Temp/Humidity control systems?
Use one of the Wine cellar room coolers -- they keep the temperature and
humidity fairly constant. Typically ~55F but can vary it. Breezaire and
others are vendors in this area. The units look like a window
airconditioner.
This will work to keep the temperature in a given range, but with rather
abrupt on/off cycles.
If you want a steady temperature, it seems like you need a lot of thermal
mass and insulation.
On Wed, Oct 26, 2016 at 11:59 AM, John Ackermann N8UR jra@febo.com wrote:
I may have the opportunity to build a small "clock room" and am
considering whether I could make it an environmentally controlled space.
I'd like to learn about the options for doing this.
The space would probably be 6x8 feet or so, in a basement with one outside
wall.
Can anyone point me to purveyors of the hardware to do something like
this? Because I'll have a limited time to build this, I'm looking for
something that uses more-or-less off the shelf gear, and not a whole lot of
custom engineering.
Thanks!
John
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/m
ailman/listinfo/time-nuts
and follow the instructions there.
On 10/27/2016 03:41 AM, Poul-Henning Kamp wrote:
Over insulating is a 100% sure-fire way to get unstable temperature inside,
because it amplifies the consequences of any change in power dissipation.
It is a classic mistake to build a 100mm insulated enclosure inside an
office-like environment and end up having less stable temperature on
the inside than the outside.
Cinder blocks is a much better material for that scenario, because they
have both thermal mass and inertia (= heat capacity and heat impedance)
True Poul-Henning Kamp.
My application was to ecologically stabilize a room exposed to
outside weather. I am pleased to see the heater rarely come on,
even on cold Winter days. I attribute that to the insulation
and equipment mass (half-century old computer, avionics, and
amateur radio equipment). Even in the Summer heat, the room
stays cooler than air temperature (barn roof and day/night
averaging?).
John's Georgia basement may also enjoy natural cooling and
thermal inertia. Cinder blocks may be optimal. We really need
to know John's goal and existing conditions.
Mike - AA8K
I'm not sure I follow the insulation is bad argument, thermal time constant
= RC, better insulation, longer time constant.
On Thu, Oct 27, 2016 at 12:37 PM, Mike Naruta AA8K aa8k@comcast.net wrote:
On 10/27/2016 03:41 AM, Poul-Henning Kamp wrote:
Over insulating is a 100% sure-fire way to get unstable temperature
inside,
because it amplifies the consequences of any change in power dissipation.
It is a classic mistake to build a 100mm insulated enclosure inside an
office-like environment and end up having less stable temperature on
the inside than the outside.
Cinder blocks is a much better material for that scenario, because they
have both thermal mass and inertia (= heat capacity and heat impedance)
True Poul-Henning Kamp.
My application was to ecologically stabilize a room exposed to outside
weather. I am pleased to see the heater rarely come on, even on cold
Winter days. I attribute that to the insulation and equipment mass
(half-century old computer, avionics, and amateur radio equipment). Even
in the Summer heat, the room stays cooler than air temperature (barn roof
and day/night averaging?).
John's Georgia basement may also enjoy natural cooling and thermal
inertia. Cinder blocks may be optimal. We really need to know John's goal
and existing conditions.
Mike - AA8K
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/m
ailman/listinfo/time-nuts
and follow the instructions there.
There is a wax which melts at 70F. Phase change stores and releases a lot of heat.
Somewhat optimistic IMHO
https://www.wired.com/2015/05/table-sucks-heat-lower-ac-bills/
http://www.stacoolvest.com/news/
Technical:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4809117/
On 10/27/16 8:02 AM, John Hawkinson wrote:
jimlux jimlux@earthlink.net wrote on Thu, 27 Oct 2016
at 07:51:37 -0700 in e46613e9-19c7-09dd-e006-83dce73419eb@earthlink.net:
(and frankly, if someone made something that opened/closed my
windows, I'd love that too, for the same reason.
No, the existing windows - we need to be able to see out of it.. We
have the usual aluminum frame sliding windows.
