A detailed tour of the KI5OMM weather station.

The KI5OMM weather station is comprised of a blend of both new and old technology.

KI5OMM weather Station

The weather station at KI5OMM was constructed using weather sensors from Davis Instruments. Davis has been a leader in weather station technology for many years and their equipment is both durable and very accurate. Along side the Davis sensors are some backup measurement tools such as lab grade mercury glass thermometers. The thermometers are four basic types – wet bulb, dry bulb, maximum, and minimum. All of this equipment is housed in an instrument shelter known as a Cotton Region Shelter that provides a stable environment for temperature, dew point, and humidity measurements.


Inside the instrument shelter are various sensors and the glass thermometers. Temperature readings should always be taken in the shade away from the direct UV rays. The Cotton Region Shelter design allows for free airflow inside the shelter while shielding the sensitive thermometers from the direct sun. This shelter design has been the standard for the National Weather Service for many years. It is a derivative of the original Stevenson Screen shelter design originating in the UK from the 1800’s. The development of newer electronic temperature sensors has led to miniature versions incorporated around the sensor and are more widespread in use today. Nevertheless, Cotton Region Shelters are still being used all over the USA due to the fact that the simple design is effective. I built my version of the Cotton Region Shelter using louvered closet doors that were sawed into sections and glued and screwed into a box with two opening doors on the front to access the instruments inside.


This view inside the shelter shows the Davis temperature and humidity sensor at the top right. This sensor is 5 feet above ground level as per the NWS guidelines. At the left are the wet bulb and dry bulb glass mercury thermometers. The small jar is filled with distilled water and a cotton wick draws water up to the bulb of the wet bulb thermometer. The natural evaporation of the water in the wick around the bulb creates a radiational cooling effect which in turn cools the thermometer bulb slightly. As the humidity changes throughout the day, the wicking effect changes accordingly. To the right of the wet bulb thermometer is a standard dry bulb thermometer. When taking manual readings with these two thermometers, you note the difference in degrees between the two, and using a special chart you can then get a very accurate reading of the humidity and air temperature. These instruments are used for backup and calibration purposes only as the Davis electronic sensor is what is actually recorded and plots on the KI5OMM website.


On the side of the shelter is the Davis ISS transmitter. Originally Davis had this board enclosed in a self-contained box that also housed the rain gauge and other instruments. Since I was adding an external yagi antenna and separating the various sensors to meet my layout needs, I removed the board from the original housing and mounted it inside a larger waterproof electronics box. Inside is the incoming 12VDC power cable and a power converter to bring the voltage down to 4.2VDC to supply the ISS board. I used bronze wool stuffed around the cable openings to keep crawling insects out of the box when the door is closed.


On the KI5OMM website you can view a weather webcam that is set up for time-lapse photography. I use a Boavision IP camera that is programmed to take a single image every 5 minutes. These images are compiled into a short time-lapse script that is shown on the website. Folks enjoy seeing an actual view of the skies and weather conditions along with the standard weather station information. They say a picture is worth a thousand words..





The Davis console back inside the building receives the signals sent from the weather station outside. This is the heart of the weather station as it reads raw weather data and compiles it into an understandable format. Eventually, it stores it’s information onto a built-in data logger for storage. Since my weather station is located in a remote area of my ranch, the standard antennas on the console and the ISS unit were not able to read each other. A solution was found by using two yagi antennas pointed directly at each other. This necessitated removing the old standard antennas off of each unit and splicing in a coax cable to run outside to the new external antenna. Since I am a radio operator (KI5OMM) and I have a good understanding of antenna theory and design, my solution works well. I usually get a 95% reception signal with the two units located 1/2 mile apart from each other.


The computer that I use to display the weather data on the website is a standard Raspberry Pi 3b. This is a tiny one-board computer that quietly runs 24/7 uploading data to the KI5OMM website every 5 minutes. It is dead silent and sips very small amounts of power. I use a Linux operating system to run WeeWx weather data software. Additionally I also use the Belchertown skin by Pat O’Brein.




The weather station is about as accurate as possible and the data is presented in a useful and timely format. As it compiles and stores data, the climatological record will continue to improve in accuracy.

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