[time-nuts] Room temperature control (was: Holdover, RTC for Pi as NTP GPS source)
jn6wfo at gmail.com
Wed Nov 1 15:16:22 EDT 2017
I remember visiting the metrology lab in HP Palo Alto (Glen Whatshisname)
when I worked for them in the early 70s. There was a set of toggle switches
on the wall; for every person inside, one switch was turned on. I don't
know how well it worked but apparently, well enough for 1970s-vintage
On Wed, Nov 1, 2017 at 11:08 AM Attila Kinali <attila at kinali.ch> wrote:
> On Wed, 1 Nov 2017 15:37:38 +0100
> Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
> > Silly people
> > want a relative comfortable temperature and well, building A/C is
> > typically bang/bang regulated so you get what you paid for.
> My short stint in the HVAC business taught me, that it's surprisingly
> difficult to stabilize room temperature to better than 2-5°C.
> It starts at such simple things as measuring the temperature.
> The position of the sensor and its distance to the wall make a huge
> difference. Just 1cm further away from the wall, or 10cm up or down and
> you get 2-3°C difference. An A/C system usually controls the temperature
> of the air inlet, which is the simplest thing to do, but actually you want
> to control the (heat) power flow into the room. And this is something that
> has not been possible with standard equipment until recently.
> The best we can do today is to have a well insulated room (no windows
> with whith unknown power flows) and measure the temperature at a few
> strategically choosen points. Then control the heat influx and
> outflux using an approriate control loop. This will still result
> in deviations of 1-2°C when somone walks in.
> Attila Kinali
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> use without that foundation.
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