I can’t figure out what is going on with my MPR sensors. I have 2 and they are both reading ~12.2 PSI for atmospheric pressure, when it should be well into the 14’s. I’m using the example code with no changes. I notice on your hookup guide you have a screen shot (https://cdn.sparkfun.com/assets/learn_t … h_Text.png) that lists the “Average Pressure at Sparkfun” as 12.2 as well. I’m at a similar elevation, so this kind of makes sense. But this is way to low for atmospheric pressure, lower than the lowest ever recorded. Any chance you can shed some light on this? Is there a bug in the library code, or am I missing something simple?
Hello, I am not from sparkfun. Just a curious customer. Do your sensors response to positive and negative pressures? Do you see any changes in the reading? Or is it always showing 12.2?
They respond as you would expect to positive and negative pressures. Testing seems to indicate when I subtract out atmospheric pressure to get a gage pressure, the result is accurate. There is mention of calibration in the datasheet, but when I saw the picture in the Sparkfun example matched what I was seeing, I figured I’d ask.
12.2 PSI (24.84inHg) is perfectly normal for an altitude around 5400 feet. Sparkfun is near Boulder, CO where the altitude is roughly 5300 feet. If you’re at a similar altitude, 12.2 PSI is a perfectly reasonable value for you to be getting.
Keep in mind sensors like these give you absolute pressure that hasn’t been ‘normalized’ so they won’t match what you see on the weather report on the news. The link below might be helpful for understanding how pressure is corrected for altitude.
this is way to low for atmospheric pressure, lower than the lowest ever recorded
As indicated by YellowDog’s contribution above, keep in mind that airports and most weather services correct local air pressure readings to sea level, and that the “lowest ever recorded” will also be a sea level measurement (or corrected to sea level).
