Airspeed and Accelerometer

ArduPlane
#1

Hi, When I connect a Matek ASPD-7002 airspeed sensor to the F765-WING, the horizon level starts to drift slowly from left 20% to right 20% and back (controller is still on the bench). Is this normal? Should the airspeed sensor affect the accelerometer? The airspeed sensor has not yet been calibrated, so the reading is incorrect, about 200 km/h in still air, but why it influence at all?

Can I use airspeed sensor without ground station? As I know only way to do Preflight Calibration is from Mission planner. I don’t have computer in the field. Is it mandatory before every flight?

#2

Video:


Airspeed sensor connected at 11 sec.

#3

it’s not the airspeed sensor affecting your accelerometer, it’s a way off airspeed reading on an unhappy EKF (no GPS fix), which will necessarily give unuseable results trying to fuse the available data into an attitude estimate. see https://ardupilot.org/dev/docs/ekf2-estimation-system.html for reference

calibrate your airspeed sensor, test with a sufficient GPS fix (free sky view) and you’ll most likely find your horizon nice and stable.

1 Like
#4

Thank you for the explanation basti

#5

Of course you can use an airspeed sensor without a ground control station:
https://ardupilot.org/plane/docs/airspeed.html#calibration

You have to distinguish the offset calibration from the ratio calibration. The latter is performed once with a measurement flight (https://ardupilot.org/plane/docs/calibrating-an-airspeed-sensor.html?highlight=airspeed#calibrating-an-airspeed-sensor) .For safety reasons set ARSPD_USE to 0 until the ratio calibration is correct(https://ardupilot.org/plane/docs/parameters.html#arspd-use-airspeed-use ). The offset calibration is normally done automatically at each initialization. Therefore the pitot tube must be protected from wind during boot process (only the SDP33 with a non-barometric measuring method needs no offset-calibration).

I wish you success
Rolf

1 Like
#6

Thank you for good explanation Rolf.
I found the reason why I had completely wrong readings from the airspeed sensor - I first connected the controller to the PC, then to the battery, so the sensor was powered after initialization.