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Powering Issue: Pixhawk3Pro-PMU-Digital Differential Airspeed

Dear all,

I am using the following configuration Pixhawk 3 Pro, Power Management Unit (PMU), Digital Differential Airspeed. Two in series 6S LiPo batteries are used to provide power to the PMU. Pixhawk is connected to the PMU using both the “Power 1” and “Power 2” power-lines which should supply 5V. Full calibration and setup is performed on the systems. I have two identical apparatus which I have tested although I got the same results presented below. When the Digital Differential Airspeed sensor is not used, the apparatus can be armed, both the servos and the motor work. When the Digital Differential Airspeed sensor is used, the apparatus cannot be armed, the servos work, the motor cannot as the system is not armed.

The problem I am encountering is that when I power the Pixhawk module using the Power Management Unit (PMU) using the batteries, the airspeed sensor does not provide good reading. The values I read in QGroundControl fluctuate between -6 and 40 m/s. PC to Pixhawk connection using the telemetry system.

When I power Pixhawk via USB (using either the PC or an external power bank), the reading from the airspeed sensor become more stable and in a range within -2 to 2 m/s. This happens both when I read from Pixhawk using the USB connection as well as when I use the telemetry system (thus powering Pixhawk using a USB power bank). So the problem is not the telemetry system. I am wondering whether the PMU does output 5V.

Could you provide me any support?

Kind regards,

Have you tried to check the PMU 5V output for a noise? (By oscilloscope for example)

klklik, thank you for the reply.

I found the problem. It was not a Pixhawk related problem but an interference between the battery packs and the sensor. Solved by using longer pipes and moving the pressure sensor away from the battery pack while leaving the pitot tube at the same location.


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