ultra lightweight altimeter schematic needed

Hello,
I design a project where an altimeter is needed. The next things must be met:

1. The altimeter has to be ultra lightweight (less than 10grams in total, excluding battery)

2. The altimeter must somehow transmit data (no local storage)


Are you aware of any projects for 1 and 2?

Any thoughts or ideas for 1 and/or 2 are highly appreciated.

An automotive MAP sensor probably would do, for the data.
But they tend to want +5V. So that's two lithium coins plus
a LDO, still probably OK.

When you say transmit, and you want low power, the thing
that probably has to give is the range (or packet rate). Do
you know how fat and how often the data must be sent?

Because I think I've seen bluetooth microcontroller cards,
Arduino or something else, that might come close to the
weight (and be able to take the 0 - 4V pressure signal and
do the arithmetic) but Bluetooth is not for long hauls.

Now, maybe you could do better by something like using
the 0 - 4V signal as a FM modulation input, to an unlicensed
band of convenience, and get more range & minimal weight
in the electronics. Do the processing on the ground, so long
as you can keep calibration (might want to add some sort
of periodic calibration states, use an analog mux to feed
the FM transmitter 0V, 5V, real MAP V, and then you can
get some interpolation endpoints continuously? But then
you have at least a mux and a clock added to the weight.

dick_freebird said:

An automotive MAP sensor probably would do, for the data.
But they tend to want +5V. So that's two lithium coins plus
a LDO, still probably OK.

When you say transmit, and you want low power, the thing
that probably has to give is the range (or packet rate). Do
you know how fat and how often the data must be sent?

Because I think I've seen bluetooth microcontroller cards,
Arduino or something else, that might come close to the
weight (and be able to take the 0 - 4V pressure signal and
do the arithmetic) but Bluetooth is not for long hauls.

Now, maybe you could do better by something like using
the 0 - 4V signal as a FM modulation input, to an unlicensed
band of convenience, and get more range & minimal weight
in the electronics. Do the processing on the ground, so long
as you can keep calibration (might want to add some sort
of periodic calibration states, use an analog mux to feed
the FM transmitter 0V, 5V, real MAP V, and then you can
get some interpolation endpoints continuously? But then
you have at least a mux and a clock added to the weight.

Click to expand...

Thanks very much for the informative answer!
The range bust be something like 10km, maybe more, but just to get an idea. But this has to be covered with no obstacles, direct site.An idea for the transmitter was a class-e 2n7000 amplifier (1-2w) but these operate at higher voltages. may be I could adapt this to 5v operation with reduced output (100-300mW?). Of course this is a solution for the shortwave < 14MHz. Assumming operation at 14MHz a 20m wire antenna is needed, which can be made using very fine enameled coil wire. The data sending does not have to be something special.

A very simple setup I was initially thinking was an analogue pressure sensor connected through an opamp to a varicap of a VXO. The variations of the pressure will cause variations in the voltage and thus a frequency drift. To save battery or to obtain higher voltage, a charge pump can be used and the transmitter could transmit in beacon mode every 30sec or so. the frequency of the beacon will mark the altitude if correctly calibrated. A single pulse would be then what is needed. Maybe I could have two charge pumps charged in parallel and discharged in series to double the voltage, who knows... I cannot think of any simpler setup than this.
Maybe you have any other ideas?
In that case, I would appreciate if you could provide some analogue pressure sensor types to look for.