of how important siting can be.

[ValentineWeather]

I was consistently warmer during July over the grassless dead ground until temperatures got back down into 70's-80's and rains returned at same time. Now everything has evened out again with highs almost the same but the vegetation has filled in so much I'm mowing again.   

[CW2274]

I'm mowing again. 

God, I SO don't miss that and haven't done it since 1979 when I had to mow one side of our runway where the tractor couldn't reach due to the runway lights. No wonder I'm traumatized...

[ValentineWeather]

I'm mowing again. 

God, I SO don't miss that and haven't done it since 1979 when I had to mow one side of our runway where the tractor couldn't reach due to the runway lights. No wonder I'm traumatized...

  I've got a rider for first time. Its nice and fast.

[CW2274]

I'm mowing again. 

God, I SO don't miss that and haven't done it since 1979 when I had to mow one side of our runway where the tractor couldn't reach due to the runway lights. No wonder I'm traumatized...

  I've got a rider for first time. Its nice and fast.

Oh no, not me, push baby, and it was 100F with 100% humidity to boot (couldn't resist, but it was HOT). What's even funnier/ludicrous is that operations were still ongoing and I had a radio so the tower could "warn" me when there was an arrival or departure, but I couldn't hear it over the mower. At least they got a hold of me before the C5 landed. Now THAT was cool.
Sorry for the OT.