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

[Lux, Jim]

On 11/29/22 9:43 AM, Björn wrote:
> Many 🌙 moons ago I scored a bunch of DPM 7885 pressure sensors off eBay.
>
> The herd of 10ish units were all inside 70cm (pressure converted to altitude by standard atmosphere model).
>
> The local guy calibrating private aircraft altimeters was not interested. The sensors were likely superior to his (transfer) standard.
>
> /Björn
>
> Sent from my Phone


A longer time ago (1980s) I was building SAW based pressure sensors as 
altimeters - they wanted 1 foot accuracy from SL to 40,000 ft.  We had a 
fancy calibration setup that used some form of sensor that used a force 
balance of some sort (there was this motor that moved a bead chain on 
some sort of mechanical device.. I can't remember the details.)

I learned then "do not let Helium near a sensitive absolute pressure sensor"

It turns out this is a problem on ISS - the atmosphere on ISS has a 
remarkably high helium concentration (a few percent IIRC) because it's 
used for packaging, as a propellant, etc.