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justinchuby / barometer-project

Issues repository for Barometer
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Faulty pressure reading on both phone and watch app at ~2bar ambient pressure #7

Open ajmcc opened 11 months ago

ajmcc commented 11 months ago

I'm taking hyperbaric oxygen therapy, whereby I breathe pure O2 at an ambient pressure of ~2bar for 90 minutes in multi-seat pressure chamber. Previously I've used an Android phone with a barometer app to monitor the pressure, but as I've recently switched to iPhone 13 and an Apple Watch Ultra, I would like to use these instead. I've installed the Barometer app on both iPhone and watch, and today I did some testing. Sadly I found both devices to be reading way out, with an ambient pressure of ~2 bar, which was shown correctly on the Android barometer app on a Pixel 3a. The readings on the Apple devices were as follows:

Android phone (Google Pixel): random Play Store Barometer app: 2028mbar Watch: Apple way finder watch face: -19,250FT (= ~1947mbar = 'near enough') Watch: Barometer app: 1494mbar iPhone: Barometer app: 1310mbar

Pics attached.

I should add that what I observed, was during the 'descent' to 2bar pressure, the Barometer app was reading more or less correctly, but then 'maxed-out' at the readings shown. Similarly, on the 'ascent', the watch and iphone remained stuck at the faulty readings, until the ambient pressure dropped to those values whereupon they started to show the expected pressure as it decreased to ~1bar.

Clearly the Barometer app is broken in some way and not fit for this purpose unless it can be fixed ???

IMG_0125 IMG_0127 PXL_20230718_084422987

justinchuby commented 11 months ago

Thank you for reporting this issue! I wonder if Apple compensated the barometric readings in some ways when it is calculating the altitude, as this is what needs to be accurate for them. The pressure number in Barometer is a direct readout from apple’s API so I am wondering if that alone if not accurate enough.

justinchuby commented 11 months ago

As you observed the numbers were trending correctly until they max out. I wonder if it means it has reached the limit of the sensors? I will research more on this.

There are also other barometer apps on the App Store. Do they produce the same readings?

ajmcc commented 11 months ago

The Apple altitude complication on the fancy (Wayfinder) watch face shown in one of my pics, does show a plausible reading of -19,250 feet at ~2000mbar, so the data does appear to be there. And the watch itself is designed to support diving down to some extreme depths, so I believe the sensor and supporting API should easily be capable of 2000mbar.

I will do some more testing with other apps and feed-back. My next session in the chamber is on Friday. Cheers, Andy