Spinning Cup Anemometer Basics

Wind speed and direction are basic parameters typically collected at weather / meteorological data collection sites. One of the most common methods for measuring wind speed is with a wind driven spinning device called a cup anemometer. The spinning cup anemometer consists of three (typically) conical shaped cups that turn when moving air impinges on the cups from any direction. As the cups spin on a central low-torque bearing suspended shaft, they move one or more magnets past a magnetic reed switch. Each time the magnet passes by the reed switch the switch contacts close, resulting in a frequency of contact closures which correlates to wind speed.

Data Logger Interface

Interface to a spinning cup anemometer is simply done with the Logic Beach data logging instruments.

The switch contacts are directly wired to an Counter type input channel (which already has an internal power supply for powering the rain-gauge switch. The logger can then be configured through the HyperWare software to sample periodically read the Counter channel's value, process it and eventually store it to logger memory.

Data Logger Program Example

To program the data logger to sample, process and store wind speed readings from the spinning cup anemometer signal, the above Program Net can be used. The program is developed graphically in HyperWare (running on a PC) then downloaded into the data logger's memory where it executes. The program functions as follows...

Every 2 seconds, the Frequency icon (which represents the hardware input channel connected to the anemometer) is sampled. This frequency is fed to a Math icon where the frequency is converted algebraically to MPH. The data then fans out and is passed to three other icons that perform an Average, Minimum and Maximum calculation every 5 minutes. The Avg, Min and Max data is then passed to Memory channel icons... indicating storage to the data loggers internal memory.

Additionally, a Probe Point icon (looks like a meter probe) which is attached to the output from the Math icon is included in the Program Net. This icon allows remote access to a logger at any time from a PC via a serial link (modem, RS-232, Ethernet, etc) and the real-time wind speed can be displayed. Display can be done on the PC screen from within the HyperWare software, graphically, numerically and/or right from the data logger's local display... if so equipped.