Oxygen Sensor

Feb 28, 2010

The oxygen sensor can be used to make measurements of the level of free oxygen in air or dissolved oxygen in water.

The free oxygen in air mode is used to measure changes in oxygen levels during combustion or in reactions that produce oxygen (hydrogen peroxide decomposition). The dissolved oxygen mode is useful in the study of photosynthesis. The mode is changed using the module setup option on the sensor module box in NeuLog™ software (see video) or the change range option on the Monitor Display Unit.

The operation of the oxygen sensor is demonstrated in the video below.

Oxygen Sensor from Allan Kerr on Vimeo.

The oxygen sensor is designed for use both in the school laboratory and in the field. It employs easy-to-use polarographic (Clark) technology and replaceable membranes are available. The electrode itself is constructed of Delrin® for durability. With its integral thermistor it provides dependable temperature-compensated measurements. The thermistor is housed in stainless steel and sealed on the electrode’s outer wall providing fast, accurate readings.

The installation and replacement of the membrane is quick and easy. Simply fill the membrane cap assembly with DO electrolyte and screw it into place. Two membrane cap assemblies are included with each sensor. The sensor can be stored in de-ionised water between measurements and overnight. For long term storage the membrane cap should be removed, rinsed in de-ionised water and stored dry.

Sensor Calibration

Calibration of the probe is simply achieved in open air, taking this as a standard level of 20.9%*. First connect the sensor to a voltage source (the USB Bridge plugged into a PC, Neulog’s Monitor Display Unit or Battery Unit) and wait until the reading is stabilized (about 2 minutes). Press the black button on the sensor box for about 3 seconds when the readings are stable. The sensor will then be calibrated at 20.9%.

Alternatively the sensor can be connected to a PC running the Logger Sensors software via the USB module. First click on the Module setup button on the Oxygen sensor’s Module box to open its Module setup window. Then click on the calibration icon.

*This is an assumed stable level in the Earth’s atmosphere at sea-level.

The oxygen sensor can be used in experiments from as short as 1 second and up to 31 days in duration. Sampling rates can be varied from 60 per minute up to 100 per second.

Experiment 1

After calibrating the sensor to 20.9%, I ran the following experiment. I started to breathe on the sensor and I had to breathe out quite strongly to get the oxygen level down to 20% in the 10 seconds of the experiment. The results are shown in the chart below.

Experiment 2

In this experiment we will investigate how the oxygen level in a closed environment drops as a burning flame uses up oxygen in its combustion. The experimental setup is shown below. I used a large soft drink bottle with the bottom cut off and a hole cut for the electrode. I used Blue Tack to seal the around the bottom of the bottle and around the oxygen electrode. I lit a small candle and placed the assembly over it for the experiment. I positioned the candle near the side as far away from the electrode position to avoid heating up the electrode. Although the picture below does not show this it is how I did the experiment when I found the top of the bottle heating up.

The results and observations are quite interesting. Over one minute the oxygen level in the air inside the bottle dropped from 20.9% to below 17% and the flame became weaker and weaker and finally went out after around 50seconds after which the oxygen level started to rise because I took the electrode out of the bottle. Although initially there was a linear drop in oxygen level this soon started was starting to flatten as you can see as the flame became weaker. On these findings you might conclude that the oxygen concentration needs to be above 17% or so to support combustion at least with our candle.

Experiment 3

In this brief experiment we looked at dissolved oxygen levels in cold and warm tap water. It is well-known the oxygen levels decrease as water temperature rises and we found the same here. Cold tap water had an oxygen level of 10.4 mg/l or parts per million (ppm) which is quite high and hot tap water 10.2 mg/l.

Specifications

Specifications for the electrode are as follows

New Zealand Experience with MagiClass™

Feb 27, 2010

In 2009, Training Systems New Zealand provided equipment and support for a number of trials of the magiClass™ classroom response system in a New Zealand secondary school. The school subsequently purchased a class set late last year.

