1.0 INTRODUCTION
1.1 Data logger
A
data logger (or datalogger), commonly referred to as a “HOBO,” is defined as an
electronic instrument that records measurements of all types at set intervals
over a period of time.Data logging is commonly used in scientific experiments
and in monitoring systems where there is the need to collect information faster
than a human can possibly collect the information and in cases where accuracy
is essential. Data loggers can record a wide variety of energy and environmental
measurements including temperature, relative humidity, AC/DC current and
voltage, differential pressure, time-of-use (lights and motors), light
intensity, water level, soil moisture, rainfall, wind speed and direction,
pulse signals, and more. Typically, data loggers are compact, battery-powered
devices equipped with an internal microprocessor, data storage, and one or more
sensors.
The three main types of data loggers
include stand-alone data loggers, web-based data logging systems, and wireless
data nodes. Stand-alone data loggers are compact, reusable, and portable, and
offer low cost and easy setup and deployment. Internal-sensor models are used
for monitoring at the logger location, while external-sensor models (with
flexible input channels for a range of external sensors) can be used for
monitoring at some distance from the logger. Most stand-alone loggers
communicate with a PC or Mac via a USB interface. For greater convenience, a
data shuttle device can be used to offload data from the logger for transport
back to a computer. Web-based data logging systems enable remote,
around-the-clock access to data via GSM cellular, WI-FI, or Ethernet
communications. These systems can be configured with a variety of
externalplug-in sensors and transmit collected data to a secure web server for
accessing the data. Wireless data nodes transmit real-time data from dozens of
points to a central PC, eliminating the need to manually retrieve and offload
data from individual data loggers.
1.2 Sensor
A
Sensor is a device, which responds to an input quantity by generating a
functionally related output usually in the form of an electrical or optical
signal.Any device that is used to convert physical parameters into electrical
signals is called sensors. The sensors must be calibrated so that electrical
output they provide maybe used to take meaningful measurements.Sensors are used
in everyday objects such as touch-sensitive elevator buttons (tactile sensor)
and lamps which dim or brighten by touching the base. There are also
innumerable applications for sensors of which most people are never aware.
Applications include cars, machines, aerospace, medicine, manufacturing and
robotics. There are two types of sensors:
1. Sensors
that are built in to your computer
2. Sensors
that are connected to your computer by a wired or wireless connection
Some examples of sensors include a location sensor,
such as a GPS receiver, that can detect your computer's current location. A
program could then use that location to provide you with information about
nearby restaurants or driving directions to your next destination. A light
sensor installed on your computer could detect the light in your surroundings,
and then adjust the screen brightness to match it.
1.3 Why use Data Logger
in Teaching and Learning?
Nowadays
most of modern students are exposed to a huge array of stimuli from their
environment. The television, home computer, computer games, game consols, hand
held games, mobile phones and much more, leaves the modern classroom teacher
with a lot of competition for the sort of attention that will lead to a real
interest and enthusiasm for classroom learning.
In this era, computers and gadgets are highly attractive to students and
they readily adapt to become effective users of various devices that many older
individuals find particularly confronting.
This interest of students in modern interactive devices, and their ability
to absorb themselves in solving problems they find relevant, allows the
effective use of data-loggers in ascience classroom to be a beneficial
experience which can actively engage students in a process they find enjoyable
and, with the power of most software now available, present the experimental
results in various forms to allow, with teacher guidance, for an improved
understanding of how the experimental variables have interacted. With the
desire of all science teachers to encourage their students’ interest in science
and learning with the possibility that some of their students may go on to a
career with a science base, the use of the data logger in science classrooms
becomes of even greater importance.
Modern scientists rarely do any of their work
Science Teachers’ Workshop 2004 without data loggers and computers being
involved. The necessary skills, and an understanding of the reasons for their
use, are very important for all students of science. Modelling of the
techniques that are genuinely used by research scientists also has an
inspirational component for the budding scientist or a student that has a
natural empathy for the experimental process. I will suggest that, rather than
just to satisfy the minimum requirements, science teachers should actively seek
to effectively involve data-logging activities as part of their students’
science experience at all levels.
1.4 When
to use data logging in Teaching and learning?
