E-PORTFOLIO

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

Mixer Light Dimmer Switch

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.

E-PORTFOLIO

Pages

Saturday, 8 December 2012

Monday, 3 December 2012

Reflection

Presentation 3

Sunday, 2 December 2012

Data logging - Ohm's Law