Blackbody Radiation
Online Laboratory and Experiments Description
Version 1.0
Author: Teodora Iulia Craciun
Villach, August 2013
Contents
1.
Introduction .............................................................................................................................. 4
1.1
Online Laboratories ........................................................................................................... 4
2.
Laboratory Equipment .............................................................................................................. 6
3.
Online Laboratory - User Interfaces ......................................................................................... 9
4.
Online laboratory – Experiments ........................................................................................... 15
4.1
Experiment 1 – Measurement History ............................................................................. 15
4.1.1
General description .................................................................................................. 15
4.1.2
Experiment Sequence ............................................................................................... 15
4.1.3
Exercises/Questions ................................................................................................. 18
4.2
Experiment 2: Intensity over distance ............................................................................. 19
4.2.1
General description .................................................................................................. 19
4.2.2
Experiment Sequence ............................................................................................... 20
4.2.3
Exercises/Questions ................................................................................................. 22
References ...................................................................................................................................... 23
Table of Figures
Figure 1 Blackbody Radiation – Laboratory Equipment ................................................................. 6
Figure 2 Heater element ................................................................................................................... 7
Figure 3 User Interface ..................................................................................................................... 9
Figure 4 User interface with input parameter................................................................................. 10
Figure 5 User interface with output parameter ............................................................................... 12
Figure 6 User Interface with the input parameters ......................................................................... 13
Figure 7 User Interface with the output parameters ....................................................................... 14
Figure 8 Power distribution over time for a light bulb ................................................................... 17
Figure 9 Inverse square low ........................................................................................................... 19
Figure 10 Power distribution over distance for a light bulb ........................................................... 21
1. Introduction
This paper presents the description of the experiments which can be performed with the remote
laboratory equipment based on the Blackbody Radiation concept. The Blackbody Radiation
laboratory was set up by a group of students from CUAS University Villach.
The content of the work is structured in four chapters plus Conclusions and References. The
Introduction part presents a short overview about online laboratories. Chapter 2 describes the
Blackbody Radiation Equipment and system. Chapter 3 provides general information about the
laboratory interface designed in LabVIEW. The experiments which can be performed to the
Blackbody Radiation laboratory are described in Chapter 4. Also an example for each experiment
is explained. At the end, Chapter 5 provides several questions and exercises, related to observed
phenomena, at which users (students or teachers) will have to answer.
1.1
Online Laboratories
“Online Laboratories allows users to perform real experiments from a remote location. This
means controlling a real hardware and retrieving real results out of the observed
phenomenon.”[1]
“A division of the laboratory type can be made between batched and interactive laboratories:
Batched Laboratory implies that the online laboratory can be used by multiple users in parallel
without reservation. This type is practicable for laboratories with a low interaction level and short
execution time.
Interactive Laboratory means that the online laboratory has a high interactivity level and is used
usually by one or a small group of users at a time. Mostly a reservation system is used to control
the access of different parties.”[2]
On one laboratory equipment several experiments can be performed. The experiments can be
classified as following:

“Observation experiments – The environment and parameters are fixed, only an
observation is possible.

Fixed experiments – The environment is fixed, but parameters and measurement options
can be changed remotely.

Adaptive Experiment – The hardware environment and parameters can be changed
remotely.”[3]
Blackbody Radiation Lab is an online laboratory which can be remotely accessed and provides
several experiments.
To perform the experiments for the Blackbody Radiation Lab, the user has to visit the following
link: http://olarex.cti.ac.at:8000/blackbody.html.
2. Laboratory Equipment
To develop the hardware system of the Blackbody Radiation Laboratory a serie of equipments
were used as can be seen in Figure 1.
Aluminum frame profile - complete Lab
Radiation Sources
Sensor
Notebook
Intelligent
black
Figure 1 Blackbody Radiation – Laboratory Equipment
The main component of the system is an aluminum structure which holds a plate with six
radiation sources, a sensor slide which consist of three different sensors and an “intelligent” black
box which contains all small devices and circuits that help to control the system components. The
software part of the remote laboratory was developed in LabVIEW and runs on a notebook which
is connected to the “intelligent” black box.
The main components are the following:
1) Radiation sources
a) Five different light sources

Energy saver bulb (11W)

LED (8.1 W; 400lm)

Halogen lamp (20W)

Regular light bulb (60W)

xxx - is an open position (does not have any light
source connected)
b) One heater element

PTC heating element covered in copper

Measure 200W

Temperature: 50º - 240º C
Figure 2 Heater element
The plate which contains the radiation sources is used for choosing the desired source. The plate
is turning in both directions: left and right, and is controlled by a DC motor.
2) Three sensors
These sensors are used to measure the radiation were order from the Thorlab Company and are
ideal for power measurements. The sensor characteristics are presented below:
a) Two photodiode sensors

