Author Topic: Dew point problem  (Read 1540 times)

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Offline jayr027

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Dew point problem
« on: January 18, 2018, 11:47:56 PM »
Hi WXFORUM,


I am an avid fan of weather but I have a problem with this station because if consistently giving me negative values on a specific time after a long  no data every day. I am not sure on what happened on my dew point as it always giving me negative values after it missed reporting some hours. Does the problem is the operator turning it off every night? ANy ideas? please help me., BTW i am living in PHilippines so it is so impossible to have a negative values.

Offline Old Tele man

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Re: Dew point problem
« Reply #1 on: January 19, 2018, 12:16:59 PM »
Dew Point values are "derived" which means they are calculated (from Temp & humidity), not directly measured.

The system is designed for continuous operation as some variables are time-averaged. Do you have the unit powered by batteries, AC-adapter, or (better) both?
« Last Edit: January 19, 2018, 12:19:05 PM by Old Tele man »
• SYS: Davis VP2 Vue/WL-IP & Envoy8X/WL-USB;
• DBX2 & DBX1 Precision Digital Barographs
• CWOP: DW6988 - 2 miles NNE of Cortaro, AZ
• WU - KAZTUCSO202, Countryside

Offline jayr027

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Re: Dew point problem
« Reply #2 on: January 20, 2018, 05:30:33 AM »
Dew Point values are "derived" which means they are calculated (from Temp & humidity), not directly measured.

The system is designed for continuous operation as some variables are time-averaged. Do you have the unit powered by batteries, AC-adapter, or (better) both?



=They have the ac adapter but not so sure if they have batteries in it. Do you have any idea where the negative values coming from? My TL is correct and seems okay.

Offline Old Tele man

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Re: Dew point problem
« Reply #3 on: January 20, 2018, 01:30:26 PM »
Calculated Dew Points CAN have negative values, indicating they are below zero degrees.
• SYS: Davis VP2 Vue/WL-IP & Envoy8X/WL-USB;
• DBX2 & DBX1 Precision Digital Barographs
• CWOP: DW6988 - 2 miles NNE of Cortaro, AZ
• WU - KAZTUCSO202, Countryside

Offline PaulMy

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Re: Dew point problem
« Reply #4 on: January 20, 2018, 02:11:57 PM »
My station derived dew point is mostly below 0°C in the winter, but then I am not in the Philippines.
Currently: Temperature 4.5°C     Dew Point -0.1°C

Paul

Offline Old Tele man

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Re: Dew point problem
« Reply #5 on: January 20, 2018, 02:26:28 PM »
There is a simple equation for estimating Dew Point temperature from temp and RH:

http://www.wxforum.net/index.php?topic=32799.msg332571#msg332571
« Last Edit: January 20, 2018, 02:28:35 PM by Old Tele man »
• SYS: Davis VP2 Vue/WL-IP & Envoy8X/WL-USB;
• DBX2 & DBX1 Precision Digital Barographs
• CWOP: DW6988 - 2 miles NNE of Cortaro, AZ
• WU - KAZTUCSO202, Countryside

Offline jayr027

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Re: Dew point problem
« Reply #6 on: January 22, 2018, 12:47:26 AM »
Calculated Dew Points CAN have negative values, indicating they are below zero degrees.


but in Philippines, normally 30 TL and more. but never had a 0 or negative since we are living in a tropical countries. I

Offline dalecoy

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Re: Dew point problem
« Reply #7 on: January 22, 2018, 10:40:11 AM »
. Does the problem is the operator turning it off every night? ANy ideas? please help me.,

Try changing that (don't let the operator turn it off every night).  See if the problem goes away.