Author Topic: Replacing probe in a Davis temperature/humidity station.  (Read 124 times)

elagache

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Replacing probe in a Davis temperature/humidity station.
« on: February 16, 2021, 11:12:45 pm »
Dear WeatherCat station caregivers,

Recently, I noticed the batteries in my auxiliary temperature/humidity station were being consumed faster than in the past.  The first instance was only about a week earlier than usual.  However, a week later I once more got a warning on my console:



Yes I know that would appear to be my ISS transmitter, but I moved that to transmitter ID #2 and instead put the temperature/humidity station as ID: #1

Returning to our story, this definitely started to look like da' dreaded ISS battery "eatin'" syndrome that I ran into a few years ago:

https://athena.trixology.com/index.php?topic=1434.0

I never found a definitive explanation, but the one likely culprit was that I had spliced an extension to the temperature/humidity probe as can be seen in this photo:



It turns out these probes are very sensitive to splices and/or long cables.  So it appeared to be time to replace the temperature humidity probe itself.  I decided to use my economic stimulus and purchase a probe from Scaled Instruments:

https://www.scaledinstruments.com/shop/davis-instruments/parts/vantage-pro2-parts/temperature-and-humidity-sensor-parts/davis-7346-070-pro2-digital-temperature-humidity-sensor-sensiron-sht31/

This newer part isn't exactly compatible with my older transmitter.  However, it should have been easy to calibrate so the temperature would read correctly.  Alas, da' plot would eventually thicken.

As can be seen in the photo above, the temperature/humidity station was very dirty and neglected.  Here is a close-up of the radiation shield:



The greyish color comes from the wildfire ash that had deposited on the components and was never removed because this location is protected from rains.  Here is a photo of the radiation shield dismantled which shows the ash even better:



This photo also shows the protracted cable which I had spliced all the way back in 2010 (in my ignorance.)

The new probe screws into exactly the same mounting holes on the radiation shield plate:



Now all that was left to do is reassemble the radiation shield:



A reasonably obvious trick is to secure one screw in order to align the stack of plastic plates.  That makes the subsequent installation simpler.  At last I plugged the new probe into the old transmitter:



Finally, here is an overall view of the completed repair:



All that was left to do was to recalibrate my recievers to correct for the fact this sensor reads 0.9˚ F high.  Thanks to the manual, this was simply done on my console.  Alas, I use a Weather Envoy to receive data for my Mac. 

The only way to change settings on a Weather Envoy is to use WeatherLink software from Davis.  As most of us Davis owners know, WeatherLink Mac is - shall we say - a bit too minimalist in its functionality.  For starters, I tried to launch my old copy of WeatherLink on my Mac mini only to see the usual error associated with launching it as a 64-bit application.  When I tried to correct this - I couldn't!  Already on Mojave, Apple had removed the option to launch in 32-bit mode!

Fortunately, I still have my old MacBook Pro that I use for adjusting the electronic fuel injection parameters on my trusty wagon.  It is running macOS 10.9 (Mavericks.)  It took some horsing around, but eventually I got WeatherLink Mac running there and connected to my Weather Envoy.  When I finally could attempt to calibrate the probe - I couldn't!  Alas, WeatherLink Mac doesn't have the functionality to adjust anything more than the ISS external temperature probe and the Envoy internal temperature probe and barometric pressure.  So after all that effort, I couldn't calibrate the probe as the data is fed into WeatherCat.

As it turns out, I don't really use the data for anything, so I'll just leave things as they are for now.  However, if someone has a clever idea of how I can calibrate this probe on my Weather Envoy - by all means do suggest!

There is one last bit of the tale to be told.  Once the new probe was installed, I left the battery that was accused of low-voltage.  The console stubbornly insisted the battery was weak even after 24 hours, so I investigated.  Under load the battery reported a somewhat low voltage of: 2.98.  This is precisely the sort of bizarre behavior I observed during those dark days of the "battery eatin' syndrome."  I put a fresh battery which I checked was at 3.25 Volts.  I hope that my problems are finally behind me but of course . . . . . only time will tell!!

