Topic: THGR968 - temp below -10c / 14F

[mackbig]

Anyone out there still using the stock THGR968... and have a current temperature under -10C / 14F????
Cant recall does that sensor suffer from the -10 no humidity change bug?

Andrew

[Downlinerz2]

Andrew,
   I don't use the stock THGR 968 sensor but it is hooked up and reading.  Mine went down to -15.7F at 7:40 am.  The 122NX sensor bottomed out at -11.9F.
On my VWS I graph both of the humidity sensors to see how they compare.  At first I thought they were fairly close.  But I then realized the grid on the right side was much lower than the other.  My graph shows that since the 14th the 122Nx sensor has measured humidity at 89%.The 968 is at approx 55% .  Neither has showed much change on the graphs.  Using these graphs really showed me the difference in these two sensors.
                                                     Mark
                                           

[mackbig]

Mark,
I thought it was also affected, but could not recall.   I had forgotten about this "feature" until I noticed my "stuck" sensor on madis.

My humidity has been stuck at 57% since 6pm on jan 13.  Looks like I will unstick tomorrow when the high hits -8c.

Even the "extreme cold weather" sensor has this bug. There was a discussion and I had done some testing with my shack sensor and base in the freezer, but the results were lost with the demise of the ambient forum.

Someone had commented that humidity is not accurate below a certain temp anyway, but since most other stations and official metars keep reporting it, it is still valid to me.  Not sure what they were thinking when they made it work this way. 

From recollection the display on the sensor keeps showing the "new" humidity but the xmit function stops working (could be wrong about that though to.  I do know the second it hits -9.9 a new and vastly different humidity reading shows up on the console.  I will test that theory with an extra sensor tonight.

Andrew

[Downlinerz2]

Andrew,
   It has been very interesting to follow the humidity graphs of these two sensors.
I may not have noticed that the humidity has remained unchanged since the 14th if not for these graphs.  I am really new to the weather hobby. At temperatures this cold, would the changes in the relative humidity vary by much since there is so little moisture in the air?  I can't wait now to see how the graphs go as the week goes on and we warm up a bit.  I think by the middle of next week we are supposed to go into the 30's here in NW Ohio.  Can't wait so my wind gauge can thaw too.                                   Mark

[mackbig]

Even at these temps there are fluctuations in RH.   Check out my cwop graphs, compared to the metar which is on 2kms due west of me.  You can see it a bit on the dewpoint graph, but the blue flatline on the last graph for RH really shows it...

Andrew

http://weather.gladstonefamily.net/qchart/C8618?date=20090116&addnl=CYKZ&Add+to+charts=Add+to+charts&.cgifields=addnl

[mackbig]

when the temp hits -9.9c (14.18F) you will see either a spike or a dip.   Small chance the RH might actually be at a similar level as when it breaches -10 depending on how fast the drop was, or time of day, other conditions.

Here is my page from Jan 12, the last time it went above -10.   between 8 and 8:20 the temp hit above -10, the humidity instantly registered 21% higher going from 60 to 81%

Andrew

http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=IONUNION1&day=12&year=2009&month=1

[Anthony]

With mine humidity stops updating at or below 14F. Mine remains at what ever the humidity was when the temp hit 14F. And dew point displays LLL.

[Downlinerz2]

Andrew and Anthony,
  Those graphs are very good.  I am going to be taking a longer look this evening.
Both of my sensors went flatline at the same time on the 14th.  the 122NX did show a small, about 1%, about 24 hrs later.  That dip coincided with the start of the steep decline in temperature that started yesterday afternoon and evening.  As you say Anthony, my sensor went flat, on the 14th, at a temperature close to 14F.  I too get the LLL.  I have seen that many times recently but did not pay much attention to it.  Thanks to you both.  I have learned much today from you .  Ignorance is not bliss when it comes to the weather.
                                                   

[sam2004gp]

Weird, both my THGR968 Humidity and the Channel 1(Radio Shack extra sensor) Humidity flat lined when they got under 14F.  But so far today I have had 4.1 as my low.

[Sawdust]

Curiouser and curiouser.   My WMR968 flat lined at temp of -9.94...for about 4 hours.   Then, when temps got above that level, it started recording just fine.   Some other local weather stations using other hardware, were reporting down to -15 to -19.  I checked the manual, and the official range is listed as a low of -4.  So I guess anything less probably should be considered a bonus.  Is that an actual bug?  or a limitation on the technology?

[Downlinerz2]

Hi again,
   I had a friend here a little while ago reading some of these posts and he got the impression I was saying that both temperature and humidity stopped updating.  So, I better just make sure that I meant that my humidity readings went flat while my temperature readings kept reporting all through the night and morning and bottomed out at: -11.9F.  Sorry if I was not clear in my post. 
   All through today my humidity reading has not changed from 85% with a high temperature of: +5F. It's 9:30pm now and it is:-4F.

[mackbig]

Concur with Mark.  I am only talking about humidity.  My temps are accurate, and tracking with metar right down to minus 25.5 (-13.9F) the other night.   Andrew

[Anthony]

I knew that both of you were takking about the humidity and not the temperature. It's to bad that there is not way to force VWS to use the humidity from the metar when our temps get below 14. But it seems like I read that below a certain temp humidity doen't mean that much. And when you think about it. The humidity is usually quiet low during extremely cold weather.

[Downlinerz2]

Anthony,
  I couldn't agree with you more! 

[mackbig]

Anthony my clarification was for Sawdust, knew you knew etc.....

I agree, but I still dont know what they were thinking in the first place.  Was it just an oversight that propogated from os to the radio shack versions and was never fixed, or was it intentional...  And if it is just in the sensor from an xmit point of view why did they not address in the new 122 123 versions.

This was one of the 2 or 3 emails I sent to os way back when that were never responded to....

Andrew