Experiment 1 − Measurement History

The task of the Measurement History experiment is to measure the power of the light sources by a given number of samples with a fix step size.

General description

The power which comes from a light source represents the energy radiated during a period of time.

A more detailed classification of these sources can be found at the link Light Sources.
To illustrate how the experiment works, the light bulb was chosen like light source.

Experiment Sequence

To illustrate how the experiment works, the light bulb was chosen as example.

To perform the experiment, the user has to follow the next steps:


1. Choose a light source by pressing the “Choose a light source” control (example: Light bulb).

2. Then press the “Log Config” button to choose the number of the measurements (example: 4000 samples) and the time at which the sensor should take the measurement (example: 1s).

3. Next step will be to choose the sensor by pressing the “Choose a sensor” control (example: thermal sensor).

4. Choose the distance between sensors and sources (example: 200 mm).

5. Change the intensity of the light by mowing the pointer from the “Power of the light sources in percentage” pointer slide.

6. Press the “Start Log” button to starts the measurements.
The input parameters cannot be change when the batched lab is running.

The system will start to take measurements which will be displayed on the graph in left side.

In the figure above can be seen how the radiation power of a light bulb behaves over time. Thus it can be seen that at the beginning when the light bulb is cooler and the electric current (I) is passing through the filament, the resistance (R) of the bulb is lower. The filament of the light bulb is made of Tungsten, which is a very good conductor. As the light bulb warms up, his resistance increases with the temperature but the current through the light bulb remains constant. Because of the thermal radiation process and as the bulb interacts with its surroundings over a longer time the thermal equilibrium is reached. This means that the two systems (the bulb and its surroundings) are in a stable stationary state when their temperatures are the same.

Exercises/Questions

I. Measure the power distribution over time for the LED source which is available. Export the data and plot them on the xy graph. Compere the results and write down the conclusions for the different behaviour.
II. Mesure the power distribution over time for the other sources which are available. Export the data and plot them on the xy graph. Compere the results and write down the conclusions for the different behaviour.