Author Topic: ASOS visit with VP2 in hand  (Read 6367 times)

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Offline ValentineWeather

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Re: ASOS visit with VP2 in hand
« Reply #50 on: July 12, 2017, 12:14:50 PM »
ASOS 1088 specs finally...
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Offline CW2274

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Re: ASOS visit with VP2 in hand
« Reply #51 on: July 12, 2017, 03:16:58 PM »
ASOS 1088 specs finally...
Insert Rodney Dangerfield "No respect I tell ya, no respect". I posted this about 4-5 months ago having a "discussion" about whether ASOS's where aspirated or not. So I supplied this along with your pic... ;)
https://upload.wikimedia.org/wikipedia/commons/c/c3/2013-09-19_09_28_07_ASOS_HO-1088_thermometer_at_Eureka_Airport%2C_Nevada.JPG

Offline ValentineWeather

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Re: ASOS visit with VP2 in hand
« Reply #52 on: July 12, 2017, 03:32:23 PM »
ASOS 1088 specs finally...
Insert Rodney Dangerfield "No respect I tell ya, no respect". I posted this about 4-5 months ago having a "discussion" about whether ASOS's where aspirated or not. So I supplied this along with your pic... ;)
https://upload.wikimedia.org/wikipedia/commons/c/c3/2013-09-19_09_28_07_ASOS_HO-1088_thermometer_at_Eureka_Airport%2C_Nevada.JPG

You lost me  :?:
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Offline CW2274

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Re: ASOS visit with VP2 in hand
« Reply #53 on: July 12, 2017, 03:38:38 PM »
ASOS 1088 specs finally...
Insert Rodney Dangerfield "No respect I tell ya, no respect". I posted this about 4-5 months ago having a "discussion" about whether ASOS's where aspirated or not. So I supplied this along with your pic... ;)
https://upload.wikimedia.org/wikipedia/commons/c/c3/2013-09-19_09_28_07_ASOS_HO-1088_thermometer_at_Eureka_Airport%2C_Nevada.JPG

You lost me  :?:
It was my poor attempt at humor. I posted this pic months ago, I guess you didn't see it. http://tslinc.com/wp-content/uploads/2010/01/hygrothermometer-data-sheet-rev.pdf

Offline ValentineWeather

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Re: ASOS visit with VP2 in hand
« Reply #54 on: July 12, 2017, 03:48:50 PM »
Yes I either missed it or didn't sink in or just another senior moment. Was looking for the updated specs after what was linked to the publication from 1998. This is more what I expected.

So someone questioned if ASOS was aspirated :?: Now that's hilarious... :lol:
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Offline CW2274

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Re: ASOS visit with VP2 in hand
« Reply #55 on: July 12, 2017, 03:54:43 PM »
Yes I either missed it or didn't sink in or just another senior moment. Was looking for the updated specs after what was linked to the publication from 1998. This is more what I expected.

So someone questioned if ASOS was aspirated :?: Now that's hilarious... :lol:
Even after posting BOTH pics, he still wanted to argue. I eventually gave up. :roll: :roll:

Offline ValentineWeather

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Re: ASOS visit with VP2 in hand
« Reply #56 on: July 12, 2017, 04:11:02 PM »
As Bill would say...
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Offline CW2274

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Re: ASOS visit with VP2 in hand
« Reply #57 on: July 12, 2017, 04:34:59 PM »
 :lol: Hadn't heard that one before... :lol:

Offline kcidwx

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Re: ASOS visit with VP2 in hand
« Reply #58 on: July 12, 2017, 04:41:50 PM »
Here's the brochure on the Vaisala DTS-1 sensor shield. Basically you can have your own DTS-1 if you purchase this shield (HMT330MIK) and the Vaisala HMT337 temperature/humidity transmitter.


http://www.vaisala.com/Vaisala%20Documents/Brochures%20and%20Datasheets/HMT330MIK-Datasheet-B210944EN-D-LoRes.pdf


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Offline CW2274

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Re: ASOS visit with VP2 in hand
« Reply #59 on: July 12, 2017, 05:43:13 PM »
I like the brochure stating what the rest of us already know...
"In weather observations dew
formation makes reliable humidity
measurement difficult."
Indeed.