S132C: λ= 700nm – 1800 nm

S130VC: λ= 200nm – 1100 nm
b) One thermal sensor

S310C: λ=190nm – 25μm
A slider which is controlled by a stepper-motor provides the measurement of the sensors during
measurement process.
Sensors direction is a linear one between 200 mm – 1000 mm.
3) The Intelligent black box
The so called “intelligent black box” is a simple box that contains all small devices which control
the system components. Some of the components are listed below:
-
Voltage regulator – control board
-
DC motor drive – control board
-
Sensor multiplexer - control board
-
DAQ NI USB-6009 – Data acquisition card
-
DC controlled Dimmer - control board
-
Stepper motor card
3. Online Laboratory - User Interfaces
The software that was used to control all mechanical and electrical components from the
Blackbody Radiation Laboratory system is Lab VIEW. Therefore the Blackbody Radiation.vi
was created to develop experiments based on the physical concept.
Blackbody Radiation Laboratory interface consists of two experiments and was programed to
measure the power distribution of the radiation sources over time and over distance (Figure 3).
Figure 3 User Interface
For a better understanding and an easier explanation of the user interface, this will be divided into
two parts: right part which consists of the input parameters and the left part which consists of the
output parameters.
The right part of the lab interface can be seen in Figure 4:
1.
2.
3.
a.
4.
c.
b.
d.
e.
6.
5.
8.
7. a)
7. b)
Figure 4 User interface with input parameter
1. Display: shows the sensor which is set to detect radiation from a light source or from the
heater element.
2. Display: shows the power measured by the sensors in real time.
3. “Choose a light source” control: choose the radiation source.
4. “Choose a sensor” control: allows the user to select one of the three sensors connected to
the system.
5. The “Power of the light sources in percentage” pointer slide: gives the possibility to
change the power of the light source.
6. “Dimmer” indicator: displays the intensity variation of the light. This indicator is
available for the light bulb and halogen lamp. A better understanding of how the dimmer
works can be found by accessing the link http://en.wikipedia.org/wiki/Dimmer.
7. a) Control box: the user is able to enter the position of the sensors.
b) “Position of the measurement” pointer slide: change the distance between the sources
and light bulb by moving the white indicator. The option which was chosen will be
automatically displayed in the control box from number 7.a).
8. “Set position” button: has to be pressed and the system will execute the command given in
section 7.
For the experiment so called “Measurement History”, the user interface was designed to measure
the power distribution over time for more radiation sources. The parameters from a. to b. are
specific for this experiment.
a. “Wave” button: set and shows the wavelength of the sensor.
b. “Log Config” button: set the number of the samples and the time.
c. “Start Log” button: the system will start to take measurements which will be displayed
on the graph from the left side of the interface.
d. “Reset/Clear” button: clear the measurements from the graph and reset the initial
condition.
e. “Quit” button: stop the measurement process in case that this is needed. Otherwise the
measurements action will finish when the system is measuring the number of samples
which was chosen at the beginning.
Figure 5 consist of the experiment plot and is located on the left side of the user interface.
Besides seeing the graph here the user can also set some characteristics and save the
measurement data.
9. Tab display: switched the input and output parameters for the different experiments.
10. Plot: displays the measurement data from one sensor and one radiation source.
11. “Export Data” button: the user has the possibility to save the measurement data in a Text
File after the measurement process is finished.
12. Scroll: options for zooming the characteristic represented on the graph.
13. Scaling buttons: the x-scale and y-scale from the graph can be modified.
14. “Log-File Path”: The user has the possibility to define the path were the measurement
data should be stored before starting to take measurements.
9.
12.
10.
13.
14.
11.
Figure 5 User interface with output parameter
The other experiment developed for the Blackbody Laboratory “Intensity over distance” allows
the user to measure the power of the radiation sources for different distances.
Figure 6 represents the right side of the user interface which was designed for the “Intensity over
distance” experiment.
1.
2.
4.
3.
a.
b.
c.
d.
5.
7. a)
6.
8.
7. b)
Figure 6 User Interface with the input parameters
The following input parameters are specific for this experiment.
a. Step size: defines the interval at which the sensor distance is changing and a new
measurement is taken.
b. Maximum distance: give the possibility to choose distance until the sensor should
move and take data before the starting the measurement process.
c. Start Batch: By pressing this button the measurement process will start with the
parameters which were already chosen.
d. Batch running: this led will turns light green when the batched experiment is running.
! The input parameters cannot be change when the batched lab is running.
Figure 7 represent the left part of the user interface, the experiment plot and other options for
zooming the characteristic represented on the graph and saving data measurements.
9.
10.
11.
Figure 7 User Interface with the output parameters
9. Tab display: by selecting the second tab (Intensity over distance) the plot from this
experiment ant the save button will appear.
10. Plot: display the measurement data from more than one sensor.
11. “Export” button: save the measurement data in an Excel document.
4. Online laboratory – Experiments
Two experiments can be done with Blackbody Radiation Laboratory, experiments which measure
the power of the radiation sources over time and over distance.
4.1
Experiment 1 – Measurement History
This subchapter introduces the theoretical information which is necessary for understanding the
experiment. An example for the experiment is given. At the end, the conclusions, the exercises
and few questions can be found.
4.1.1 General description
The Measurement History experiment shows how the radiating power from a light source
behaves in time, during a specific interval.
The power which comes from a light source represents the energy radiated during a period of
time.
The light radiation sources are divided in natural sources and artificial sources. A more detailed
classification of these sources can be found at the link http://en.wikipedia.org/wiki/Light_sources.
To illustrate how the experiment works, the light bulb was chosen like light source.
4.1.2 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:
After accessing the user interface, the following parameters has to be set:
Choose a light source by pressing the “Choose a light source” control (example: Light
bulb).
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).
! In the small window, on the bottom the total time which is needed to perform the experiment
will be automatically set. This depends also on the settings made previously.
Next step will be to choose the sensor by pressing the “Choose a sensor” control
(example: thermal sensor).
The thermal sensor was chosen because the mots power consumed by an incandescent
light bulb is emitted as heat and only 5% of the power is emitted as visible light. The thermal
sensor has a large spectrum range.
Choose the distance between sensors and sources (example: 200 mm).
Change the intensity of the light by mowing the pointer from the “Power of the light
sources in percentage” pointer slide.
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.
Measurement History
5.80E-02
5.60E-02
Power [W]
5.40E-02
5.20E-02
5.00E-02
4.80E-02
4.60E-02
4.40E-02
4.20E-02
4.00E-02
0
1000
2000
3000
4000
5000
Samples]
Figure 8 Power distribution over time for a light bulb
Figure 8 shows 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 which was explained in Course, 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.
4.1.3 Exercises/Questions
I.
Measure the power distribution over time for the other light sources which are available.
Export the data and plot them on the xy graph. Compere the results and write down the
conclusions.
4.2
Experiment 2: Intensity over distance
First this subchapter will introduce the theoretical information which is necessary for
understanding the experiment. An example for the experiment is given. At the end, the
conclusions, the exercises and the questions will be presented.
4.2.1 General description
From the theory is known that the energy which is radiated outward radially in three-dimensional
space from a source is inversely proportional with the square of the distance from the source.
This process is known as the Inverse square low. More information can be found at the following
link http://en.wikipedia.org/wiki/Inverse-square_law.
Where I – is the radiation intensity
d – distance from the radiation source until the detector.
Figure 9 represents the Invers square law with a light bulb. There can be observed that the power
radiated (P) from a light bulb is distributed over larger spherical surfaces as the distance from the
source increases.
Figure 9 Inverse square low
If will be considered that the area of a sphere (A) of radius (r) is
, then the light
intensity (I) (power per unit area) at a distance r will be:
The intensity of light or other linear waves radiating from a source is inversely proportional to the
square of the distance from the source. So, the energy or intensity of a radiation source decreases
with the factor (1/4) as the distance r from the source is doubled.