On 10/27/16 8:06 AM, Poul-Henning Kamp wrote:
In message 837330DB-2015-4AE5-8C9C-F444F569FC1B@n1k.org, Bob Camp writes:
Your “time cave” does not have a specific spec on temperature or on humidity.
You get to pick a number for either one. Anything in the “non condensing” (let’s
call it < 80%) range for humidity is likely ok. Temperature up to 40C is probably
ok for any gear that I can think of. As long as you never go in and out of the
cave, comfort in the cave is a non-issue.
Danger Will Robinson!
Under no circumstances should your dewpoint be above the temperature on
the other side of the door.
If you have 40C at 80% humidity your dew-point temperature is 35C, which means
that whenever you open the door your clock cave will fog up.
If you run your clock cave at 40C, humidity needs to be well below
30% to hold the dewpoint below room tempreatyre. That is both hard,
expensive and prone to electrostatic discharges.
Assuming the humidity in the basement is under control (if not, fix that), all I need
to do for humidity in the closet is to exchange air with the basement.
"fix that" is usually non-trivial, and from very to horribly expensive.
The cardinal rule is that you should only exchange air (basement/outside,
or cave/basement) when the air outside has lower ABSOLUTE humidity.
And I keep stressing that it is ABSOLUTE humidity, because people simply
don't pay it enough attention.
25C/40%RH air holds 9.2 g/m³ water ... as does 15C/72%RH air.
This is why a lot of people in costal climates who ventilate their
basement during summer "to dry out the basement" get the exact
opposite result: The air outside is a lot wetter than on the inside.
One would think that somebody had designed fans to measure this,
but it is expensive: Cheap humidity sensors measure relative humidity
and you need to correct for both temperature and pressure to get
absolute humidity.
And having looked into this in some detail - there's a whole lot of "go
look at a psychometric chart" when you try and write some code to do the
conversion.
It's similar to the "steam tables" (in fact, it's identical to the
problem of generating steam tables, it's all about vapor pressure of
water vs temperature and such)
There's not some nice equation to solve - It's more done by an iterative
solution of the equation that goes the other way.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4813973/pdf/sensors-16-00398.pdf
has some of the background
And therefore, at the risk of repeating myself again:
If you build your clock cave in the basement, it should be air-tight
and you should manage the humidity in it separately from the rest
of the basement.
PS: Here is a good webcalculator:
http://go.vaisala.com/humiditycalculator/5.0/
NIST-traceable hygrometers are readily available in the $200-$400 range.
Or you can get a couple of airtight boxes of precisely the same volume and
go gravimetric.......................
On Thu, Oct 27, 2016 at 9:43 AM, Ron Bean time@rbean.users.panix.com
wrote:
- You cannot "feel" absolute humidity, always measure it.
And since this is time-nuts: Measuring humidity accurately is tricky.
According to people who have tested them, commercial electronic humidity
sensors, when tested in a lab, have never come anywhere close to the
accuracy claimed in the data sheet. The best you can hope for is
consistent readings, not absolute accuracy.
The exception is the "cold mirror" type of sensor, which measures the
dewpoint by cooling a mirror and bouncing a light off it to sense the
temperature where dew condenses on it. Those are expensive, and they
require maintenance to keep the mirror clean.
BTW some of us are more sensitive to humidity than others. I can't tell
you the RH of a room, but I can tell you when it's too dry for comfort.
I want it as close to 50% as I can get it without growing mold on the
walls. Some "experts" claim that 30% is good enough for anyone, but
they're wrong.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
--
Intelligence has never been proof against stupidity.
Just for the fun of it, here is how NIST measures humidity.
https://www.nist.gov/sites/default/files/documents/calibrations/sp250-83.pdf
On Thu, Oct 27, 2016 at 3:30 PM, William H. Fite omniryx@gmail.com wrote:
NIST-traceable hygrometers are readily available in the $200-$400 range.
Or you can get a couple of airtight boxes of precisely the same volume and
go gravimetric.......................
