Topic: Temperature spike today for Vantage Pro 2 aspirated weather station

[ValentineWeather]

I really wish Davis would come back with a round fitting AC fan with 5x more air flow.

Believe it or not, I'm still experimenting with slowing the flow down due to the 31's response time. May move on to a rheostat.

If I remember the fan you use has several times more flow than the electric I use. I really don't have an issue with fast response times. It is what it is, the way I look at it.

[johnd]

I've no idea when this effect might become significant, but presumably the action of the fan blades inevitably heats the air stream. So a weaker (but adequate) airflow might actually give more accurate temperature readings than a high flow system.

[ValentineWeather]

Interesting the more expensive shield Qualimetrics 8150A maker of the airport stations http://www.allweatherinc.com/ only flows 360 ft/min while the RM young 43408 has between 590-1380 depending on sensor used.
For comparison at peak solar the Davis solar is 190. So maybe the sweet spot would be double or around 360 ft/min for minimal radiation error. 

[CW2274]

I really wish Davis would come back with a round fitting AC fan with 5x more air flow.

Believe it or not, I'm still experimenting with slowing the flow down due to the 31's response time. May move on to a rheostat.

If I remember the fan you use has several times more flow than the electric I use. I really don't have an issue with fast response times. It is what it is, the way I look at it.

It pulls at 67cfm, which if my conversion is right for the diameter of the chamber it is about 340 ft/minute.

[CW2274]

I've no idea when this effect might become significant, but presumably the action of the fan blades inevitably heats the air stream. So a weaker (but adequate) airflow might actually give more accurate temperature readings than a high flow system.

Exactly what I'm trying to find out. I tend to think that possibly the air being rushed through may heat it somewhat; grasping at straws.

[ValentineWeather]

If the conversion is correct it should be well within OK range.

[CW2274]

If the conversion is correct it should be well within OK range.

Looks it.
BTW I have the 15 and the 31 in the sensor chamber, the 15 runs a consistent .8F cooler (with the offset) than the 31.

[ValentineWeather]

If the conversion is correct it should be well within OK range.

Looks it.
BTW I have the 15 and the 31 in the sensor chamber, the 15 runs a consistent .8F cooler (with the offset) than the 31.

You don't want to offset the 15. It would be running .9-lower if you did. Only the 31 needs the offset.

[CW2274]

If the conversion is correct it should be well within OK range.

Looks it.
BTW I have the 15 and the 31 in the sensor chamber, the 15 runs a consistent .8F cooler (with the offset) than the 31.

You don't want to offset the 15. It would be running .9-lower if you did. Only the 31 needs the offset.

I'm not. That's the difference with the .9 on the 31 and ZERO correction on the 15. The 15 is .8 cooler.

[ValentineWeather]

If the conversion is correct it should be well within OK range.

Looks it.
BTW I have the 15 and the 31 in the sensor chamber, the 15 runs a consistent .8F cooler (with the offset) than the 31.

You don't want to offset the 15. It would be running .9-lower if you did. Only the 31 needs the offset.

I'm not. That's the difference with the .9 on the 31 and ZERO correction on the 15. The 15 is .8 cooler.

Somethings wrong. You need to figure out which one is off. I'm leaning toward the 31 is correct just because I have 4 matching very nicely even when compared with the 15. 
Could you explain the setup, are transmitters separate or are you unplugging one sensor and plugging the other in. If using same transmitter older pre 2016 code you remove offset on 15 and go -.9 on 31 making sure you have the correct sensor plug each time.

Just eliminating any possible snafu I'm famous for until I reexamine what I'm doing.

[CW2274]

They're both in one chamber and I merely switch plugs. Without ANY correction the 15 reads 1.7F cooler than the 31, so with the -.9 dialed in for the 31 the 15 still reads 0.8 cooler.

[ValentineWeather]

They're both in one chamber and I merely switch plugs. Without ANY correction the 15 reads 1.7F cooler than the 31, so with the -.9 dialed in for the 31 the 15 still reads 0.8 cooler.

