Each time I run, after about 2.5 km, I stop for about 5 minutes for a little stretching. When I start back, and the temperature rose of about 1 degree Celsius, I noticed a drop in the elevation field. Only in recent time I noticed that the drop is increased up to over 20 meters! I’ve checked previous runs with previous FW and actually the issue was the same just I did not notice it so much since it was just a drop minor than 10 meters.
Here below the examples, all done having the option for automatic calibration on
I suppose the "Atmosphere" field on your watch is the same as the "Ambient Pressure" field on my Fenix 3. This is the signal from the ambient pressure sensor in the watch, and consequently the one to look at when looking for a hardware defect. (The Barometric Pressure and Elevation readings are software generated and can have multiple reasons for an error).
The ambient pressure reading should ideally not change with temperature. On my watch I can change the reading 0.1-0.2 millibar by cooling the watch 30 degrees. 0.2 millibar is equal to an altitude change of less than 2 meter, so I find this accuracy acceptable.
In your example, you have changed the reading 1.8 millibar by cooling the watch 16 degrees, and that is a lot. I don't know if it is typical for the 935.
Are you sure that the breathing hole for the pressure sensor is not plugged? In theory, if the hole is plugged so the pressure inside the watch cannot equalize, a cooling of the watch will cause the pressure inside the watch to drop. But this drop will be much larger than 1.8 millibar - more like 50 millibar. So the hole would have to be blocked just enough to significantly delay the pressure equalization without creating huge pressure variations, and I find that hard to believe.
I suppose that the building you stay in before the run is not pressurized. Otherwise, that might be an explanation. But 1.8 millibar is quite a lot, and you would feel that when opening the front door.
thanks AllanOlesen67 for your support and clear explanation! It helped me to better understand. Apologies I tried to translate directly from my language. I confirm you that the field "Atmosphere" is "Ambient Pressure" you mentioned (i will update the post to avoid confusion) and my building is definitely not pressurized.. So you suggest first try to wash the watch? i do not see any hole actually
So you suggest first try to wash the watch? i do not see any hole actually
I have never had the problem myself, so I don't really know. But the 935 is waterproof to 50 or 100 meter like the Fenix watches, I assume? In that case, nothing bad would happen if you put the watch in soap water for some hours.
Some F5 and F3HR owners do the soap bath frequently because the pressure sensor in those watches is sensitive to static electricity. I don't think this is your problem, but the water and soap might also clean out some debris from the opening.
The sensor is located back of watch, bottom center. Be careful not to forcefully jam anything in there as you might damage the sensor but a good bit of water might help. I've never been very happy with the 935 altitude reading and often find my activities have ridiculous gain/decent values that force me to use map data.
At 2.5 miles went inside for about 5 minutes. Inside temperature would have been around 22C and outside was -15C. You can see elevation dropped 246 feet.
Thanks for the response! The watch was exposed to a rather significant temperature change but was brief. The data file shows the watch went from reading -3C to 4C. Is that still significant?
On my Fenix 3, I have never seen elevation changes of that magnitude caused by temperature changes or from going from indoor to outdoor. An elevation change of 246 feet is equal to an ambient pressure change of approx. 8-9 millibar.
As I said earlier, I see ambient pressure changes of 0.1 to 0.2 millibar when I cool the watch 30 degrees.
But of course, I do not own a 935 so I can't know if it is more sensitive to temperature changes.
I came across this thread and I don't want to get to far off topic, but I was hoping someone can answer a question of mine. I know the difference between ambient and barometric pressure. My barometer on my watch reads 29.70 in Hg and it's 51 degrees Fahrenheit out. I checked my barometer with the Weather Underground, AccuWeather and online for McCord Air Force Base. All had a barometric reading within .01 in Hg of my watch. My watch has an ambient pressure reading of 29.27 in Hg. My question is what does my ambient pressure reading tell me other then the obvious that they are different? How do I use the two readings to benefit me in anyway?