Cheers, Edouard  [cheers1]

xairbusdriver

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Re: Replacing probe in a Davis temperature/humidity station.
« Reply #1 on: February 16, 2021, 11:27:39 pm »
Exactly because problems are behind you is why they often bite your derrière! [headbang] [rockon]

Not sure from your details but did you have to do the splicing again?! :-\

Blicj11

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Re: Replacing probe in a Davis temperature/humidity station.
« Reply #2 on: February 16, 2021, 11:57:25 pm »
Another well-related tale Edouard, complete with photos. Thanks for taking the time.
Blick


elagache

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I HATE reruns . . . . . (Re: Replacing probe in a Davis station.)
« Reply #3 on: February 17, 2021, 11:19:50 pm »
Dear Blick, X-Air, and WeatherCat station caregivers,

Another well-related tale Edouard, complete with photos. Thanks for taking the time.

In those immortal words of W.C. Fields:  "This is only the beginning!"

Exactly because problems are behind you is why they often bite your derrière! [headbang] [rockon]

 ;) . . Do you have to be so "blankety-blank" prophetic?  [banghead]

Not sure from your details but did you have to do the splicing again?! :-\

No splices were required or made - so I'm innocent as far as that is concerned.  Alas, this morning I found on the Davis Console:



Sorry, the image isn't as sharp as the first one, but you can make out the low battery warning on station #1.  Note indeed the date.  I replaced this battery on Monday - and . . . . . .  :o

I took my super-deluxe Fluke multitester and . . . . . . *Heavy Sigh* . . . . . under load, the voltage was 2.99.  I tested the battery before installing it and it was 3.25 Volts!!

So there can be no doubt.  I'm the victim of da' dreaded ISS battery "eatin'" syndrome! - once more.  Given that this has happened to me before I'm assuming there is something about these old spliced temperature/humidity probes that eventually damages the ISS circuit board somehow.  The damage causes excessive battery drain under some sort of conditions - perhaps repeatedly recharging the super-capacitor or something analogous.

Last time this happened, replacing circuit board solved the problem.  The same board is used in the temperature/humidity stations as the ISS itself.  Since I have done this before, I simply need to decide what to buy and get on with the purchase.  Scaled Instruments sells the circuit boards separately and buying that would save me some money.  The alternative would be to buy the whole housing and board and save myself some labor.  I need to spend some time researching the whole matter and decide which option I prefer.

Ironically this should solve my problem with the Weather Envoy getting data that is 0.9˚ F too high.  I can get a board manufactured since 2016 when Davis made the change.  That way it will transmit the correct temperature and the Weather Envoy won't need any additional calibration.

Still, . . . . . . . I hate reruns  .  . . . at least of this variety!

Oh well, . . . . . .  Edouard

Blicj11

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Re: Replacing probe in a Davis temperature/humidity station.
« Reply #4 on: February 18, 2021, 07:00:20 pm »
Well dang it, sorry. After you had your first battery eating issue and resolved it, I had something similar happen to me, with the ISS battery. Replacing the circuit board also solved my issue, but you may recall that the first replacement board I tried was bad and it took me 5 months to figure out it needed to be replaced with a replacement. Using one of your favourite quotes, "Oh well...."
Blick


elagache

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Board on its way. (Re: Davis temperature/humidity station.)
« Reply #5 on: February 19, 2021, 11:05:39 pm »
Dear Blick and WeatherCat faithful,

Well dang it, sorry. After you had your first battery eating issue and resolved it, I had something similar happen to me, with the ISS battery. Replacing the circuit board also solved my issue, but you may recall that the first replacement board I tried was bad and it took me 5 months to figure out it needed to be replaced with a replacement. Using one of your favourite quotes, "Oh well...."

Thanks for the sympathy.  Fortunately, this isn't the primary setup so I'll live with the hiccups for the moment.  Yes I do remember your own struggles with faulty ISS circuit boards.  I do hope that when Davis updated the boards for the 2016 run they might have fixed some of these issues. 

The board is in-route as I type.  I'll keep everyone posted as this soap-opera further unfolds . . . . .

As indeed seems appropriate . . . . . .

Oh well,
. . . . . . Edouard