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

[CW2274]

CW2274, please check your PMs.

I did.

[WxLover16]

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.

Just out of curiosity, why do you have such a powerful fan up in NH? I'm sure it works great (and is a personal preferance most likely), but so far north you wouldn't think it would be needed. Though maybe I'm totally off and you do, especially in summer. Was just wondering. Also I wonder how much stronger your fan is than my stock Davis fan and how much of a difference it makes.

[WxLover16]

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.

I loved the awesome response time with the 31 filter off. I don't like the averaging out or whatever. I like to know exactly what the temp is at any given second and with the 31's filter off it was amazing watching all the fluctuations. But, not wanting to dirty up or contaminate the sensor with dirt or debris, cautious me went ahead and put the filter back on. Definitely slower response time but it's all good.

[WxLover16]

Just to experiment how strong my fan is during a noon sun, I took my debit card to the intake and it did not stay but a paper towel did. I suppose that's good enough.

[CW2274]

Just to experiment how strong my fan is during a noon sun, I took my debit card to the intake and it did not stay but a paper towel did. I suppose that's good enough.

A debit card won't create a full seal around the bottom and probably too heavy for the stock fan even if it did.
IIRC, the fan I run at 67cfm is ~ 3.5 times stronger than stock at full sun and will easily hold a thick business envelope with the contents still inside. Do I need all this power, probably not, but more importantly, I know it's always there.

[WxLover16]

Just to experiment how strong my fan is during a noon sun, I took my debit card to the intake and it did not stay but a paper towel did. I suppose that's good enough.

A debit card won't create a full seal around the bottom and probably too heavy for the stock fan even if it did.
IIRC, the fan I run at 67cfm is ~ 3.5 times stronger than stock at full sun and will easily hold a thick business envelope with the contents still inside. Do I need all this power, probably not, but more importantly, I know it's always there.

Do you keep it at the same speed 24/7 or turn it down at night when that amount of aspiration isn't as necessary anymore? That is insane though, thick full business envelope easily. That is heavy duty aspiration. This past summer was about our 2nd hottest on record I believe, my VP2 recorded 71 days AOA 90 degrees which is insane for here. Wondering if I should go for something other than stock. I'm assuming a little more aspiration (but not too much) could only do more good than harm on my afternoon readings.

[CW2274]

Just to experiment how strong my fan is during a noon sun, I took my debit card to the intake and it did not stay but a paper towel did. I suppose that's good enough.

A debit card won't create a full seal around the bottom and probably too heavy for the stock fan even if it did.
IIRC, the fan I run at 67cfm is ~ 3.5 times stronger than stock at full sun and will easily hold a thick business envelope with the contents still inside. Do I need all this power, probably not, but more importantly, I know it's always there.

Do you keep it at the same speed 24/7 or turn it down at night when that amount of aspiration isn't as necessary anymore? That is insane though, thick full business envelope easily. That is heavy duty aspiration. This past summer was about our 2nd hottest on record I believe, my VP2 recorded 71 days AOA 90 degrees which is insane for here. Wondering if I should go for something other than stock. I'm assuming a little more aspiration (but not too much) could only do more good than harm on my afternoon readings.

100%, 24/7. Yes, it's strong, makes an impressive "whooshing" sound from the suction.
I switched because I was tired of replacing stock fans, and we've spoken of my difficult ISS placement for service. The added benefit is indeed the greater aspiration, which I (and a few others) felt the stock motor was somewhat lacking. With this, never a worry.  

[WxLover16]

Just to experiment how strong my fan is during a noon sun, I took my debit card to the intake and it did not stay but a paper towel did. I suppose that's good enough.

A debit card won't create a full seal around the bottom and probably too heavy for the stock fan even if it did.
IIRC, the fan I run at 67cfm is ~ 3.5 times stronger than stock at full sun and will easily hold a thick business envelope with the contents still inside. Do I need all this power, probably not, but more importantly, I know it's always there.

Do you keep it at the same speed 24/7 or turn it down at night when that amount of aspiration isn't as necessary anymore? That is insane though, thick full business envelope easily. That is heavy duty aspiration. This past summer was about our 2nd hottest on record I believe, my VP2 recorded 71 days AOA 90 degrees which is insane for here. Wondering if I should go for something other than stock. I'm assuming a little more aspiration (but not too much) could only do more good than harm on my afternoon readings.

100%, 24/7. Yes, it's strong, makes an impressive "whooshing" sound from the suction.
I switched because I was tired of replacing stock fans, and we've spoken of my difficult ISS placement for service. The added benefit is indeed the greater aspiration, which I (and a few others) felt the stock motor was somewhat lacking. With this, never a worry.

Did you order your fan online or is it store bought? I might look into getting this, though not totally sure I need it in my climate.

[CW2274]

Online for about $15.
If your fan is easy to check daily, I wouldn't sweat it. That being said, even if mine was easy to check, I would still absolutely run the big boy.