The classroom experience for science students
needs to be diverse, particularly when it comes to:
1. Designing
and carrying out experiments,
2. Analysis,
Problem solving, and communication of an understanding based on experimental
results.
The data logger can be an
useful tool to collect and analyze experimental data, having the ability
toclearly present real time results, with sensors and probes able to respond to
parameters that are beyond thenormal range available from most traditional
classroom equipment. It is clear that in the future data loggersand the use of
computers will become natural components of a secondary science classroom as
technologybecomes even more widespread and in common use with even more
applications involved in the everydaylife of a future human. The development of
the fundamental skills involved with setting up of experimentalapparatus,
presenting data, producing an interpreting graphs, means that, at this stage,
the traditional approach to performance of experiments is still an integral
component in a teacher’s pedagogy. The
use the computer and data logger can be seen as an added bonus to enhance the
opportunities for:
1. New ways
to explore traditional themes or
2. To
perform experiments that were previously very difficult, time consuming, or dangerous.
During the workshop, certain experiments will
be used as examples to illustrate where the datalogger can be of enormous
benefit to allow for:
1. Improvements
in time efficiency
2. Clear
presentation of data to allow easier analysis and interpretation
3. Difficult
data rapidly displayed to allow clear visual interpretation of
relationship between variables
2.0 ENGAGE
1. How
energy is supply to a circuit ?
2. What
are the differences in current flow between series and parallel circuit?
3. What
will happen to resistance if the circuit is wire in series and parallel ?
4. In
what way does the series circuit reduce the resistance?
5. How
to build wire in parallel and series circuit?
3.0 EMPOWER
Title
The relationship
between voltage, current and resistance (Ohm’s Law)
Objectives
To
experimentally verify Ohm’s Law through measurement and to confirm findings by
comparing measured values with prediction.
Introduction
When a battery is connected to a circuit
consisting of wires and other circuit elements likeresistors and capacitors, voltages can develop across those elements
and currents can flow through them. In
this lab we will investigate three types of circuits: those with only resistors
in them and those with resistors and either capacitors (RC circuits) or
inductors (RL circuits). We will confirm
that there is a linear relationship between current through and potential
difference across resistors (Ohm’s law:
V = IR). We will also measure the
very different relationship between current
and voltage in a capacitor and an inductor, and study the time dependent
behavior of RC and RL circuits.
Theory
Ohm’s law states that in a resistive
circuit, when the resistance is kept constant, the current through the resistor
is directly proportional to the voltage across the resistor.
This is given by the formula:
V = I x R
This can also be written as:
R = V/I
Thus, if voltage was plotted as a
function of the current (voltage on ordinate and current on the abscissa), an
ohmic resistor would yield a linear plot with slope equal to the resistance
value. Ohm’s law may be easily verified in the lab by setting up a simple
circuit consisting of a power supply that will supply the voltage, a
non-variable resistor and connecting wires. An ammeter can be added in the circuit,
in series with the resistor, to measure the current flowing through the
circuit. A voltmeter can be added parallel to the resistor in order to measure
the voltage across the resistor. The current and reading measurements taken by
the ammeter and voltmeter can be plotted as described and if the graph obtained
is linear, with slope close to the resistance value, then Ohm’s law will be
verified for R1.
Measuring Instrument
1.
Voltage/Current
Sensor PS-2115
2.
Xplorer
GLX PS-2002 or other PASPORT Interface
3.
CASTLE
Kit EM-8624A
4.
Crocodile
clips
5.
11.2
ohm Resistor
6.
Batteries
(D Cells)
Procedures
1.
Connect
the PASPORT Interface to the USB port of the computer and plug the
Voltage/Current Sensor into the PASPORT Interface.
2.
Construct
a simple series circuit with the empty battery holder, long bulb in socket, and
voltage/current sensor (see photo below).
3. You
are now ready to begin collecting data.
Data
Collection Procedure:
1. Make
sure you have good connections at each junction in the circuit.
2. Place
one D cell in the battery holder; the bulb should light. If not, troubleshoot
your circuit for a complete conducting path.
3. Click
Start and note the readings on the voltage and current digits displays.