Offline kcidwx

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Re: ASOS visit with VP2 in hand
« Reply #60 on: July 12, 2017, 09:42:13 PM »
Back in December I did test the SHT31 in a true 100% RH test environment and achieved these results. You can see the condensation.

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Offline CW2274

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Re: ASOS visit with VP2 in hand
« Reply #61 on: July 12, 2017, 10:03:50 PM »
Back in December I did test the SHT31 in a true 100% RH test environment and achieved these results. You can see the condensation.

Very nice. In the temp world that's 100, I assume in the humidity world that applies here too?

Offline kcidwx

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Re: ASOS visit with VP2 in hand
« Reply #62 on: July 14, 2017, 08:45:57 AM »
I should also state that I tested three SHT31's in the 100% RH environment at the same time and got mixed results. However, after looking at the specs, the maximal tolerance at 100% is 3.5%. So they would be considered in specification. The sensor in front in the photo below is the one in the photo I posted above. For that sensor I was testing repeatability. That is the sensors ability to indicate the same value when exposed to the same conditions.




The sensors maximum allowable error is 2.5% and that escalates above 90% RH.





While I was at it, I ran the daughters WMII sensor through the same test. It did get to 100% but it took 38 minutes.

« Last Edit: July 14, 2017, 10:48:52 AM by kcidwx »
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Offline ValentineWeather

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Re: ASOS visit with VP2 in hand
« Reply #63 on: July 14, 2017, 09:10:46 AM »
I've noticed a slight difference humidity also between my 3 VP2's aspirated. I run 3 stations #1&2  are over lawn, #4 is my portable located different area over less grass and more dirt. I switch over to #4 when I water the lawn every 3rd day.
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Online jgentry

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Re: ASOS visit with VP2 in hand
« Reply #64 on: July 15, 2017, 12:14:10 PM »
I found out that the specs from the RAWS station quite interesting...

http://www.ncforestservice.gov/fire_control/pdf/RNTN01.pdf
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Online Old Tele man

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Re: ASOS visit with VP2 in hand
« Reply #65 on: July 15, 2017, 01:01:41 PM »
Summary quote from page 3: "Ultimately, the station owner is responsible for ensuring the station is delivering
acceptable weather data."
SYS: Davis VP2 Vue/WL-IP & Envoy8X/WL-USB;
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CWOP: DW6988 - 2 miles NNE of Cortaro, AZ
WU - KAZTUCSO202, Countryside

Online jgentry

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Re: ASOS visit with VP2 in hand
« Reply #66 on: July 15, 2017, 01:26:44 PM »
Davis Vantage Pro2. SHT-75. WU: KXALJEMI2 & KALTHORS2. CWOP/APRS: C6353 & E6358

  

Online jgentry

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Re: ASOS visit with VP2 in hand
« Reply #67 on: July 15, 2017, 01:27:23 PM »
Summary quote from page 3: "Ultimately, the station owner is responsible for ensuring the station is delivering
acceptable weather data."


That is definitely true!
Davis Vantage Pro2. SHT-75. WU: KXALJEMI2 & KALTHORS2. CWOP/APRS: C6353 & E6358

  

Offline ValentineWeather

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Re: ASOS visit with VP2 in hand
« Reply #68 on: July 15, 2017, 02:47:18 PM »
And here is the specs of the AWOS stations
http://www.allweatherinc.com/wp-content/uploads/AWOS-III-PTHU-Specification-1505220-16-Latest-Edition1.pdf

Never mind I was gong to say something about it but this is the AWOS..  ](*,) I had this one.
« Last Edit: July 15, 2017, 03:03:16 PM by ValentineWeather »
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Online jgentry

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Re: ASOS visit with VP2 in hand
« Reply #69 on: July 16, 2017, 03:23:01 PM »
Davis Vantage Pro2. SHT-75. WU: KXALJEMI2 & KALTHORS2. CWOP/APRS: C6353 & E6358

  

Offline ValentineWeather

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Re: ASOS visit with VP2 in hand
« Reply #70 on: July 16, 2017, 05:49:07 PM »
Humm..Interesting they keep changing the longer sensor has been out. I do remember they mentioned these are initial specs when the sensor came out new.
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Online jgentry

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Re: ASOS visit with VP2 in hand
« Reply #71 on: July 16, 2017, 06:16:28 PM »
Humm..Interesting they keep changing the longer sensor has been out. I do remember they mentioned these are initial specs when the sensor came out new.

