Welcome to the North Park University Physics and Engineering Department

Physics and Engineering: The Helwig Station


This weather station is located on the rooftop of Helwig Recreation Center. The station is a Davis Instruments Wireless Vantage Pro2 Plus™ with 24-Hr Fan Aspirated Radiation Shield. The unit transmits data wirelessly to a console and data logger located in the Helwig Center. A virtual GNU/Linux server retrieves the data from the data logger via the Internet using wview, a collection of open-source (GPL) programs that interface with the data logger and generate the HTML pages.

The Vantage Pro2 is a high quality consumer/hobbyist-grade weather station. For a reasonable price, you get a solid station that while not research-grade is still accurate for most everyday purposes.

All photographs below are of the first weather station, which was decommissioned 14 June 2012. The replacement weather station looks nearly identical. Data from the station is displayed here.

Close-Up Photos of the Sensor Unit

Station on Desk This photo and the one below shows the station in July 2007 prior to installation.

The cylindrical black case on top is the rainfall collector, and inverted cone that funnels water into the tipping bucket rain gauge (inside the black case). The white "accordian-like" portion below the black case is the radiation shield for the Integrated Sensor Suite (ISS) where the temperature and humidity sensors, etc. are found.

The UV and solar radiation sensors are to the side of and near the top of the black cylinder (but are difficult to see in this photo). The wind vane and anemometer are not shown.

The entire unit is powered by solar cells, with battery backup for evening, cloudy, and winter days. Communication with the console and data logger is through wireless transmission. (Photo by Johnny Lin.)
Tipping Bucket Rain Gauge The station uses a tipping bucket rain gauge. As rainfall is collected in the inverted-cone cover above, it drips down into the tipping bucket on one side of the "see-saw" above. When the bucket is filled by the water equivalent of 0.01 inches of rainfall, it tips and empties its contents. A sensor records the tipping motion as 0.01 inches of rainfall. (Photo by Johnny Lin.)

On the Roof of Helwig Recreation Center

Station on Roof This photo and the two below shows the station on August 2, 2007, after installation.

We are facing north. The black frustum is the case for the rain gauge. The station's two solar panels both face the viewer. (Photo by Johnny Lin.)
Underside of the Station This photo of the underside of the station shows the bottom of the ISS radiation shield. (Photo by Johnny Lin.)
Side View of the Station This photo of the station from the side shows the mounting tripod and how the anemometer and wind vane are extended away from the rest of the sensors. (Photo by Johnny Lin.)

View of the Station from the Ground

View from the Ground This photo was taken August 6, 2007 and shows the main (north) entrance of the Helwig Center. The station is the small, fuzzy, greyish object on the roof, directly above the Helwig main entrance. The low rectangular object that appears to be below the weather station is the outline of the air conditioning system's intake ducts, which is set back from the weather station by approximately 10 feet. The Google Maps overhead satellite image shows the position of the ducts relative to the weather station; the station is marked by the cluster of three white blocks at the north end of the building, while the ducts are the long, gray, rectangular object to the SW of the station. (Photo by Johnny Lin.)

Accuracy and Installation Notes

The accuracy values apply to the Vantage Pro2 Plus's™ outdoor sensors and were taken from the station's specification sheets; see the sheets for details and information on the indoor sensors. Notes regarding the installation are by Johnny Lin.

Parameter Accuracy and Notes
Temperature: ±1 F. At solar noon, solar radiation induces an additional 4 F error.
Humidity: ±3–4% RH
Pressure: ±0.04 in Hg
Rainfall: ±5% or ±0.04 in/hr, whichever is greater. Note that this station does not have a heater for the precipitation gauge, and so the water-equivalent of snowfall is not measured by the rain gauge.
Wind Speed: ±2 mph or ±5%, whichever is greater.
Wind Direction: ±4 deg. There is an additional error in wind direction that results from uncertainty during installation of the alignment of the wind vane with true north. This error is at least ±5 deg.

If you're interested in the maintenance log, please goto here.


Thanks to Carl Wistrom, Carl Balsam, and Bob Atkinson and his crew at Jamerson & Bauwens Electric for their help in putting up the station. Thanks to J.O. Anderson for his help in installing the replacement station and for station maintenance help. And thanks to David Frisk for helping me set-up the virtual machine and Internet access to the datalogger.

Updated: Saturday, 24-May-2014 21:40:59 PDT. Disclaimer. Valid CSS, HTML. This work is licensed under a Creative Commons Attribution-ShareAlike 2.5 License.