barometric pressure sensor on ground station

iskess June 5, 2014 at 7:37pm

My guess is that it is like a greenhouse in that hollow wing and it gets hot in the sun.
Test it by leaving it in the shade vs the sun and see if it changes the drift.

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Dwgsparky > iskess June 6, 2014 at 4:14am

If the wing is sealed the pressure could increase with thee heat. I had the same problem with flying wing, solved it and the pressure difference by passing a plastic drinking straw completely through the wing top to bottom then putting a vent hole in the side of the straw near the sensor. The sensor then sees the average pressure, simple

iskess June 5, 2014 at 7:09pm

Where is it mounted, on top of the wing? There is a significant vacuum created on the top of the wing when creating lift. This will show as a higher altitude. Which was does it drift?
Heat will also show as a higher altitude.

Cody Remington > iskess June 5, 2014 at 7:28pm

Its a hollow molded wing so I installed it inside the wing. It is showing a higher altitude. I will try installing it in the fuse to see if that makes a difference.

iskess June 2, 2014 at 11:33am

That parameter was put in there by Tridge for the Outback challenge. It is not supported by mission planner, Tridge uses his own GCS.
Agreed that your 50ft drift is not from atmospheric changes. I think you'll notice that it always drifts in the same direction? Usually this is caused by heat build up around the sensor, although the sensor is temp compensated. Before flight, let it warm up for five minutes with your GPS, then do a Preflight Calibration (Actions Tab) to reset your baro and speed to zero.

Cody Remington > iskess June 5, 2014 at 9:31am

Yes it does seem to be in the same direction. I have the sensor installed in the wing. However when I leave the plane out for a while and it still drifts.

Pedals2Paddles June 2, 2014 at 7:21am

No, which leads to the inevitable next question... Why would you want/need one on the ground? Are you thinking about a way to tell the flight controller how to compensate for changes in atmospheric pressure while in flight? For example, if changes in the weather result in a drop in pressure while in flight, that change could be conveyed to the flight controller so it adjusts appropriately?

Pedals2Paddles > Pedals2Paddles June 2, 2014 at 8:36am

50ft of altitude drift will not be solved by a ground barometer. Trust me, the atmospheric pressure is not changing that much over the course of every one of your 10-15 mintue flights. Unless you are punching through the eyewall of a hurricane. Atmospheric pressure changes would be taking place very gradually over a long period of time. Not what you are experiencing.

Something else is wrong. Vibration and direct sunlight exposure to the barometer can cause altitude hold problems.
Cody Remington > Pedals2Paddles June 2, 2014 at 7:28am

Yes, It looks like the GND_ALT_OFFSET parameter is in there for this function. I seems to constantly be getting 50 feet of drift on each flight.

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barometric pressure sensor on ground station

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