And I noticed that in the analog sheet, there is no SHT 35, just the SHT 30 & 31.
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Offline kcidwx

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Re: ASOS visit with VP2 in hand
« Reply #72 on: July 18, 2017, 10:57:20 AM »
One thing that seriously concerned me with these SHT31 evaluation boards was the long term shift in accuracy on the humidity side. I only test a particular type of sensor in minimum groups of three. When a sensor company is wanting to bid on a government contract it's usually pretty easy for me to secure at least three for testing. Although that's not the case with these evaluation boards, it was more for my own curiosity. The issue is approximately 3 weeks after receiving all three of these evaluation boards, I ran a test at 50% RH. All three were reading low by -1.2%, -1.7% and -1.9%. Almost a year later they were reading +0.5% to +0.8%. I'm at a loss to explain why the large shift over time. I'm not quite ready to call it "drift" because that's an insane amount of drift. I was so concerned, I sent my NIST reference instrument back to Washington D.C. to get it certified again after it was just certified 6 months before. It came back having tested just fine. In the hundreds of sensors I've tested over 20+ years, I never seen this much shift before over the course of a year. I was thinking of getting a fourth one and seeing how it compares right out of the box against these three units that have been running for almost a year. Some sensors do require a conditioning period when first used or what I refer to as exercising the sensor. I know that with some sensor manufacturers when they send you a sample for evaluation, sometimes these are not their best spec'ed sensors. Often they are sensors that are usable but don't quite pass QC 100% for some reason. I wonder if that's what these evaluation boards are. I never did ask Sensirion. The only thing I can think of is since these SHT31 sensors don't have a filter over them, they have become contaminated with dust over time.
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Offline ValentineWeather

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Re: ASOS visit with VP2 in hand
« Reply #73 on: July 18, 2017, 11:22:37 AM »
One thing that seriously concerned me with these SHT31 evaluation boards was the long term shift in accuracy on the humidity side. I only test a particular type of sensor in minimum groups of three. When a sensor company is wanting to bid on a government contract it's usually pretty easy for me to secure at least three for testing. Although that's not the case with these evaluation boards, it was more for my own curiosity. The issue is approximately 3 weeks after receiving all three of these evaluation boards, I ran a test at 50% RH. All three were reading low by -1.2%, -1.7% and -1.9%. Almost a year later they were reading +0.5% to +0.8%. I'm at a loss to explain why the large shift over time. I'm not quite ready to call it "drift" because that's an insane amount of drift. I was so concerned, I sent my NIST reference instrument back to Washington D.C. to get it certified again after it was just certified 6 months before. It came back having tested just fine. In the hundreds of sensors I've tested over 20+ years, I never seen this much shift before over the course of a year. I was thinking of getting a fourth one and seeing how it compares right out of the box against these three units that have been running for almost a year. Some sensors do require a conditioning period when first used or what I refer to as exercising the sensor. I know that with some sensor manufacturers when they send you a sample for evaluation, sometimes these are not their best spec'ed sensors. Often they are sensors that are usable but don't quite pass QC 100% for some reason. I wonder if that's what these evaluation boards are. I never did ask Sensirion. The only thing I can think of is since these SHT31 sensors don't have a filter over them, they have become contaminated with dust over time.

Yes, well over the claimed drift on spec sheet.
Maybe it's time to ask Sensirion for a response.
Randy

Offline kcidwx

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Re: ASOS visit with VP2 in hand
« Reply #74 on: July 18, 2017, 01:55:29 PM »
I got in contact with them. I'm waiting to hear back from the engineer however I was asked if I was testing using the EK-H4 system. I told them I have one of those but didn't realize it worked with the SHT31's. I used it with the SHT2x and SHT7x sensors. So now I have a box of board mounted SHT31's coming.

I'll test them with the EK-H4. I have all this free time now and still can't get away from this stuff.  :lol:

https://www.sensirion.com/en/environmental-sensors/humidity-sensors/evaluation-kit-ek-h4/

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