Barometer reading issue


I started to test the barometer and the readings are unstable. I installed the real time kernel for RPi 1 and run the Barometer example provided in Docs section. I did the test inside and here is what I got:

pi@raspberrypi ~/Navio/C++/Examples/Barometer $ sudo ./Barometer
Temperature©: 25.924917 Pressure(millibar): 1007.512451
Temperature©: 25.882750 Pressure(millibar): 1007.472473
Temperature©: 25.893848 Pressure(millibar): 1007.498840
Temperature©: 25.895134 Pressure(millibar): 1007.492981
Temperature©: 25.899263 Pressure(millibar): 1007.507507
Temperature©: 25.909214 Pressure(millibar): 1007.503357
Temperature©: 25.915644 Pressure(millibar): 1007.522278
Temperature©: 25.925255 Pressure(millibar): 1007.510132
Temperature©: 25.923901 Pressure(millibar): 1007.525696
Temperature©: 25.929453 Pressure(millibar): 1007.519531
Temperature©: 25.932972 Pressure(millibar): 1007.468018
Temperature©: 25.936966 Pressure(millibar): 1007.479919

I read that it could be linked to power supply so I tried two different power sources (usb and power module) but it gave the same results.

Any idea of what could be wrong?

What is unstable?


It is the pressure. I agree that it seems pretty stable but converted into altitude, it gives variations up to 50cm whereas barometer datasheet announces a precision of 10cm. In the example on emlid site, there is a variation of 11cm and it is in line with an another example of use of this sensor I found on web.

The ms5611 is quite sensitive. You need to cover it to reduce direct air and light exposure. Its a standard practise with apm, pixhawk, navio, etc. Read the Ardupilot/APM Copter wiki for details. Almost everything in there applys to the navio. If you want really dialed in baro readings it’s time to make a static/pilot tube :smile: have fun