CWX -- Current Weather

For a two-credit independent study in Atmospheric and Oceanic Sciences (AOS699) I have written software to log and display wind data from the instruments currently on the roof of the AOS building. My advisor is Prof. Charles R. Stearns.

Background:

Software and hardware existed in 1992 to log the same data on the roof of the AOS building. It was written for an independent study (AOS699) by James F. Leffel in 1993. A lightning strike on 05 August, 1996 took this system out of service. Replacement hardware (a Keithley-Metrabyte DAS-16G A/D board) was purchased to replace the lightning damaged hardware. The new hardware was not put in place because of software interface differences, time constraints, etc.

My project:

I have written software to interface to the new hardware and to log and display data. My language of choice is Tcl/Tk. A few of the numerous reasons for my choice include ease of GUI development, availability for the PC/win95 platform, availability: free. This data is available immediately on the screen of the PC located in the 14th floor map bay and is simultaneously available on the web. Data is also logged every one minute (adjustable) and log files are rotated daily.

The web server is the same PC which reads the A/D values. It is currently located at the following URL: http://aosdata.meteor.wisc.edu. This site may be in and out of service at any given time, and without warning, as I am in the development stages.

Various other pieces of software have been chosen to make this machine as functional as possible. A list can be found at the following URL: http://www.cs.wisc.edu/~timc/aos699/software-sources.html .

Similarly, a log of progress and problems encountered can be found at this URL: http://www.cs.wisc.edu/~timc/aos699/log.html .

The theory of operation behind this program can be found at the follwoing URL: http://www.cs.wisc.edu/~timc/aos699/theory.html .

Data input

Data comes from a variety of sensors and instruments on the roof of the building. The A/D board samples voltages (or voltage from a bridge as a function of instrument resistance) from the instruments, converts it to a digital value and gives the value to my program. The program then converts the data to a useful value, displays it on the screen and on the web. Data sources are:

Channel	device	measures	output type	gain
0	thermistor	roof temperature	voltage from bridge	10
1	thermistor	street temperature	voltage from bridge	10
2	??	relative humidity	Vaisala	10
3	anemometer	wind speed	??	1
4	wind vane	wind direction	voltage from bridge	1
5	pressure sensing unit	barometric pressure	voltage from bridge	1
6	??	supply voltage	1.4V power supply	1
7	jumper for zero reference	ground	0	1
counter	tipping-bucket rain guage	rain accumulation in 1/100 of an inch	N.O. contact	N/A

We have the ability to add up to 16 more bipolar channels should the need arise.

Data output

Multiple environment variables are measured by this system, and others can then be calculated from these variables.

value	units	using
roof temperature	degrees C, F	thermistor on roof
street-level temperature	degrees C, F	thermistor 3m above street
relative humidity	%	??
station pressure	mb, inches Hg	pressurer sensing unit
wind speed	m/sec, mi/hr	anemometer
wind direction	degrees reference to north	wind vane

Year 2000 compliance
As I expect this hardware and software to serve the department into the future with a minimum of maintenance, I have considered the "year 2000 problem" in program design. Data is stored, tagged with a time. This is the Tcl "clock seconds" output, given in number of seconds since January 1, 1970. All time references are with respect to "clock seconds" which eliminates any problems caused by the change to the year 2000.

This document last modified: Wed May 6 12:16:41 CDT 1998 by Tim Czerwonka, timc@cs.wisc.edu

CWX -- Current Weather

Background:

My project:

Data input

Data output

Year 2000 compliance