Logging in the lab

Introduction

This experiment is adapted from the Advancing Physics course 
(Activity 10D from chapter 2 : sensing).

You may be being watched! You are not alone! You are surrounded by sensors in everyday life. Many, like temperature sensors in washing machines and cookers, keep things under control so that you do not have to bother. Some like movement-sensitive systems on a house or block of flats, turn on the outside lights when you arrive home, or detect possible intruders. Some, like acceleration sensors in a car, wait to trigger off an air bag for your safety if the car should crash. Some, like the sensor in a television set or video, wait on your command.

Equipment required

• DrDAQ data logger connected to a PC
• One 10k linear potentiometer
• Rubber bung for attachment to potentiometer

By collecting data from four of the sensors on the DrDAQ data logger over a period of time, we could for example monitor a classroom for changes in light level, temperature, sound level and by using the change in resistance of the potentiometer also know whether the door had been opened or closed.

Experiment setup

• Securely attach the potentiometer to the rotating part of the door damper system make sure that as the door opens the bung and therefore potentiometer shaft rotates. (In the photograph below the base of the potentiometer is glued to a small block of wood, and the bung is wedged tightly against the door damper.)
• Connect the potentiometer to the Resistance and Ground terminals on the DrDAQ.
• Plug the DrDAQ into the back of your PC, Switch your PC on and run the Picolog software.
• Setup PicoLog to record 120 samples one every second.
• Setup PicoLog to monitor Sound Level, Temperature, Light Level and Resistance.

Carrying out the experiment

Start PicoLog collecting the data. At the end of the monitored period of time you will be able to analyze your results by clicking on View Graph. The four lots of data can all be displayed on one graph or separately. You will be able to see quite clearly how sound, light and temperature levels changed and how often the classroom door was opened and closed and at what time.

Results

From this graph we can clearly see that the door was opened and allowed to close twice. Also sound levels correspond to activity within the classroom, temperature remained more or less constant and the increase and decrease in light levels correspond to blinds being opened and then closed again.

The example raises several important questions:

• What are sensors?
• What sort of things can they do?
• How do they do it?
• How can they make use of the information they generate?
• Why might sensors be important to society?

Some other things to think about:

What would you think about a ‘Smart House’ that could respond to changes in conditions? What would you want it to do? What would you not want it to do?

What sensors would be needed on a space craft, for an industrial robot or for an incubator for premature babies? What other examples can you think of?

Outcomes

1. You will have had a first acquaintance with different kinds of sensor and their uses.
2. You will have seen that sensors need to use electric circuits and display devices
3. You will have started to think about the variety of possibilities for automatic sensing
4. You will have begun to think about consequences for a society in which sensing plays an important role.