The technology is designed to actively engage and involve pupils in a classroom situation and to provide immediate feedback on each student’s understanding.

magiClass™ utilises PowerPoint^® presentations with selected slides containing up to 5 multi-choice questions. Each student clicks their answer and a bar chart or pie chart overlaid on the presentation shows the distribution of answers. Individual answers are anonymous but the system keeps a record which the teacher can analyse later.

The teacher who ran one of the trials did so in a revision lesson found the following

• Preparation was quick and the technology was simple to use with no technical problems.

• The method appealed to students with a wide range of abilities.

• Participation was almost 100% and some students who normally would never participate in class became involved in class discussions held to analyse answers. The teacher concluded that these students had gained confidence when they supplied a correct answer.

• The records collected during the class showed that some areas required further teaching and identified students who needed additional assistance.

The teacher also ran a control trial with another class with the same topic and year using the same slides without magiClass™. Participation was based on a show of hands and usually less than one-third of the class responded. Mostly, it was the same few who contributed to discussion.

The key advantage of magiClass™ is clearly the ability to engage all students.

pH Sensor

Feb 25, 2010

The pH sensor can be used to measure the static pH values of common liquids (water, milk, soft drinks, vinegar, etc.) as well as the changing values in titrations or experiments such as those looking at the effect of antacids.

The pH sensor is designed for long life in a variety of general purpose situations. Its sealed reference system and gel fill make it easy to use and maintain. With an epoxy body it is a durable electrode for use both in the laboratory and in the field.

The operation of the pH sensor is demonstrated in the video below.

pH Sensor from Allan Kerr on Vimeo.

Sensor Calibration

This sensor gives a fast response across the full pH range and can be calibrated with any standard buffer solution. Connect the sensor to a voltage source (the USB Bridge plugged into a PC, Neulog’s™ Monitor Display Unit or Battery Unit), insert the sensor into a pH = 7 buffer and press the black button on the sensor and hold for about 3 seconds. The reading will then be calibrated to 7. Alternatively the sensor can be connected to a PC running the Logger Sensors software via the USB Bridge. First click on the Module setup button on the pH sensor’s Module box to open its Module setup window. Then click on the Calibration icon

The pH sensor can be used in experiments from as short as 1 second and up to 31 days in duration. Sampling rates can be varied from 60 per minute up to 100 per second.

Experiment 1

In this experiment we will investigate the pH of a range of liquids, tap water, bottled water, pool water, Coca- Cola, “V” energy drink, beer, coffee and tea.

The pH values from lowest to highest were

Coca-Cola                                                 2.2

“V”                                                              2.3

Beer                                                            3.2

Bottled water (h2go)                           6.1

Tap water (Epsom, Auckland)         6.3

Ant-acid formulation (Mylanta)    7.2

It is amazing how acidic the soft drinks and beer are. No wonder some people need to take ant-acid tablets or medicines.

Experiment 2

In this experiment we will investigate how adding ant-acid mixture to a glass of Coca-Cola raises the pH.  We gradually poured in some ant-acid solution to the Coca-Cola over a few minutes. The results on the chart below were measured over 1 minute at a sampling rate of 5 per second and showed the pH went climbing from an initial 2.1 to 4.7/4.8 as the ant-acid mixture was added. It really works!

Specifications

Specifications for the electrode

Photogate Sensor

Feb 22, 2010

The Photogate sensor is contained in a strong plastic frame with an infrared light emitting diode (LED) on one side and an infrared-sensitive phototransistor on the other side. The Photogate is used to measure the time interval during which its infrared beam is interrupted. By inputting the lengths of timing-cards (see examples below) passing through the photogate, both velocity and acceleration can be calculated from the time measurement. The Photogate sensor can be used to study various kinds of motion. With four modes of operation, time, velocity or acceleration can be measured with one or two photogates and associated timing-cards. The sensor can also show pictorially the status (digital 1 or 0) of the voltage output of the photogate as timing cards pass through it

The operation of the photogate sensor is demonstrated in the video below.

Photogate Sensor from Allan Kerr on Vimeo.

