Table of Contents
Barometer and altimeter ALTIMET01A
A digital barometric pressure sensor for precise measurements of altitude and temperature. Sensor output is digital - either to SPI or I2C. It differs according to the type of fitted sensor.
Module construction
The module is designed to be screwed to the base. The screws can be broken off, so the PCB can be glued directly to a flat surface, decreasing the weight and space requirements. You can see an example of this solution in uav construction.
Possible sensors
The module can be fitted with following sensor types:
Communication with sensors
MLAB documentation contains examples of connections for microcontrolers arm, PIC and AVR.
Furthermore, both types of sensors (with I²C or SPI interface) can be read directly from the computer using a Python library pymlab and conversion modules USBI2C and I2CSPI.
Parameters
When measuring the parameters of MPL3115A2 during the ABL01A project, we found out that the pressure measurements were functional at least up to 16 km (approximately 10kPa), a much better result than the parameter stated in the catalogue list. On the other hand, the internal pressure atmospheric model is only usable up to 10 km of altitude - in higher altitudes it experiences considerable inaccuracies.
Module testing
The realisation of a testing system for MPL3115A2 sensor uses I2CHUB02A module, that enables a testing of more sensors at once. Sensors are placed together in a vacuum bell with controlled pressure and the pressure measurements are (together with temperature measurements) read by I²C bus. At the same time, a pressure measured by a reference measuring device DPI 145 is read by the main computer.
Reading the pressure via I2C bus, a following python code was used: External link
Modul power supply
I2C module version has to be supplied by a stabilised voltage smaller than 3.6 V, otherwise it can be destroyed.