4. Record
the voltage and current in the data table.
Data/ Results
Part
1 Resistance = 11.2 ± 0.1 Ω
|
|
DataStudio
Slope: 10.8 ± 0.59 Ω
|
|
Measured
Values
|
|
Voltage
(Volts)
|
Current
(Amps)
|
0.352
|
0.031
|
0.364
|
0.032
|
0.374
|
0.034
|
0.394
|
0.034
|
0.403
|
0.038
|
0.439
|
0.04
|
0.451
|
0.041
|
0.475
|
0.042
|
0.509
|
0.046
|
0.548
|
0.049
|
Graph 1: A plot of Voltage as a function
of Current, for the circuit with R1 = 11.2 Ω (Part 1).
Also shown is a linear fit to the plot. The
slope from the line of best fit of this plot is the measured value of R1 in the
circuit, as analyzed by the excel graphing software. This analysis was also
done in the lab using DataStudio which also yielded a value of the slope, as
analyzed by the DataStudio graphing software. These values are tabulated below.
Ideally, all three processes of
calculating R1 should have given the same value. If we consider the ohmmeter
reading as most accurate, then any variation from the ohmmeter reading can be
due to errors in the experiment when collecting data. This is expected because
the current values were not entirely stable, which may be because the current
sensor was not operated at its optimum current measurement range. This may be
seen as a slight spread in the points in graph 1. Both DataStudio and Excel
plotted identical data points and should ideally give the exact same linear
fits. Any variation in the slope values from DataStudio and Excel indicates
slight differences in the way each software processes the data and calculates
the slope. It is not easy to say which software is correct hence the ohmmeter
reading of the resistance was considered as the “correct” value of R1. Thus, percentage
error analysis was done with the ohmmeter reading of R1 as the reference.
Conclusion
The value voltage range in a circuit
will be linear with the value of resistor chosen, and perpendicular with the
value of current resulted.
4.0 ENHANCE
4.1 Ohm’s Law
4.1.1 History of Ohm’s Law
During
the nineteenth century so many advances were made in understanding the
electricalnature of matter that it has been called the “age of electricity.”
One such advance was made by an investigator named Georg Simon Ohm. Ohm was
interested in examining the relative conductivity of metals and in
investigating the relationship between the electromotive force (potential
difference) and the current in a conductor.
By taking wires made from different materials but having the same
thickness, passing a current through these wires and measuring the
electromotive force (i.e., the potential difference between the ends of the
conducting wire), he was able to experimentally determine the relative
conductivity of certain metals such as silver, copper, and gold. In another
experiment using a piece of apparatus that he built himself, Ohm investigated
the effect of current in a conductor on the voltage drop across the conductor.
He found that for a given conductor the voltage drop was directly proportional
to the current in the wire. When voltage is plotted against the current in a
given conductor, the data can be fitted to a straight line, the slope of which
is the resistance of the conductor. This result was published in 1826. In
recognition of Ohm’s work, this empirical relationship bears his name.
4.1.2 Principles
Ohm’s
Law can be written algebraically as V = IR , where V represents the potential
drop across the conductor (measured in volts), I the current in the conductor
(measured in amperes), and R the resistance of the conductor measured in units
called “ohms” (symbolized by Ω)
4.1.3 How voltage, current,
and resistance relate
An
electric circuit is formed when a conductive path is created to allow free
electrons to continuously move. This continuous movement of free electrons
through the conductors of a circuit is called a current, and it is often
referred to in terms of ‘flow’, just like the flow of a liquid through a hollow
pipe. The force motivating electrons to ‘flow’ in a circuit is called voltage.
Voltage is a specific measure of potential energy that is always
relative between two points. When we speak of a certain amount of voltage being
present in a circuit, we are referring to the measurement of how much potential
energy exists to move electrons from one particular point in that circuit to
another particular point. Without reference to two particular points, the term
‘voltage’ has no meaning Free electrons tend to move through conductors with
some degree of friction, or opposition to motion. This opposition to motion is
more properly called resistance. The amount of current in a circuit depends on
the amount of voltage available to motivate the electrons, and also the amount
of resistance in the circuit to oppose electron flow.
