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Precision Digital Altimeter

Precision Digital Altimeter

Build with Analog to digital converter NSC ADC12130, a Microchip PIC16F84 controller, a quad op-amp NSC LMC660, a Maxim MAX232 RS232 level shifter, and the Motorola MPXS4100A absolute pressure sensor.
The current concept incorporates a wireless transmitter and receiver and is thought to be used for remote controlled airplanes or appliances with two seperate parts. In other words, we have one dedicated transmitter (acquisition, filtering) and one dedicated receiver part (user-interface, look-up table, calibration, storage), capable of being connected together with any physical layer, e.g. wired, wireless, infrared. If you want to build a standalone altimeter/variometer just for hiking or mountaineering, this setup can obviously be simplified by omitting the wireless components.

So far, only the transmitter part with all its analog circuitry has been completed entirely – the digital receiver part has still to be done, but does not necessarily have to be a PIC microcontroller. For instance, it could also be a personal computer, connected through the standardized RS232 protocol and a wired/wireless interface to the transmitter part.


The (pending) challenge of the receiver implementation is the field evaluation of the most suitable and accurate temperature and non-linear pressure-altitude correction algorithms. There is maybe need for adding a temperature sensor to the transmitter part.

Future Steps:

Field measurements and evaluation of the most suitable temperature and non-linear pressure-altitude correction algorithms, maybe with portable computer to be ready for quick alterations.
Design of the microcontroller-based receiver circuit.
Put all code together and create user-interface and calibration menu with liquid crystal display.
If applicable, a 24C65 EEPROM interface for storage.
If having not enough challenges, real time clock interface to Dallas DS1302.

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