Primary mission
Like every other team, we have a primary mission that consists of measuring the air pressure and temerature, and transmitting it via radio to the ground as well as storing it on an SD card. And after the flight, we will generate temperature, altitude and pressure graphs! We might also create some other graphs related to our secondary mission.
We decided to use thermistors for temperature measurements. Although thermistors are tricky to use due to their non-linear response, they have much better performances than other sensors: they are reactive, have a small margin of error, a small size and a low cost. Compared to thermocouples, thermistors are more sensitive and work well over a wide temperature range. We performed extensive tests with a large panel of thermistors to select the most adequate ones for our mission.
We tested a number of thermistors for thermal inertia (which must be very low to ensure an adequate response time), stability and accuracy. The two thermistors we selected to include in our can should provide measurement with a respective accuracy of 1.2 and 0.6°C.
Pressure measurements are performed using Adafruit’s BMP388 sensor, and altitude is also derived from the pressure data, using the sea-level pressure. Our test confirmed the very good response time and accuracy of this sensor.
For the communication, we use XBee modules which provide great and reliable performance. Our RF link is operating at 2.4Ghz (an authorized frequency for model competitions), and our tests demonstrated a reliable transmission in semi-duplex mode up to 1000m.