pine cone

I'd think it may compare quite well, you'd have to link it up to some sort of pointer via a linkage of some sort...If you then calibrated it against a decent instrument it may well keep a reliable performance. I suggest you do the experiment and let us know how you get on.

Del

Not to be horribly stodgy on this, but, huh? How in the world would you calibrate a pine cone? And what is a pine cone's accuracy and repeatability? If this is purely experimental you should check it against a calibrated instrument and report it as to ASTM D4230, or the appropriate NIST or ISO standard.

Don't be a paper hat, read my post c-a-r-e-f-u-l-l-y it tells you exactly how to clibrate it.
Draw a scale (say every millimetre) and the number it with reference to a known instrument. (or generate 100% relative humity with a kettle or some such)
Once you have calibrated it... you can then take readings every day, hour or whatever and see how repeatable etc it is...Jeez...it's not my question...

Slaps furry head with paw...

Maybe get your faimly pet to help you especially if you have to use scissors..

(Just teasing...pls don't take offense)

Del

observer not to scale?

Ha! Del, If you need venture capital to start producing these, let me know. We can sell these in roadside "cracker barrel" restaurants here in the states. Instead of all those lines, and the pointer thingy, and all that calibrayshun stuff, we'll just print the following instructions on the scale:

If the pinecone is wet, its 100% humidity.

If the pinecone is covered in snow, its winter.

If the pinecone is dry, Its a nice day.

Caution, Do not place pinecone hygrometer under roof or inaccurate readings may result.

Me-OWW!

milo

Del, you're hilarious and quite possibly over medicated, but I think you are missing that hygrometers are not linear. Instead since they run from 0-100% they can only be exponential with the extreme upper and lower limits being basically useless. If the pine cone isn't standardized (ha ha) the hygrometer will be pretty limited. Kinda like a Galileo thermometer, cool but useless.

I do dig the "non-biased observer" on your drawing.

ha no, I don't miss much...although conversely I don't hit everything...
I was assuming the scale would be marked up over a period of time to correspond to the reference...covering dry and wet days until most of the scale was covered. Then you could start checking how it drifted with time, tomperature, phases of the moon, the nasdaq index or annything alse you fancied...heck you could even try it as an earthquake prognosticator.

I once had a stretch belt that I once wore when I rode home on my motorcycle in the rain. It got about 3 inches longer when wet. I thought it would make a good medium for a humidistat. I also had a wooden bird that would keep bending over as long as there was water in a Little cup that he would dip his beak into. The speed of his dipping was probably related to the relative humidity (his beak soaked up water). One of those and a temperature cricket and you would be all set.

Hello Guest,

Is the Pine Cone:

1. Removed from the tree?

• Green
• Open, shedding seeds
• Dry and decrepit
  

1. Attached to the tree?

• Green
• Open, shedding seeds
• Dry and decrepit

Please advise further, with as loose Specifications can often be costly to the Specifier and/or Client.

Kind Regards....

In December last year a woman were looking for pine cones to paint and used for decorations.

As usual I overdid it and brought here a box full. She only used a few and I had to sneak them in the garbage disposal bin (a few at a time). Only last week I disposed the last batch.

And now after all the trouble I realize I was scrapping state of the art scientific devices.

Sparkstation - I had a whole range of models (young, old, dry, green etc etc) and you are right they all will give different results and even differ as time goes by.

I would say you would require at least 11 and calculate the weighed average.

The pine-cone-hygrometer reaction would be so slow as to render it completely out of the running.

Ok, humor aside, professional weather stations and instruments don't have a direct system for measuring the humidity. The humidity is calculated by taking the temperature of the air with two identical temperature measuring devices, one with a normal configuration ant the other with a piece of water soaked material that covers the temperature sensor. This then gives you what is referred to as the wet and dry bulb temperatures which are then used to calculate the relative humidity.

Relative humidity is actually a pretty useless measurement because it can't be applied to anything of major importance. What is important is what is revered to as the dew point which is closely related to the wet bulb temperature described earlier. The dew point is the temperature a given parcel of air that is being cooled will become saturated and therefore any further cooling will result in water condensing and forming either a film of water (in other words dew) over surfaces or droplets of water suspended in the air (in other words clouds or fog).

