[time-nuts] Re: Long term stable environmental sensors

[Poul-Henning Kamp]

> So, now I'm about to design and build a new system that has better long
> terms stability.

PT100 or PT1K are fine and stable for temperature.

We have no technology which can make long term stable precision
measurements of humidity and pressure:  You will need periodic
calibration no matter what kit you get.

"Long" calibration periods are two years, and if you can avoid
condensation, you can get down to 0.5%RH drift over that period.

The big player in this space is Vaisala.com and they are not cheap.

Calibrating RH and pressure sensors are essentially just highschool
physics experiments, and if that's your hobby: Go for it.

You dont need to do it /all/ from scratch, see for instance:

	https://store.vaisala.com/en/products/HMK15

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.