Data Collection With Probes

Here is an example describing data collection using probeware. We are particularly fond of this example because we conducted the data collection in our backyard.

Using a data logger to measure stress

An interesting thing sometimes happens when powerful tools are readily available. Authentic tasks, the tasks we described in the first chapter as mimicking the activities of those we would describe as practitioners, seem to present themselves. Sometimes the tools provide the means to answer some of the questions that occur to all of us. Here is a personal example.

We know a health and physical education teacher who engages her students in projects that require the collection and analysis of data. Some of her projects use a device that records heart rate data. The device, which consists of a strap worn around the chest and a data recorder worn like a wristwatch, allows complete freedom of activity. The data recorder holds more than eight hours of information and is easily connected to a computer for data transfer. She described a project that involved the parents of her middle-school students. She asks for three parent volunteers with three different occupations who are willing to wear the heart monitor during their workday. When they can remember, the volunteers are asked to push a button on the recorder when they change activities and to keep notes identifying the different activities. The data logger marks the time when these transitions occur. Students bring the heart monitor back to school, offload the data onto a computer, create a chart from the data, and enter labels on the chart corresponding to the activities that the parents report. Students then compare the heart rate patterns of each subject and discuss which activities seemed to create the greatest stress.

We borrowed the heart rate monitor and tried to generate our own authentic investigation. Here is what we came up with. We own a hot tub (called a spa in some locations) and, in reading the operating instructions, noted some health warnings. Individuals with certain medical conditions are cautioned against using the hot tub. Remembering the description of the use of the heart monitor as a measure of stress, we wondered if sitting in 104°F water could be demonstrated to stress the circulatory system. The design of our experiment was simple: Establish a 20-minute baseline, sit in the hot tub for 20 minutes, and conclude with a 20-minute cooling-off period.

The data generated clearly demonstrate the stress heat imposes on the body. The data are graphed in the image that appears below. Note the two marks on the x-axis. These marks indicate the transitions between stages of our experiment. The middle segment of the graph, the time during which Mark was in the hot water, demonstrates an elevated and accelerating heart rate. Note irregularities in the data appearing near the transitions between stages of the experiment. During these transitions, Mark was in his swimming suit working to remove and then reattach the hot tub cover with an air temperature of 20°F.

The computer can also store the raw heart rate data as a text file consisting of the numerical values recorded by the data logger. Once this has been done, the text file can be opened with a spreadsheet, and the data can be manipulated and analyzed in various ways. For example, we selected data values for the first and second segments that did not include the irregularities associated with removing the hot tub cover. The spreadsheet average function was then applied to these two sets of numbers. The average heart rate before entering the hot water was 74 beats per minute, and the average heart rate after entering the hot water was 89 beats per minute. It appears that our hypothesis concerning the stress experienced because of heat has been supported. Many related questions might follow: Why does the heart work harder when the body temperature is raised? Would you expect heart rate to be affected in the same way on a very warm day? Who should be cautioned against spending time in a hot tub?

Information about Data Loggers, Calculator-Based Laboratories (CBLs), Microcomputer-Based Laboratories (MBLs) and probes that attach to the CBLs and MBLs can be located on the Internet. Some of these sites also sell curriculum materials related to these products. Some sources follow.

HOBO data loggers are available from Onset Computer Corporation. (http://www.onsetcomp.com).

The Polar Heart Rate Monitor is available from Heartmind Heart Rate Monitors. Software associated with this product is available for both the Macintosh and Windows operating systems. (http://www.polarusa.com/).

Vernier sells sensors, kits of sensors suited to particular math and science courses, and lab manuals describing a variety of experiments that can be performed with the sensors. The Vernier site also identifies more companies that can use these probes and this information may be useful in extending the small list we can provide here (http://www.vernier.com).