The dew point is used extensively in meteorology for calculating things like the altitude of the base and thickness of clouds. For example if the ground temperature was 30° C and dew point 12° C then if clouds start to form the base will be 6,000 feet above the point the measurements were taken.

Ok, so how do we go from a temperature of 30° C and dew point of 12° C to a cloud base of 6,000 feet? Well it's really quiet simple. If a parcel of air is somehow lifted up by a hot spot on the ground or a mountain that deflects the wind upwards the temperature will drop by 3° C for every 1,000 feet the parcel of air rises. In this case if the air were to rise by 6,000 feet then the temperature would have dropped by 18° C to 12° C which is the dew point. If the air were then to rise further then the temperature would drop further and the water that was dissolved in the air will condense out forming a cloud.

Calculating the thickness of the clouds is somewhat more complex as you need to take into account the actual temperature profile of the atmosphere at that time and the latent heat of vaporization. When the energy that was consumed changing the state of the water for liquid to gas is released when it condenses it heats the air. As a result air that is inside a cloud or below dew point will only cool by around 1.5° C for every 1,000 feet height gain. As a result if there is dry stable air present and a good supply of warm moist air the cloud will just jeep building until it reaches the tropopause where the atmospheric temperature starts increasing with altitude. This is how the classic cumulonimbus clouds with the anvil shaped tops that are associated with thunder storms form. The flat anvil shaped top is where the rising air has hit the tropopause and stopped rising.

If the supply of warm moist air is sufficient, like over shallow tropical oceanic regions, then the clouds will just continue to grow in size sucking in more and more warm moist air and energy till they start rotating due to the coriolis effect and form a tropical cyclone (hurricane in the North Atlantic or Typhoon in the Northern Pacific and Indian oceans).

Direct measurement of humidity is highly inaccurate as the sensitivity of the media to water vapor is easily offset by temperature, contamination, atmospheric pressure and a whole host of other things. If you wish to calculate the humidity with any degree of accuracy then the best way is to use two thermometers and a psychometric chart, table of calculation.

PS There are systems in automated weather stations that do it with some nifty electronics and a host of parameters but any one that is worth using is going to have a fairly hefty price tag. Wherever there is easy access the dual thermometer system is the most common method and definitely the way I would do it.

Hi masu,

The two thermometers (sling hygrometer and equivalent) are not very convenient, and the chart has to be corrected for altitude. There are digital readouts available at several price ranges. I once saw a unique unit that used a gold mirror that was cooled until dew condensed onto it, interrupting a reflected light beam (a dew point hygrometer).

S

G'day StandardsGuy,

There are a host of methods including units that use, blond hair, teflon films, condensation membranes (like the one you described) resistive reactants and so on.

The trouble with them that you are lucky to keep them calibrated to much less than ±10% which is completely useless for weather forecasting. The wet and dry bulb is definitely fiddly and needs to be corrected for the altitude and barometric pressure but with modern electronics can easily be allowed for by sticking a microprocessor into the loop.

Reengages are another bugger of an instrument but there are some really good ones that require little to no maintenance. They work by using a series of extremely sensitive accelerometers that ate attached to a suspended metal sheet of known area and mass. By measuring the acceleration that is caused by the drops impacting the metal sheet you can calculate the amount of rain or hail.

They don't work too well with snow and dew but you can utilize other systems to measure those fairly accurately and reliably.

Weather forecasting accuracy is dependent on the accuracy and diversity of the parameters you can measure and a lot of people don't understand how difficult it can be to measure many of the parameters like dew point to a useful accuracy. Most people would say an error of ±10% measuring the humidity was fine but it could easily be the difference between a few cumulus clouds a couple of hundred feet thick and a full blown cumulonimbus storm cell that can be up to 60,000 feet thick.

I have always been interested in the weather and when I was studying for my pilots license found the meteorology totally fascinating. When I started flying gliders I did a lot more research on the subject and have written a couple of programs that were used to predict thermal activity. The only hassle was that the results were highly dependent on the accuracy of the reading fed into them and the currency of the atmospheric sounding. When the information was good the results were usually accurate time wise to about 15 minutes, altitude wise a few hundred feet and strength wise about 10%. I havn't used them for about ten years and the amount and accessibility of meteorological conditions has improved dramatically since then. I should dig them out and see how they can be updated to use the huge increase in information that the WWW now offers.