Anybody know of a circuit to measure wind chill? I'm guessing the best/simplest/cheapest way would be to measure how much current it takes to keep a resister at certain temperature while exposed to Ma Nature's little tantrums but I really don't feel like getting into a theoritical design/prototype/troubleshoot/revise/build/yadda yadda yadda project on this. Something I could get built & calibrated before next summer would be nice- by next week would be fantastic :).
Thanks,
Howard.
A temperature sensor and anemometer connected to a suitable MCU should do what you want. You could use a lookup table based on this:
Leon
IMO, machines don not feel windchill. It appears to be connected to evaporating moisture from a surface. As close a machine could come would be measuring temperature, wind and moisture content of the air.
Rene
-- Ing.Buero R.Tschaggelar - http://www.ibrtses.com & commercial newsgroups - http://www.talkto.net
Wind chill cannot be measured directly, the assumptions of core body temperature and heat diffusion through facial tissue are statistical and it would make no sense to simulate this with analog electronics when it can be computed, also, it appears that the extrapolation of wind speed measurement at a standard height of 10m to a 1.5m average by multiplication by ~2/3 assumes an orographical surface roughness factor of ~0.1m, which again is another statistical artifice. The purpose of wind chill estimation is to obtain a probabilistic risk assessment of frostbite and is therefore not really a physical measurement in the ordinary sense. Why don't you just buy a weather station and use a chart or something.
Yes, but a heated resistor will loose heat faster in moving air compared to still air. In fact it is quite common to measure wind speed by measuring the rate of heat loss from a heated coil or thermistor (hotwire anemometer).
It seems reasonable, to me, that measuring the heat loss from a heated resistor could enable you to calculate windchill in the way the OP suggested.
Temperature and wind speed yes, but surprisingly, humidity has very little effect on windchill. See:
Gareth.
-- ----------------------------------------------------------------------- To reply to me directly: Replace privacy.net with: totalise DOT co DOT uk and replace me with gareth.harris
opinion
Because this is Usenet.
Wind chill is very close to being a bogus idea. To the extent that it is meaningful, it is meant to assess how much faster a person will cool down in a moving stream of air than in a still stream of air of the same temperature. So it is mostly about heat transfer under convection conditions.
I think you are right that what the OP should do is focus on measuring air speed and temperature, and possibly humidity. The wind chill could then be looked up or calculated or whatever. I don't know exactly how they calculate it.
--Mac
If you don't know anything about it, then why are you posting an opinion about what the OP should do?
HAAHAH
Twc=33 + (T-33)(.474+.454sqrt(S)-0.0445 S) {siple (1945) } T=ambient temp Celsius S=Windspeed m/s Holler if you need a version of this rendered down to 8051 assembler (needs a 16 bit math package) M
There is a difference between "not knowing anything about" wind chill (your words) and not knowing "exactly how to calculate it," my words.
You sure are a surly one. ;-)
--Mac
You misspelled "Shirley" ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Eh? Never been in Detroit this time of year have you ?:-)
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |
I always seem to have business back east at the worst-weather times of the year... Pittsburgh on Wednesday :-(
It's cold here today... a cold front with rain came thru yesterday afternoon... it's only +60°F, +15.5°C, here ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Yech :-( The only grass I have here is for the dogs, and the gardener does the scooping ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
You'll need to insulate matching typical clothing and/or skin thermal resistance.
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |
The US and Canada switched to a new formula for calculating wind chill in the fall of 2001. The difference between dry bulb temperature and wind chill temperature is not as great with the new formula.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
I think that fried-egg-on-the-sidewak thing is an urban legend. It takes a closed black car to get into the 160°F air-temperature range, and I've heard numbers of around 140-150°F on good black asphalt... not quite frying temperature... the demos I've seen on TV news show whites looking like congealed snot, yech ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
I took the dog for a walk at night a week or two ago- the wind was ~20-30mph and temperature -22°C (-8°F). Taking a glove off to use my Maglite and bag the leavings, I wasn't across an open field diagonally before all the feeling was out of my little finger in that hand. Wind chill is real enough!
A few miles in that sort of environment without proper clothing and you could be dead. It's not nearly as bad without the wind.
A comfortable -1°C (30°F) and sunny today.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
And it has to be a naked person. It was developed by the military to act as a baseline for cold-weather gear. Anyone wearing clothes will find that a 10 degree wind chill is much warmer than a real
10 degrees.So why is it so popular? It makes the weather report on your local TV station more exciting. A REAL correction factor that tells you how cold it will seem while you are wearing a good coat would be far more useful, but instead they give the bogus numbers.
Trivia: Inb the military tests, females complained about the cold sooner but could tolerate a colder environment without having it disable them.
(This spot reserved for Rich Grise so he can insert a joke about frigid naked females...) :o
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