Author Topic: Texas Weather humidity senor  (Read 920 times)

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Offline s435weather

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Texas Weather humidity senor
« on: September 17, 2021, 12:20:14 PM »
Has anyone tried to repair their Texas Weather Station? I own a Wps-10 that has run for over 20 years with just a few minor issues that were fixed. The humidity sensor no longer reads correctly. Would anyone know or have a list of vendors used for sensors on the now out of business weather station? The sensor looks like an easy repair if I could get hold of a new one.

Thanks

Offline dupreezd

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Re: Texas Weather humidity senor
« Reply #1 on: September 17, 2021, 01:09:52 PM »
See this post, there is reference to sensors.

https://www.wxforum.net/index.php?topic=40989.0
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Offline DaleReid

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Re: Texas Weather humidity senor
« Reply #2 on: September 17, 2021, 03:45:20 PM »
I would echo that  Kev, mentioned in the link to another thread, has done a bit of work getting this documented.

Another forum contributor, whom I do not recall the name, has said that he has taken his sensor apart and replaced the humidity sensor three times or so.

The Honeywell sensor is available from DigiKey and others, less than $20 the last time I looked.

On my board I had a thick coating of a flexible conformable water protectant.  It took a bit of very careful work with tough very sharp small scissors to snip away to get to the solder points.  The stuff was more like SprayLat on desert stored aircraft than it was the hard clear conformational coatings I've seen on other boards. 

I am no expert on this, so TWI may have used different coatings at different times on their sensors.   Apparently the sensors come with calibration points, or used to.  The reason I'm a bit uncertain is there was a dealer in Florida who was selling out the stuff he had, and actually made an alternative board, one which uses a fixed voltage source feeding one of the newer humidity chips, and the factor there was fixed.  I'm not sure if all the new sensors come with a much more predictable setting or not to enter into the 0% and 75% humidity calibration points on the TWI control boards.

Again, Kevin has some rough sketches of the boards and even some info on the alternative boards.  I'm not sure if the dealer in Florida is still on line or not or has sold everything out.  You might search eBay for TWI, and the last I saw he was selling a tipping bucket rain gauge from them along with a few other things.  You could see if he still has a presence on eBay and contact him to ask if he has any of those boards left. 

Good luck and to keep these old systems going, please ask if you don't get everything up and running.
Dale
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Offline s435weather

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Re: Texas Weather humidity senor
« Reply #3 on: September 17, 2021, 04:33:15 PM »
Thanks to you both on all this information, this is fantastic news, I did not really think anyone would of kept track of these "deserted" units so close.  I will order the sensor and give it a try. At some point I do have to give up on my old faithful weather station, it has been great all these years. Thanks again. I will keep you updated after I install to see if my humidity is back again.

Offline s435weather

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Re: Texas Weather humidity senor
« Reply #4 on: September 21, 2021, 09:57:09 PM »
So waiting for my recent order of a new humidity sensor for my TWI station,  I noticed that my dew point was actually reading correctly, but humidity was reading 0% which at the time of morning was more like 65%.  Could it possibly be that my humidity sensor is working but the problem might be with one of the boards instead?

Thanks

Offline DaleReid

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Re: Texas Weather humidity senor
« Reply #5 on: September 21, 2021, 10:35:58 PM »
The dew point is calculated, not measured directly as far as I know (and understand how a Vaisala dewpoint detector works.)

Can you watch the humidity for a few days to see if it tracks and compares to a local station (as good as it can be expected)?

Can you tell me where you are getting the dewpoint from?  On the console somewhere or in reporting from an external data proram?
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Offline s435weather

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Re: Texas Weather humidity senor
« Reply #6 on: September 22, 2021, 09:18:15 PM »
I made several comparisons today, the humidity sensor was way off most of the day. The dewpoint does look calculated but appears to have default limits when the humidity is way off like 0, when it should be 80, dew point defaults to current temperature.

I decided to start taking it apart. There is quite a lot of that white sealant like what was mentioned in an earlier post.  I am assuming the humidity gauge is inside the black tube?  Is it really possible to cut away all that white sealant? It feels really hard. Any tool recommended? A sharp small scissors?


Offline DaleReid

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Re: Texas Weather humidity senor
« Reply #7 on: September 22, 2021, 10:09:57 PM »
AS old as these sensors are you are probably correct in assuming the humidity sensor is kaputz.
I'd advise to ONLY cut away the white stuff on the humidity sensor, and leave the rest be.  I spent hours with a nice tiny but really sharp (dissecting type) scissors and sometimes made little progress.  I was doing the whole board to get an idea of what the circuit did and how it was all connected, so I did try to take the whole thing off.

You only need to get the humidity sensor open and enough showing to solder the legs of the new one to the stubs of the old one; I'd advise initially against trying to expose enough to desolder through the board and on the back, although that is idea if you have the skills and tools to do it. 

I'd take the 'easy' way first and just carefully expose and clean, then even add a bit of electronic grade rosin (not plumbing!!) to the newly cleaned legs and get a good joint on each one of the three legs.

Take a picture and send it along. 
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Offline s435weather

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Re: Texas Weather humidity senor
« Reply #8 on: October 24, 2021, 09:35:53 PM »
I have some good news on my TWI humidity sensor.
I ended up cleaning off much more of the white sealant on the board and found out one of the legs of the new humidity sensor I had previously soldered had broken by the base of the board. After soldering in a new small post to the board and re-soldering on the humidity sensor the humidify sensor is working great.

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Offline DaleReid

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Re: Texas Weather humidity senor
« Reply #9 on: October 24, 2021, 10:13:02 PM »
Great news.
Be sure to put some sort of light protecting tube over it. I'm not sure about re-coating the board with some conformal material.  I know there is a product that Digi-Key has that can be painted on to reseal the board.

Congratulations on saving another temp/humidity sensor.  You'll inspire me to get mine fixed.
Dale
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Offline s435weather

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Re: Texas Weather humidity senor
« Reply #10 on: October 24, 2021, 10:39:40 PM »
yes, it had a light protecting tube that I tool off originally. I added it back on when I added the 388 Electronic grade silicone to cover back up the exposed board. I hope that seals it back up good.

Offline DaleReid

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Re: Texas Weather humidity senor
« Reply #11 on: October 25, 2021, 07:49:55 AM »
You are way ahead of us!  Thanks for keeping these old but usually reliable stations up and running.  Dale
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