On Thu, Oct 27, 2016 at 9:43 AM, Ron Bean time@rbean.users.panix.com
wrote:
- You cannot "feel" absolute humidity, always measure it.
And since this is time-nuts: Measuring humidity accurately is tricky.
According to people who have tested them, commercial electronic humidity
sensors, when tested in a lab, have never come anywhere close to the
accuracy claimed in the data sheet. The best you can hope for is
consistent readings, not absolute accuracy.
The exception is the "cold mirror" type of sensor, which measures the
dewpoint by cooling a mirror and bouncing a light off it to sense the
temperature where dew condenses on it. Those are expensive, and they
require maintenance to keep the mirror clean.
BTW some of us are more sensitive to humidity than others. I can't tell
you the RH of a room, but I can tell you when it's too dry for comfort.
I want it as close to 50% as I can get it without growing mold on the
walls. Some "experts" claim that 30% is good enough for anyone, but
they're wrong.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/m
ailman/listinfo/time-nuts
and follow the instructions there.
--
Intelligence has never been proof against stupidity.
--
Intelligence has never been proof against stupidity.
You are correct to question commercial humidity sensors.
It seems to have come about because no-one can make a dollar by selling humidity.
Manufacturers do not tell the truth, they think ours is as good as theirs so we
should claim the same accuracy. People buy these sensors, believe them, and buy more.
It is not hard to measure humidity/temperature. (they should be measured together).
Cover the bulb of an ASTM32C thermometer with cotton gauze. Insert it through the wall
of a short length (18”) of 4” metal tube, insert another ASTM32C thermometer through the side
of the tube 4” upstream. Put a computer fan on the outlet of the tube sucking air over
the thermometer bulbs at about 4m/s. Wet the thermometer bulb, but NEVER touch it with your fingers.
In about 3 minutes you can take two temperature readings. There are a number of tables and calculation methods,
some much worse that others that will convert these values to air temperature, Relative humidity,
Dew Point temperature etc. You get accuracy of 1% from temperatures measured to 0.1C.
If anyone is interested I have basic routines for XCEL spreadsheet use to do the hard work.
This is based on the WMO Reference Psychrometer developed by Russel Wylie of NML Australia.
On 28 Oct 2016, at 12:43 AM, Ron Bean time@rbean.users.panix.com wrote:
- You cannot "feel" absolute humidity, always measure it.
And since this is time-nuts: Measuring humidity accurately is tricky.
According to people who have tested them, commercial electronic humidity
sensors, when tested in a lab, have never come anywhere close to the
accuracy claimed in the data sheet. The best you can hope for is
consistent readings, not absolute accuracy.
The exception is the "cold mirror" type of sensor, which measures the
dewpoint by cooling a mirror and bouncing a light off it to sense the
temperature where dew condenses on it. Those are expensive, and they
require maintenance to keep the mirror clean.
BTW some of us are more sensitive to humidity than others. I can't tell
you the RH of a room, but I can tell you when it's too dry for comfort.
I want it as close to 50% as I can get it without growing mold on the
walls. Some "experts" claim that 30% is good enough for anyone, but
they're wrong.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Ha!
That is the system my brother Greg Scace designed and built while at NIST. He has given a lot of papers around the world on its metrology technology.
On the side, he manufactures the reference calibration tools for espresso machines https://www.espressoparts.com/scace-2-espresso-machine-thermofilter-temperature-pressure-device.
Greg is still working there… as is his wife Casey (on cryptography)… and my father Bob Scace worked there for 25 years on microelectronics and nanotechnology… my other brother Brian retired recently from NIST… and I worked there for a few years 1978-1981 on international data networking problems. I think the Scace family has the record for maximum number of family members employed at NIST.
— Eric Scace
On 2016 Oct 27, at 13:32 , William H. Fite omniryx@gmail.com wrote:
Just for the fun of it, here is how NIST measures humidity.
https://www.nist.gov/sites/default/files/documents/calibrations/sp250-83.pdf