That confirms it. I lean toward the 15 being bad with the 31 new.  Do you have another sensor like the older 11 you could plug in and compare provided its still accurate?

Ryan will take care of you if its the 31 I'm sure.

[CW2274]

Look at the obs before 3:03pm, then after. The after has the thick cloth on the bottom. Very telling, MUCH more of what I'm after.http://www.wrh.noaa.gov/mesowest/getobext.php?wfo=twc&sid=C2274&num=48

[CW2274]

They're both in one chamber and I merely switch plugs. Without ANY correction the 15 reads 1.7F cooler than the 31, so with the -.9 dialed in for the 31 the 15 still reads 0.8 cooler.

That confirms it. I lean toward the 15 being bad being the 31 is new.  Do you have another sensor like the older 11 you could plug in and compare provided its still accurate?

Ryan will take care of you if its the 31 I'm sure.

I'm not so sure. If I were a betting man I'm guessing the 15 runs a little cool and the 31 a little warm.

[ValentineWeather]

They're both in one chamber and I merely switch plugs. Without ANY correction the 15 reads 1.7F cooler than the 31, so with the -.9 dialed in for the 31 the 15 still reads 0.8 cooler.

That confirms it. I lean toward the 15 being bad being the 31 is new.  Do you have another sensor like the older 11 you could plug in and compare provided its still accurate?

Ryan will take care of you if its the 31 I'm sure.

I'm not so sure. If I were a betting man I'm guessing the 15 runs a little cool and the 31 a little warm.

I think the 31 is dead on. .8 is too much.
Change fans out I looked for the Cooltron on Amazon and can't find it. They do have this version looks ok for Tucson area. http://www.amazon.com/AC-Infinity-AXIAL-Muffin-Cooling/dp/B009OXSFBA/ref=sr_1_1?ie=UTF8&qid=1462748586&sr=8-1&keywords=80mm+ac+fan

[CW2274]

They're both in one chamber and I merely switch plugs. Without ANY correction the 15 reads 1.7F cooler than the 31, so with the -.9 dialed in for the 31 the 15 still reads 0.8 cooler.

That confirms it. I lean toward the 15 being bad being the 31 is new.  Do you have another sensor like the older 11 you could plug in and compare provided its still accurate?

Ryan will take care of you if its the 31 I'm sure.

I'm not so sure. If I were a betting man I'm guessing the 15 runs a little cool and the 31 a little warm.

I think the 31 is dead on. .8 is too much.
Change fans out I looked for the Cooltron on Amazon and can't find it. They do have this version looks ok for Tucson area. http://www.amazon.com/AC-Infinity-AXIAL-Muffin-Cooling/dp/B009OXSFBA/ref=sr_1_1?ie=UTF8&qid=1462748586&sr=8-1&keywords=80mm+ac+fan

You certainly may be right. The fan I have is fine, just need to better control the flow as my cloth post above seems to bring the results I'm after. Accuracy, as silly as it seems, is not my main concern here at the moment, but CONSISTENCY of the temp from one minute to the next is. I want to be able to look at my console and know that it's actually the temp it is without having to preview the last 15 minutes to average it out.

[CW2274]

The more I see this cloth mod, the more I like it. Tried others, but this so far is the best at helping neutralize the roller coaster 31. However, I need to incorporate it so it always stays dry.

[dendrite]

Look at the obs before 3:03pm, then after. The after has the thick cloth on the bottom. Very telling, MUCH more of what I'm after.http://www.wrh.noaa.gov/mesowest/getobext.php?wfo=twc&sid=C2274&num=48

Heh...good case of "different folks, different strokes". I would personally prefer your more responsive setup. I can understand you wanting to keep your climo measuring methods consistent though.

[CW2274]

Look at the obs before 3:03pm, then after. The after has the thick cloth on the bottom. Very telling, MUCH more of what I'm after.http://www.wrh.noaa.gov/mesowest/getobext.php?wfo=twc&sid=C2274&num=48

Heh...good case of "different folks, different strokes". I would personally prefer your more responsive setup. I can understand you wanting to keep your climo measuring methods consistent though.

