QGroundControl shows positive air speed without wind (SDP3 sensor)


I hope that this is known thing and someone suggest a solution. My airspeed sensor shows 5km/h without wind (in my room).

I spent decent time debugging this thing. Here is details.

My setup has pixhawk 4 from Holybro with PX4 autopilot v1.12.3 and SDP33 airspeed sensor from Drotek.

The sensor is connected via i2c. It is discoverable using i2cdetect command. Therefore I assume that the issue is not related to connectivity.

Sensor health
I checked the sensor by connecting it to Arduino and read raw sensor values using Sensirion example.

Raw output:

DifferentialPressure[Pa]:0.00 Temperature[°C]:26.55
DifferentialPressure[Pa]:0.00 Temperature[°C]:26.55
DifferentialPressure[Pa]:0.00 Temperature[°C]:26.53
DifferentialPressure[Pa]:0.15 Temperature[°C]:26.54
DifferentialPressure[Pa]:0.25 Temperature[°C]:26.57
DifferentialPressure[Pa]:0.10 Temperature[°C]:26.57
DifferentialPressure[Pa]:-0.05 Temperature[°C]:26.58
DifferentialPressure[Pa]:-0.10 Temperature[°C]:26.57
DifferentialPressure[Pa]:8.05 Temperature[°C]:26.56
DifferentialPressure[Pa]:36.30 Temperature[°C]:26.58
DifferentialPressure[Pa]:99.40 Temperature[°C]:26.58
DifferentialPressure[Pa]:115.85 Temperature[°C]:26.63
DifferentialPressure[Pa]:45.05 Temperature[°C]:26.57
DifferentialPressure[Pa]:41.90 Temperature[°C]:26.59
DifferentialPressure[Pa]:0.00 Temperature[°C]:26.63
DifferentialPressure[Pa]:0.00 Temperature[°C]:26.61
DifferentialPressure[Pa]:0.00 Temperature[°C]:26.60
DifferentialPressure[Pa]:0.00 Temperature[°C]:26.60
DifferentialPressure[Pa]:0.00 Temperature[°C]:26.62
DifferentialPressure[Pa]:0.00 Temperature[°C]:26.62

It shows shows 0.00 for differential pressure when the sensor is still. And shows not zero when I blow to the pitot tube. Therefore I think that the sensor function well.

I followed the manual AirSpeed Calibration | PX4 User Guide and calibrated the sensor several times to compare calibration result.
Sometimes after calibration QGroundControl shows -5km/h. in this case autopilot marks the sensor as not calibrated after restart.
Sometimes QGroundControl shows 5km/h. I expect to have 0km/h. I played with various parameters to find a way to negotiate this, but this was unsuccessful.

Probably I did something wrong. I appreciate any help. I have no idea how to resolve this situation.

Thank you,

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