Altimeter

Hi
I want a high resolution Altimeter(1 cm resolution ) and i find this

and this

These are expensive but I want resolution 1 cm and these are the only sensor which i find . Please write your opinion thanks

With lots and lots of averaging (over many minutes), you might be able to get 1 cm resolution with any of the latest MEMS barometric pressure sensors.

However, atmospheric pressure can change quite rapidly, even over a few minutes, and day to day pressure variations can amount to hundreds of meters in change of apparent altitude.

Thanks you my friend
I can initialize the sensor as 0m altitude the first value but the most sensor have 10cm resolution

the most sensor have 10cm resolution

Averaging increases that resolution, as the sqrt(N). Average 100 points with 10 cm resolution to get 1 cm resolution.

If you need 1cm resolution of altitude, you’re measuring the wrong variable or using the wrong method. What are you attempting to do that needs that kind of resolution?

The method works fine, if the local atmospheric pressure is stable (which it usually isn't).

That’s my point. Pressure based altitude is wholly unsuited for any type of absolute accuracy due to the inherent fluctuations.

Radar altimeters are one example of overcoming the limitations of pressure based instruments and trying to achieve 1cm of resolution when most are concerned with hundreds of feet being good enough, strikes me as trying to apply the wrong technology to the problem. As is typical around this forum, most of these question tend to have their origins in the x-y problem

That's my point.

We agree. Now, let's the OP discover this for him/herself.

I have a BMP280 GY barometric sensor (few bucks). The old GMP180 (if you find one) is 1-2 USD. It does the job of accurate measuring the barometric pressure.

That is what a pressure sensor does: measures the pressure :-)).

The barometric pressure is proportional to:
a) altitude
b) whether

Altitude does not change (obviously) but the whether does.

++

My solution: make the barometric sensor to learn. On other words, calibrate it.

So, log the values of the pressure over - say - one month, once a day. Calculate the variation in pressure. (+-).

You get to something like:

(Min value of the pressure - Max value of the pressure) -> for a given altitude.

Repeat the same for an altitude as much different to the first as possible.

Then, you may say that for a certain interval which is equal to the one as above, the altitude decreases or increases by a certain step.

Code this calculus and logically integrate this finding into the values to be displayed.

You may see that the accuracy of the sensor is not relevant in measuring (deduction in fact) the altitude. That is why I said a BMP180 is good enough and does not make you to rob a bank.

"weather"

@Jremington

Thank you!

The noise in these sensors in my experience is at the 10's of cm level, you will not get 1cm accuracy
at all, you might be able to get 1cm resolution if heavily low-pass filtered, but accuracy or repeatability will be
nowhere near that with a MEMS sensor. Temperature drift will be a big factor, which many of these devices will
partially correct for internally, so a stable temperature is likely to increase the pressure performance.

For instance the HP206C datasheets states an accuracy of +/- 1.5 mbar, a span of about 25 metres at sea level.

Brielfly, this is a barometer sensor, not an altimeter.

It can be use to demonstrate how the pressure changes by altitude, but not to actually measure altitude bellow a certain rough accuracy.