Special features of computer-based measurement: data-capture

• Collect data from external sensors.
• Store data in computer memory.
• Display data in graphical form.
• Process data; i.e. perform calculations.

All these tasks can, of course, be performed 'manually' by pupils and at first sight the computer merely automates the process. For many obvious reasons 'manual' measurements have had and will continue to have a dominant role in school science but it must be recognized that there are certain measurement tasks for which the computer offers special benefits which can augment rather than substitute pupils' experience. Many of the benefits arise from the computer's facilities for performing the above tasks at high speed, with large quantities of data over short or very long time periods. Through these, the computer brings certain special qualities to the process of measurement. Here are some of the special features of computer-based measurement.

Continuous recording

The rapid repetition of measurements (hundreds of values per second) can produce such a dense packing of data when plotted on the screen that it simulates the continous recording of results.

- Pupils can observe and measure rates of change
- Gradients of graphs are conveniently inspected and compared.
- Rapid changes can be precisely monitored
- Discontinuities and sudden changes are observable. e.g.Variation in air temperature with the passage of clouds

Simultaneous recording

Measurements from several sensors may be collected simultaneously (the sensors may be of similar or different types)

-Simultaneous graphs are conveniently compared.

- Links between different variables may be explored by inspection or by YX plotting.
- Displaying data while being collected reinforces the link between the experiment and the results. e.g. Temperatures inside and outside a thermal insulation jacket

Graph of data showing cooling curves

Period logging

Data may be collected over a period of hours or days

- This liberates pupils from some of the restrictions normally imposed by the school timetable and working hours.
- The data may be viewed retrospectively e.g. Plant growth, transpiration, fermentation

Graph of data from Aquarium

Remote Logging

Data may be collected independently from the microcomputer using a data-logger. - Data-logger may be sited in locations which are not convenient for computers - Computer is made free for other activity - This is well-suited to longer term experiments. - The data may be viewed retrospectively e.g. Field work: climatic factors over few hours Laboratory experiments: germination of peas etc.

Delay

A data logger may be set up so that it waits for a specified time before beginning to log data.

- Useful for starting an experiment after school hours e.g. Animal activity during night

Timing and motion measurements

Computers and data-loggers can readily perform the timing measurements required for a major area of experimental physics. Software readily converts transit times from light gates into velocities and acceleration through calculation. e.g. investigating the effect of the resultant force on a body and its acceleration.

The qualities of measurement listed here show benefits which are largely of a physical or logistical kind. Measurements with the computer are fast, plentiful, prompt and regular, and can be stored and presented immediately. Pupils can observe and measure phenomena in so much more detail compared with the use of manual techniques with conventional instruments; sometimes the computer can make visible, effects or patterns which might otherwise be invisible because they are too small, to sudden or too slow. Often pupils gain time which can be deployed on more tasks or more thought. The reliability and 'persistence' of the computer can also reduce the effects of fatigue, carelessness and impatience in pupils.

-Author-

Laurence Rogers, School of Education