Just like voltage, resistance is a quantity relative between two
points. For this reason, the quantities of voltage and resistance are often
stated as being ‘between’ or ‘across’ two points in a circuit. To be able to
make meaningful statements about these quantities in circuits, we need to be
able to describe their quantities in the same way that we might quantify mass,
temperature, volume, length, or any other kind of physical quantity. Here are
the standard units of measurement for electrical current, voltage, and
resistance:
Quantity
|
Symbol
|
Unit
of Measurement
|
Unit
Abbreviation
|
Current
|
I
|
Ampere
(Amp)
|
A
|
Voltage
|
E or V
|
Volt
|
V
|
Resistance
|
R
|
Ohm
|
Ω
|
The ‘unit abbreviation’ for each quantity represents the
alphabetical symbol used as a shorthand notation for its particular unit of
measurement. Strange-looking ‘horseshoe’ symbol is the capital Greek letter.
Each unit of measurement is named after a famous experimenter in
electricity: The amp after the Frenchman Andre M. Ampere, the volt after the
Italian Alessandro Volta, and the ohm after the German Georg Simon Ohm. The
mathematical symbol for each quantity is meaningful as well. The ‘R’ for
resistance and the ‘V’ for voltage are both self-explanatory, whereas ‘I’ for
current seems a bit weird. The ‘I’ is thought to have been meant to represent
‘Intensity’ (of electron flow), and the other symbol for voltage, ‘E,’ stands
for ‘Electromotive force.’ The symbols ‘E’ and ‘V’ are interchangeable for the
most part, although some texts reserve ‘E’ to represent voltage across a source
(such as a battery or generator) and ‘V’ to represent voltage across anything
else. All of these symbols are expressed using capital letters, except in cases
where a quantity (especially voltage or current) is described in terms of a
brief period of time (called an ‘instantaneous’ value).
For example, the voltage of a battery, which is stable over a long
period of time, will be symbolized with a capital letter ‘E,’ while the voltage
peak of a lightning strike at the very instant it hits a power line would most
likely be symbolized with a lower-case letter ‘e’ (or lower-case ‘v’) to
designate that value as being at a single moment in time. This same lower-case
convention holds true for current as well, the lower-case letter ‘I’
representing current at some instant in time. Most direct-current (DC)
measurements, however, being stable over time, will be symbolized with capital
letters.
In the above circuit, there is only one source of voltage (the
battery, on the left) and only one source of resistance to current (the lamp,
on the right). This makes it very easy to apply Ohm’s Law. If we know the
values of any two of the three quantities (voltage, current, and resistance) in
this circuit, we can use Ohm’s Law to determine the third.
Relationship
between current and voltage when a resistor follows Ohm's Law
The greater the number of
ohms, the greater the resistance.The equation below shows the relationship
between voltage, current and resistance: potential difference (volt, V) =
current (ampere, A) × resistance (ohm, Ω ).
The
current flowing through a resistor at a constant temperature is directly
proportional to the voltage across the resistor. So, if you double the voltage,
the current also doubles. This is called Ohm's Law. The graph shows what
happens to the current and voltage when a resistor follows Ohm's Law.
4.2 APPLICATIONS
4.2.1 Application of Series and
Parallel Circuit in Our Daily Life.
Every day, millions of people
use various electrical appliances, such as lamps, television, radio and
computer. All these electrical devices need a continuous flow of electric
current to function. Batteries and generators provide the electricity and
electrical circuits provide the paths along which the current flow. All this
are related to the Ohm’s law which is given by:
V= IR
Where V is the potential
difference between two points which include a resistance R.Iis the current flowing
through the resistance.
There
are simple circuits and complex circuits of various types, but an electrical
circuit is basically any path through which electric current, or electrons can
flow. A flashlight is an example of a simple circuit. When the flashlight is
switched on, the current flows from the battery through the wires to the bulb,
which lights up and then back to the battery. When the flashlight is switched
off, there is a gap in the path and the bulb does not light up.
