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From: Jeff Liebermann <jeffl@cruzio.com>
Newsgroups: rec.bicycles.tech
Subject: Re: Garmin Edge 830 elevation issues
Date: Sun, 04 Aug 2024 09:09:07 -0700
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On Sun, 04 Aug 2024 10:44:55 GMT, Roger Merriman <roger@sarlet.com>
wrote:

>Jeff Liebermann <jeffl@cruzio.com> wrote:
>> On Thu, 1 Aug 2024 21:36:41 -0000 (UTC), Ted Heise <theise@panix.com>
>> wrote:
>> 
>>> I do wonder if the thing got too wet when riding in the rain a few 
>>> days ago, and is getting gradually better as it dries out.  Who 
>>> knows.
>> 
>> That's a good possibility:
>> 
>> "Rain and moisture has serious detrimental effect on 830"
>> <https://forums.garmin.com/sports-fitness/cycling/f/edge-830/194977/rain-and-moisture-has-serious-detrimental-effect-on-830>
>
>That seems to be confused, the displayed gradient across all devices be
>that Garmin or otherwise tends to lag to some degree ie it’s generally not
>accurate, particularly noticeable across short sharp climbs where the 20%
>will display after it starts to ease off.

I don't understand what you're saying.  The failure mechanism is
rather simple, assuming the Edge 830 uses some type of MEMS (Micro
Electro Mechanical System) pressure sensor:
<https://www.sparkfun.com/categories/120>
<https://cdn.sparkfun.com/assets/0/c/d/5/3/bmp384-datasheet.pdf>
There are many variations in the sensor.  For example, the BMP384
above uses a gel filled cavity to reduce the effects of condensation
and contamination.  I have no idea what's actually inside the Garmin
830.  None of them are "water proof".

When the altitude (air pressure) readings begin to lag behind the
actual altitude, that the first sign of condensation inside the
sensor.  The sensor is something like a tuning fork, which is
deflected by the differential air pressure where one side of the fork
is inside a sealed enclosure, while the other side is exposed to the
atmosphere.  Add a tiny drop of water to the atmospheric side and the
vibration frequency changes, which changes the indicated atmospheric
pressure.  However, the sealed box might be genuinely hermetically
sealed or it might have a tiny hole in the box which leaks air to
re-establish a reference pressure over a long period of time, such as
a few days.  I suspect this is the way Garmin does it because the
instructions demand that the user re-calibrate the altimeter before
the start of every ride.

The reader comment at:
<https://forums.garmin.com/sports-fitness/cycling/f/edge-830/194977/rain-and-moisture-has-serious-detrimental-effect-on-830/1312133#1312133>
provides a clue.  The author cycles the air pressure with a vacuum
food box until the altitude delay problem magically went away.  What
he did was pump out whatever water vapor or condensate had collected
inside the Edge 830.  Heating, to promote evaporation or cooling, to
reduce relative humidity, can also be used to remove water. Installing
a desiccant bag inside the case would probably have prevented the
problem:
<https://www.google.com/search?q=desiccant+bag&tbm=isch>
Replace every one or two years or heat dry the bag:
<https://www.roycopackaging.com/blogs/news/a-step-by-step-tutorial-on-how-to-dry-a-desiccant-bag>
Desiccant is also useful for preventing corrosion.

>Bad news travels fast, I’d not chalk up much with folks on internet having
>problems, if it was a known big problem I’d expect to see it mentioned
>within the upgrade 840/540 over the 830/530 folks like
><https://www.dcrainmaker.com> who do highly detailed reviews and potential
>issues that come up.

DcRainmaker.com is a really good site for evaluating bicycle
electronics and gizmos:
<https://www.dcrainmaker.com/2019/04/garmin-edge-830-cycling-gps-in-depth-review.html>

As for news traveling fast, that's true.  However, solutions, theories
and fixes don't appear anywhere near as fast when there is little or
no technical information available from the manufacturer.  For
example, when I was looking for a photo of the inside of an Edge 830,
all I could find was the iFixit teardown, which showed very little.
Oops, I didn't notice that there were several 830 teardowns on the
iFixit site.  This one shows a little more internal detail but nothing
that would help me find or identify the air pressure sensor:
<https://www.ifixit.com/Guide/Garmin+Edge+830+Battery+Replacement/149237>

>Ie I’m sure it’s possible but I’m cynical that it’s a know issue as you
>where.

My experience with Garmin products goes back to 1992(?), when I found
myself dealing with the company and their products in both the
avionics and marine sector.  My actual involvement in those days was
minimal, but was a sufficient excuse to buy an early Garmin GPS-50
which was sufficient for learning something about how GPS works:
<http://retro-gps.info/Garmin/Garmin-GPS-50/index.html>
(Mine was for marine use using the same electronics but with a panel
mount enclosure).

I don't want to unload my experiences and disappointments with Garmin
and their products.  Sufficient to say that I'm generally disappointed
with Garmin and some of their products and support.  Yes, that's
cynical, but then I'm usually cynical with all companies and products
until they demonstrate otherwise.

>> It's possible to "pump" water into an allegedly waterproof enclosure.
>> Heat the GPS with hot air to about 45C.  Then dump it in a bucket of
>> 10C cold water.  The air inside the GPS will contract and create a
>> partial vacuum, which then sucks the water into the enclosure (if
>> there are any leaks).  Look for condensation INSIDE of the enclosure
>> and intermittent button press failures. 
>> 
>> Most consumer GPS products can survived one or two heating and dunking
>> cycles without difficulty.  The units that I tested in the mid 1990's
>> were horrible.  None of them survived more than about 10 heating and
>> dunking cycles.  After failure, none of them recovered by themselves
>> as there was no path for the water vapor to exit the enclosure.  I had
>> to disassemble all the test units and hot air dry them.  (Hint:  Rice
>> doesn't work).
>> 
>> The Edge 830 has a IPX7 water rating:
>> <https://www8.garmin.com/manuals/webhelp/edge830/EN-US/GUID-CE2FC337-A232-482C-8747-A49C0098962E.html>
>> <https://www.garmin.com/en-US/legal/waterrating-definitions/>
>> "IPX7 - Withstands incidental exposure to water of up to 1 meter for
>> up to 30 minutes.  Suitable for: splashes, rain or snow, showering"
>> 
>> In other words, forget about submerging it in a bucket of water even
>> though the spec hints that it can be done.  That also includes a
>> puddle of water on the faceplate, standing water on the faceplate
>> caused by a front bezel that creates a pond, or standing water on any
>> joint in the pastic case.

>The bezel is flat no ridges so water will not pool but be drops though
>don’t use the silicone case which I guess might make it pool marginally
>more, only problem with rain is the touch screen but one can lock that, and
>generally i certainly don’t touch the device much once started.

Yes, a silicone case will collect water and is probably a bad idea in
a wet environment.  However, it's a good addition if there's any
danger of dropping the Edge 830 on hard pavement.

>> If you suspect that water is the culprit, my suggestions is to open
>> the Edge 830 case and let it dry out.  Hopefully, that will help it
>> recover.
>> 
>> Sorry about not answering your question earlier.  I had no idea what
>> was causing the problem and didn't think of water incursion until you
>> mentioned it.
>> 
>> Good luck.
>
>Roger Merriman
>
-- 
Jeff Liebermann                 jeffl@cruzio.com
PO Box 272      http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann      AE6KS    831-336-2558