• Weather conditions or Camera views at WA7X central
• Look at the KI7DX 6 Meter Repeater Web Page
• If you have heard the WA7X beacon, go here
• Go back to The main WA7X "cabin cam" page

The weather station at the cabin consists of a number of sensors being polled by a computer.  These sensors include:

• Temperature sensors.  There are several temperature sensors scattered around the cabin - in and out of doors.
• Wind speed and direction.
• Humidity
• Barometric Pressure

All of these sensors are connected via a "1 Wire Network" (trademark of Dallas Semiconductor.)  The weather data is polled via the serial port on the computer (with a converter) and the data from each of these sensors is read, organized, and presented by the Weather Station software.

The basic "1 wire weather station" was originally created by the folks at Dallas Semiconductor as a promotional product:  A clever way to demonstrate the flexibility of various electronic devices that needed only 1 wire (plus ground) to communicate.  Because each of these devices has its own unique serial number (that no other device ever made - or will be made - has) it can be identified on a network of these devices.  When the program is set up, the calibration of the device "tells" the computer where each device is located - and in that way one can keep track of things.

This original weather station only had the capability of determining temperature, wind direction, and wind speed, but in the recent years more sensors have been developed that allow humidity, barometric pressure, rainfall, and even lightning to be detected and measured.

Dallas Semiconductor no longer makes the weather station, but it is still available from AAG Electronica - plus a number of the accessories mentioned above.  The software used at WA7X was written by Arne Henriksen and is available for either free, or for a nominal fee (depending on which hardware you have, and what sensors you need to have supported.)  The current version (the one that you pay for) is significantly more stable and full-featured than the earlier (free) version and is well worth the money.

A few details about the weather station

The weather station is frequently being upgraded and modified and new sensors being added.  Here are a few points of interest:

• The "Anemometer Temperature" sensor is located in the wind speed/direction indicator.  In the original hardware (that made by Dallas Semiconductor) even on bright, sunny days, the temperature reported was elevated by only a degree or two at most due to heating by the sun.  The current outdoor sensor (the one made by AAG Electronica) is mechanically superior (that is, the bugs have been worked out and it provides better weather protection to the electronics) but although it appears to be the same color, it seems to absorb a bit more infrared than the old one and thus the reported temperature on a bright, sunny day may be 4-5 degrees higher than actual.  Because this sensor is in the wind direction/speed indicator, it is also fairly high off the ground and in the clear.  (Note:  As of 12/20/03, this was renamed from "Outside Temperature" to "Anemometer Temperature.")
• The "Outdoor Temperature" temperature is not affected by solar radiation as it is under an eve on the cabin.  It is, however, somewhat "buffered" by the building's surroundings and tends not to respond quite as quickly to temperature swings.  This sensor is actually insulated from the building by foam insulation - which reduces this effect considerably - but it is still slightly affected.  In other words:  During a sunny day, this sensor's reported temperature may be more accurate, while at other times the "Anemometer Temperature" reading will respond more quickly.  Being mounted against the building, this sensor is not as far off the ground as the "Anemometer Temperature" sensor in the wind instrument and thus it's temperature may also be affected because of that.  (Note:  As of 12/20/03, this was renamed from "Humidity Temperature Sensor" to "Outdoor Temperature.")
• The humidity sensor (as mentioned above) is based on a good quality Honeywell electronic humidity sensor.  This sensor seems to do a very good job in reporting the relative humidity over an extremely wide temperature range.  To improve accuracy, this sensor also has a built-in thermometer that is used by the program to correct for the known effects of temperature on the humidity calibration.  Knowing both humidity and temperature allows one to calculate the Dew Point - that is, the temperature at which the current air mass can no longer retain its moisture without letting go of it.  In other words, if the dew point is equal to the temperature, chances are that it's foggy!
• The barometer is actually located inside - in the water room.  Being a sensitive instrument, it was located in a room in the basement that has a constant temperature.  Being inside the house doesn't affect the barometric pressure reading, however.  The barometer also has its own built-in thermometer and that is used to report the temperature of the water room.  At the moment, this temperature is slightly elevated due to its proximity to other electronic devices (by 2 degrees or so) but one of these days we'll sort that out.  The barometric pressure is believed to be accurate, but that hasn't been officially verified.  It will indicate trending properly, though.
• There are a few other temperature sensors scattered around - and maybe more will be added...
• Note:  As of January 3, 2004, the "glitching" in the Barometric Pressure data seems to be fixed!

Aside from a few of the obvious things, the weather station can tell you a bit more details of present and past weather than might first appear:

• The humidity is a very good judge of what the weather is/has been doing.  If it shows over 95%, it was probably raining or snowing at that time - or in the clouds/fog.
• In looking at the dew point, if it equals the current temperature, the cabin was in clouds (or fog) at that time.
• A sudden drop of barometric pressure (not to be confused by the "glitches") is usually accompanied by wind - and a storm.
• Occasionally, after a heavy snow, the wind speed/direction will get "stuck".  This is indicated by the graph showing zero wind and an absolutely constant wind direction (a straight line.)  On the other hand, there are occasional periods when there is no detectable wind at all - but this is pretty rare.  In other words, if you see no apparent wind speed/direction but there is a lot of new snow, the sensor's probably stuck.  The "stuck sensor" will usually resolve itself after a few hours - when the snow either gets too heavy and falls off, or the wind picks up and blows it off the sensors.

What about other weather station hardware/software?

Other than having a Davis Weather station at home, I don't have much experience with other hardware.  As for software, Arne's software seems to be good enough and flexible enough that there has been no need to change/update it.

Last page update:  20040107

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