There
are few examples of how we apply series circuit in our daily life. One of the
examples is Christmas tree light bulb. The strings of tree lights used to be
wired in series.Series circuits also were formerly used for lighting in
electric multiple unit trains. For example, if the supply voltage was 600 volts
there might be eight 70-volt bulbs in series (total 560 volts) plus a resistor
to drop the remaining 40 volts. Series circuits for train lighting were
superseded, first by motor-generators, then by solid state devices.
1. Voltage
Sources in Series
Voltage sources can be
connected in series to provide a higher or lower total (resultant) voltage than
one of the sources provides alone. The resultant voltage of more than one
voltage in series depends on the values of each voltage and whether
they“series-aid” or “series-oppose” each other. The example for this voltage
sources in series is in battery or cell. A cell is a single voltaic device that
converts chemical energy to electrical energy. A familiar example of cells is
the cells you put into your flashlight. Typically,these are 1.5-V cells.A
battery is simply two or more cells interconnected and put into one package.While,
a familiar example of a battery is the 12-volt automobile battery. It
is comprised of two 6-volt cells, interconnected and packaged in one battery
case.
2. Voltage Divider
A voltage divider is a simple
circuit consisting of two resistors that has the useful property of changing a
higher voltage (Vin) into a lower one (Vout). It does this by dividing the
input voltage by a ratio determined by the values of two resistors (R1 and R2)
This circuit is best for
low-current applications like sensor and data lines. If you draw too much
current through Vout it will affect the output voltage. Therefore this
shouldn’t be used for high-current applications like power supplies (voltage regulator) are a much better
options.
To pick resistors, use the following equation:
Because the output voltage
depends solely on the ratio of R1 to R2, you could use a number of different R
values to get the same output (for example, if R1 = R2, the output will always
be half of the input, whether R is 1 Ohm or 1M Ohms). For most of our purposes,
the total resistance (R1 + R2) should be between 1k Ohms and 10k Ohms. Less
than that and the circuit will waste a lot of power flowing through R1 and R2
to ground. More than that and Vout may not be able to source enough current to
drive an analogue input. This circuit is very useful for turning the output
from a resistive sensor (such as a themi stor or force-sensitive resistor) into a voltage you can measure
using an analogue to digital converter. R2 will be your sensor and a good rule
of thumb is to choose R1 to be halfway between the lowest and highest
resistance values of the sensor.
3.0 Electrical Appliances
Other
than that, Ohm’s law also was applied to our household electrical appliances because
as we knew the current in a circuit is affected by the resistance.Resistors are
often used in the circuits of electrical appliances to affect the amount of
current that is present in its various components. By increasing or decreasing
the amount of resistance in a particular branch of the circuit, a manufacturer
can increase or decrease the amount of current in that branch. Kitchen
appliances such as electric mixers and light dimmer switches operate by
altering the current at the load by increasing or decreasing the resistance of
the circuit. Pushing the various buttons on an electric mixer can change the
mode from mixing to beating by reducing the resistance and allowing more
current to be present in the mixer. Similarly,turning a dial on a dimmer switch
can increase the resistance of its built-in resistor and thus reduce the current.
4.3 MORAL VALUES FROM OHM’S LAW
If we
really understand what is Ohm’s Law and known when is it apply we can safe
electric use at our home. For example, we want to buy electric kettle. Then we
have to choose the kettle that low power. Means that the resistance in the
kettle is low then power also low. With the low power we can save our
electricity. Besides that, we become more appreciate the Ohm’s Law because it is
an experimental result that applies to many materials but is not as universal
as say, Newton’s second law. We also become more creative and innovative
person. This is because we can manipulated the formula of Ohm’s Law, where
V=IR. In the experiment, we can increase the resistance and see what will
happen to the voltage and vice versa. By applying the Ohm’s law, one can
determine how much voltage is used in the circuits or how much current can be
applied, or what kind of resistance will be used. If the Ohm’s Law does not
exist do the electric will be perfect?.Ohms Law is the a foundation stone of
electronics and electricity.Without the Ohm’s law, there will be no electricity
at all. Therefore, the major importance of this law is that, it allows us to
enjoy the uses of our appliances now such as TV, refrigerator, Players, etc.