[dalecoy]

I don't like the averaging out or whatever. I like to know exactly what the temp is at any given second

Of course, you know that a station 12 inches away in any direction would have entirely different second-by-second graphs.

...but I digress.....

[WheatonRon]

Just to experiment how strong my fan is during a noon sun, I took my debit card to the intake and it did not stay but a paper towel did. I suppose that's good enough.

Maybe instead of a debit card, you used a credit card, the results would have been more favorable?

[WxLover16]

Online for about $15.
If your fan is easy to check daily, I wouldn't sweat it. That being said, even if mine was easy to check, I would still absolutely run the big boy.

Doesn't your powerful fan cause your temperature to run warmer at night on calm clear still nights though?

[CW2274]

Online for about $15.
If your fan is easy to check daily, I wouldn't sweat it. That being said, even if mine was easy to check, I would still absolutely run the big boy.

Doesn't your powerful fan cause your temperature to run warmer at night on calm clear still nights though?

Honestly, I'm not sure. Whereas I'm inline with the airport always in the day, at night my low is usually about 3F cooler than the airport.

[WxLover16]

I don't like the averaging out or whatever. I like to know exactly what the temp is at any given second

Of course, you know that a station 12 inches away in any direction would have entirely different second-by-second graphs.

...but I digress.....

Quite possibly true, but I have one station so I would only care what my station would read at any given time.

[WxLover16]

Online for about $15.
If your fan is easy to check daily, I wouldn't sweat it. That being said, even if mine was easy to check, I would still absolutely run the big boy.

Doesn't your powerful fan cause your temperature to run warmer at night on calm clear still nights though?

Honestly, I'm not sure. Whereas I'm inline with the airport always in the day, at night my low is usually about 3F cooler than the airport.

That could also be attributed to the landscape around you. I know nothing about your area, but I do know that airports tend to run warmer at night due to air traffic so the air can't settle. You might just live in a cooler area.

[Old Tele man]

Not many homes have as many square-acres of "thermal-sink" asphalt & concrete runway(s) near them as an airport does.

[CW2274]

Online for about $15.
If your fan is easy to check daily, I wouldn't sweat it. That being said, even if mine was easy to check, I would still absolutely run the big boy.

Doesn't your powerful fan cause your temperature to run warmer at night on calm clear still nights though?

Honestly, I'm not sure. Whereas I'm inline with the airport always in the day, at night my low is usually about 3F cooler than the airport.

That could also be attributed to the landscape around you. I know nothing about your area, but I do know that airports tend to run warmer at night due to air traffic so the air can't settle. You might just live in a cooler area.

Ha! The only thing flying around this airport at night are bats.

[CW2274]

Not many homes have as many square-acres of "thermal-sink" asphalt & concrete runway(s) near them as an airport does.

Good point.

[dendrite]

Doesn't your powerful fan cause your temperature to run warmer at night on calm clear still nights though?

Why would that be true?

[BigOkie]

Doesn't your powerful fan cause your temperature to run warmer at night on calm clear still nights though?

Why would that be true?

Thermal dynamics?

[dendrite]

Doesn't your powerful fan cause your temperature to run warmer at night on calm clear still nights though?

Why would that be true?

Thermal dynamics?

Do you have a thermodynamic explanation? Because I can't come up with one. The only possibility could possibly be the fan exhaust getting resucked into the bottom of the FARS like it did with those old ASOS hygrothermometers. I've actually noticed slightly cooler mins due to the faster response time.

I'm not adiabatically mixing the low levels with my little 12V fan. The radiational cooling outside of the sensor chamber remains unchanged...I'm just pulling the air in.

[WxLover16]

Doesn't your powerful fan cause your temperature to run warmer at night on calm clear still nights though?

Why would that be true?

Maybe I'm way off here, but I just assume that with that much air being drawn across the sensor, the air can't "settle" quite as much leading to a higher minimum temperature. Again, maybe I'm completely off.

[CW2274]

Doesn't your powerful fan cause your temperature to run warmer at night on calm clear still nights though?

Why would that be true?

The only possibility could possibly be the fan exhaust getting resucked into the bottom of the FARS like it did with those old ASOS hygrothermometers.in.

To further add, I believe I'm running about as strong of a fan as anyone here and certainly don't have this problem, so it's highly dubious that anyone else would experience this phenomena with the 24hr ISS design.

[CW2274]

Doesn't your powerful fan cause your temperature to run warmer at night on calm clear still nights though?

Why would that be true?

Maybe I'm way off here, but I just assume that with that much air being drawn across the sensor, the air can't "settle" quite as much leading to a higher minimum temperature. Again, maybe I'm completely off.

There are dynamics involved, only problem is I personally have no idea what they are.

[Old Tele man]

Compressing air will heat it up, but simply sucking it through a "normal-sized" orifice (ie: not getting into venturi-flow region) won't change temperature.