A key question when designing an altimeter, whether it be for an airliner or kite, is where best to measure the air pressure or, more specifically, the ambient air pressure not disturbed by the passage of the aircraft or the kite. Considerable effort goes into addressing this problem when finding the optimum location for an aircraft’s Static Port, i.e. the place where the pressure is truly ambient and not affected by the roll, pitch, yaw or speed of the craft. See for example the article by Reinhard Metz:
Unfortunately I don’t have access to a wind tunnel and so had to rely in guesswork when locating the static port for this unit. Common sense suggests that the airflow, and therefore the pressure, will be least disturbed if measured well ahead of the moving object (in our case the electronic enclosure). In this design the static port comprises an array of 6 small holes located 50mm ahead of the enclosure on a streamlined tubular probe that projects ahead into the airflow. A collar is fitted inside the probe into which is sealed a 3mm, flexible, PVC tube. This tube feeds the air pressure to the barometric module via a manifold glued over the sensor chip. It is important that this manifold is sealed to the board to ensure that it is the probe’s pressure that is measured, rather than that inside the enclosure (which may not be ambient).
By default the Artemis logger logs a header line, real-time, inertial readings and other parameters not of immediate interest. A terminal program is used to configure the logger to isolate the data stream required, in this case real-time, temperature and pressure at a rate of 5Hz which gives sufficient temporal resolution.
I have written a BASIC program to calibrate, scale and plot data from the SD card as graphs that accompany flight videos on the GALLERY page. My code is included in the ZIP file here.