5.0 ADVANTAGES OF DATA
LOGGING
1. Speed
of Capture. Data logging allows the monitoring of variables within a very small or very large timescale. Computers can
capture data much faster and much more frequently than by hand. This allows for
greater accuracy and precision. In
addition, computers can process enormous amounts of data very rapidly.
2. Ease of
Capture. Valuable teaching time can be taken up with reading instruments and
writing lists of data. The use of dataloggers makes the capture of this data
far less tedious and puts science teaching in a more modern setting as a
sequence of readings can now be obtained automatically under the control of
computer software. This increases the productivity of the class and encourages
higher quality work. As pupils and teachers become confident in the use of
sensors and modernprogrammes, they are encouraged to take decisions and to
investigating the results by altering some of the variables in the experiment.
More cycles of “predicting and
testing
of hypotheses” are possible due to ease of capture of data and the saving of time
allowed by the datalogging approach to science teaching.
3.
Better learning outcomes. In the data logging approach to teaching, there is a
shift ofmphasis from gathering data to
more interpretative student activity. The simultaneous presentation of a graph
as students watch their experiment has the potential to help them relate the
graphical image to the observed experimental events. This assists in the linking of the abstract
and the concrete. Since the datalogging system can take the necessary readings
and do the calculations, the mental work for the pupils may be devoted to understanding
the experiment and exploring how the outcomes relate to the science questions
being considered. Thus, the quality of the learning experience is enhanced due
to the provision of an exciting and motivating environment.
4.
Presentation of data. With the aid of datalogging software, the data can be
easily manipulated and presented in the form of clearly drawn graphs. Real-time
datalogging presents the graph on the screen “as it happens” and this is
especially beneficial to the less able student. Various statistical functions
can be carried out easily on the data.
5.
Appreciation of modern technology. Computer technology is widely used in modern
industry for data-gathering purposes. It is important that students get an insight
into how scientists work and this should be reflected in the classroom. Knowledge
and familiarity with new technologiesis an important dimension of careers in
the technological industries and it is important that students are equipped for
the technology-rich world in which they live.
6.
Increased level of interest among students. In general, students find
information technology to be a good stimulus for learning. Software tools for
calculation and analysis reduce tasks
considered to be tedious and repetitive into creative opportunities for
carrying out investigations in the laboratory. This is often referred to as
“bringing science teaching into the twenty-first century”.
7.
Active learning is encouraged. The use of computer data logging helps to
develop problem-solving skills and encourages students to question, predict and
hypotheses about the results of their laboratory practical work. Students are
involved in planning experiments, measuring variables, analyzing results, and
evaluating experimental methods. All of these processes are at the heart of
good science teaching.
8. Mixed
ability teaching. Weaker students benefit from automated graph drawing as the
reduced effort in obtaining graphs, gives pupils of lower ability better access
to this visual medium for analyzing data. Pupils of higher ability can manipulate
the data, present it in a variety of ways, change variables and predict the
effect of these changes. In addition
they can compare their data with their colleagues and with sample data and go
on to discuss why differences exist.
References
Electricity. Retrieved from http://www.powerkuff.com/Download_Electricity.pdf
on November 20, 2012.
Electrical Resistance (Ohm’s law).
Retrieved from http://en.wikipedia.org/wiki/Series_and_parallel_circuits on
November 23, 2012.
It All About Circuit. Retrieved
from http://www.allaboutcircuits.com/vol_1/chpt_2/1.html
on November 23, 2012.
Mike Grusin (2010). Voltage
divider. Retrieved from http://www.sparkfun.com/tutorials/207 on November 23,
2012.
Series and parallel circuits.
Retrieved from http://en.wikipedia.org/wiki/Series_and_parallel_circuits on
November 20, 2012.
Voltage divider. Retrieved from http://en.wikipedia.org/wiki/Voltage_divider
on November 21, 2012.
Why is ohm’s law importance.
Retrieved from http://www.knowswhy.com/why-is-ohms-law-important/
on November 23, 2012.
Why do I need data logger.
Retrieved from http://www.ksecorp.com/products/WhydoIneddtouseDataLoggers.htm
on November 22,2012.
Why use data logging in Primary School .
Retrieved from http://www.iconic.sg/whyuse_datalogging_primary.pdf
on 22 November,2012.
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