Thanks for seeing my point, but all due respect, couldn't disagree more. Do you think that "official" measurements that truly represent the temp act like the 31? Not without averaging, and that way to me is far preferable.  To see the temp 80 one moment, 84 the next, then 80 again, to me is complete bulls**t even though it's completely accurate for that "split second".

[ValentineWeather]

4° changes over short period is drastic. I'm not seeing changes like that at all. Going with the 21 cfm fan may help or its possible you do have a bad sht31. I was more concerned about the .8 difference before I read this.

I emailed AC Infinity asking why they no longer sell the Cooltron FA8025B11T7-51 which I purchased (2 each) in 2013. They still carry the fan but not on Amazon anymore and because I don't like using my debit card and they don't have paypal I would rather order through Amazon.

The Cooltron is rated below zero and IMO a great fan. I've never broke one yet and they run 24/7 for years. 

[dendrite]

Look at the obs before 3:03pm, then after. The after has the thick cloth on the bottom. Very telling, MUCH more of what I'm after.http://www.wrh.noaa.gov/mesowest/getobext.php?wfo=twc&sid=C2274&num=48

Heh...good case of "different folks, different strokes". I would personally prefer your more responsive setup. I can understand you wanting to keep your climo measuring methods consistent though.

Thanks for seeing my point, but all due respect, couldn't disagree more. Do you think that "official" measurements that truly represent the temp act like the 31? Not without averaging, and that way to me is far preferable.  To see the temp 80 one moment, 84 the next, then 80 again, to me is complete bulls**t even though it's completely accurate for that "split second".

Well we grew accustomed to the response time of mercury thermometers and accepted them as official. If, we had started with digital sensors like the SHT31, the way we measure, manipulate, and report temperature may be different. The ASOS sensors can jump around 3-5F/min at times before the averaging that you mention. Obviously NOAA thought the "jumpiness" of the digital instrumentation didn't represent a mercury thermometer very well and probably thought it would greatly affect climo trends with warmer highs and cooler lows being reported.

In the end it's all about what you want and what you're happy with. I had insane jumps with the SHT75...with the SHT31, not quite as much. Others have had different experiences with the sensors. I'm on a hillside and my highs tend to run a little cooler than local sites and my lows run a little warmer on radiational cooling nights with my 31. I'm happy with my 31 and 45CFM fan. I wasn't implying that the faster response was better or that your way was wrong...just that different people sometimes want to see different things with their data.

[dalecoy]

Look at the obs before 3:03pm, then after. The after has the thick cloth on the bottom. Very telling, MUCH more of what I'm after.http://www.wrh.noaa.gov/mesowest/getobext.php?wfo=twc&sid=C2274&num=48

What is the effect on humidity measurements?

[CW2274]

Look at the obs before 3:03pm, then after. The after has the thick cloth on the bottom. Very telling, MUCH more of what I'm after.http://www.wrh.noaa.gov/mesowest/getobext.php?wfo=twc&sid=C2274&num=48

What is the effect on humidity measurements?

None that I can tell. Merely seems to smooth the temp curve. Still not sold though, more to do. Good thing I'm retired.

[kcidwx]

You mean there's no options with all the fancy PWS software out there to do temperature averaging?  Personally, I wouldn't mess with the sensor. It should be done software side.

Also you'll see bigger minute by minute temperature fluctuations in large urban areas versus rural areas due to heat coming off structures and roads with ever changing wind speed and even slight variance in wind direction.

[CW2274]

You mean there's no options with all the fancy PWS software out there to do temperature averaging?  Personally, I wouldn't mess with the sensor. It should be done software side.

I wish. WL can average, but only in the "browse records" area. So what. I want it displayed on my console and sent out that way too.

Ever since I installed the 31, I've gone from always the "cool kid on the block" to now damn near always the warm one, ALOT warmer. Never was with the 15. Something's amiss.