Measurement of the frequency of the mains using the light sensor

Apparatus

Electric light source, light sensor, data logger and graphic calculator.

Arrangement

1. Connect the light sensor to the CH1 input of the data logger.
2. Connect the graphic calculator to the data logger.

Procedure

1. Switch on the calculator.
2. Press and select the DataMate application.
3. Press to reset the program.
4. Select SETUP from the main screen.
5. _{Select MODE: TIME GRAPH using the scroll cursor.}
6. _{Press .}
7. _{Select TIME GRAPH.}
8. _{Select CHANGE TIME SETTINGS.}
9. _{Enter .0004 as the time interval between samples; press to confirm; enter 150 samples and press to confirm.}
10. Select OK twice to return to the main menu.

11. Rest the light sensor on the table or point it towards some light source- it should not be too close.

12. Select START to begin collecting data – the word SAMPLING appears on screen.
13. A graph of LIGHT INTENSITY against TIME appears on screen when the chosen experiment time has elapsed.

Sample Analysis

	Fig. A Fig. B Fig. C

1. In the graph of LIGHT INTENSITY against TIME (Fig. A), notice the cursor at X =0.0072 (base of first trough), where X in this situation represents the time axis.

2. Use the cursor key to move the cursor along the graph until one loop of the graph has been traversed and the cursor has reached the point X = 0.0172 (base of second trough) shown in Fig. B.

3. Use the cursor key to move the cursor along the graph until two loops of the graph have been traversed and the cursor has reached the point X = 0.0272 (base of third trough) shown in Fig. C.

The time to complete one full cycle is (0.0272 - 0.0072) = 0.02 s.

Since it follows that the mains frequency is = 50 Hz.