.
.
4.2.2 Experiment Sequence
For a better understanding of how the experiment works, the light bulb was again chosen as
example.
To perform the experiment, the user has to follow the next steps:
After accessing the user interface, the following parameters has to be set:
Select the “Intensity over distance” tab from the upper part of the plot.
! Wait until the input and output parameters specific for the experiment will appear.
Choose a light source by pressing the “Choose a light source” control (example: Light
bulb).
Select the step at which the sensor should make measurement “step size” control
(example: 100) and interest distance up to which the sensor should take measurements,
by pressing the “maximum distance” control (example: 1000).
Next step will be to choose the sensor by pressing the “Choose a sensor” control
(example: photodiode sensor).
Change the intensity of the light by mowing the pointer from the “Power of the light
sources in percentage” pointer slide (example: 100).
Press the “Start batch” button to starts the measurements.
The right led “batch running” will turn light green in the time when the batched
experiment is running.
! 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 plot from the
left side.
Power distribution over distance for different
sensors
6.00E-02
200nm-1100nm
700nm-1800nm
Power [W]
5.00E-02
190nm-25µm
4.00E-02
3.00E-02
2.00E-02
1.00E-02
0.00E+00
0
200
400
600
800
distance [mm]
1000
1200
Figure 10 Power distribution over distance for a light bulb
Figure 10 shows the radiation power emitted by a light bulb over distance which was measured
with all three sensors.
Since the light represents a form of electromagnetic radiation, this decreases in intensity the
further it travels from the emission point. The Invers square law is use to predict the rate of
illumination of a light source.
4.2.3 Exercises/Questions
1. How the different light sources behave over distance (measurement with the same
sensor)?
2. Which are the differences between the characteristics of a light source for different
sensors?
3. Find the differences between a light source and the heater element.
References
[1] Zutin, D. G. (2009). A Network of Online Labs based on the iLab Shared Architecture
(ISA). (Master’s Thesis). Carinthia University of Applied Sciences. Villach, Austria
[2] Niederstätter, M. (2010). Lab2go – A Repository to Locate Online Laboratories.
(Master’s Thesis). Carinthia University of Applied Sciences. Villach, Austria
[3] Niederstätter, M., Maier, C. & Zutin, D. G., lab2go –A Repository to Locate Online
Laboratories.