A possible experimental setup is shown below.

The Photogate sensor can be used in experiments from as short as 1 second and up to 31 days in duration. Sampling rates can be varied from 60 per minute up to 100 per second.

Digital meter mode

As well as recording time, velocity and acceleration in tables, this mode allows individual measurements to be displayed in digital form on the screen together with their units and average values for a number of runs.

Time and Velocity mode

The displayed value can be either the time taken for the timing-card to pass through the

photogate, or its velocity or both. The length of the timing-card or flag must be entered into the box above its image. Repeated passes can be made with the software recording the values and calculating an average value.

Our simple experimental setup is shown below. In this case I passed the photogate sensor over the timing card.

The results for 5 passes are shown in the table below. The digital display shows the last velocity value and automatically calculates and displays the average velocity for the 5 passes.

Acceleration mode 1

The displayed result will be the acceleration of the double timing-card passing through the photogate. The timing-card lengths must be entered in the box above their images. Repeated passes can be made and values recorded, together with an average value.

Our simple experimental setup in which I passed the photogate sensor over the card is shown below.

The results of 5 passes are shown below with the average acceleration displayed as before.

Acceleration mode 2

The displayed result is the acceleration of the timing-card passing through the two photogates. The timing-card’s flag length must be entered in the box above its image. The ID numbers of the two photogates used must be selected and entered into the two boxes indicating which is passed through first and which second. Repeated passes can be made and values recorded, together with an average value. We did not demonstrate this experiment.

Status graph mode

As a timing-card passes through the photogate a graph of its digital status (1 or 0) against time is produced. When the beam is interrupted it displays as 1 indicating a voltage output from the photogate of around 5V. When the beam is uninterrupted it displays as 0 indicating a voltage output from the photogate of close to 0V. 

Output from our experiment is shown below.

Specifications

Relative Humidity Sensor

Feb 21, 2010

The Relative Humidity (RH) sensor is shown above connected to the laptop through the USB bridge for online experiments. The RH sensor can be used to record the variation in weather conditions and used in experiments to determine effects of atmospheric conditions on such biological organisms as seedlings and insects.

Right now in February 2010 we are suffering very high humidity levels in Auckland and at times it can be very uncomfortable. So the subject of humidity is very topical right now. The operation of the humidity sensor is demonstrated in the video below.

Relative Humidity Sensor from Allan Kerr on Vimeo.

The sensor can be used in experiments from as short as 1 second and up to 31 days in duration. Sampling rates can be varied from 60 per minute up to 100 per second

Example 1

The first example is a quick experiment to show the effects of my breathing into the sensor. As you can see below there was a background RH in the office of around 74%. RH increased to above 90% when I breathed into the sensor and then RH gradually dropped back down afterwards.

Example 2

In the second experiment I decided to study the RH variation overnight in the Training Systems New Zealand office. I programmed the sensor in offline mode and then disconnected it from the USB bridge and connected it to the battery pack as shown below. I then started a 20 hour experiment with measurements very minute (60 per hour) by pressing the black button that you can see on the sensor.

The results are shown on the chart below.

The data show that the relative humidity in the office remained high at around 75% for 13 hours which was 4am when it started to fall reaching 60-65% by 11am. In the afternoon RH dropped further to around 54-55% which was much more pleasant.

Specifications

Heart Rate & Pulse Sensor

Feb 6, 2010

This sensor can be used to monitor and compare pulse rates under various exercise and rest conditions and to compare the “normal’ and “after exercise” pulse rates. Additionally it can show how blood volume and flow rates in the finger or ear lobe vary with time.

The operation of the heart rate and pulse sensor is demonstrated in the video below.

The sensors can be used in experiments from as short as 1 second up to 31 days in duration. Sampling rates can be varied from 60 per minute up to 100.

To operate the sensor, connect the clip to a finger or ear lobe and start measuring either connected via the USB Bridge to a PC, or to the Monitor Display Unit. On the PC you can choose to see the pulse wave showing changes of blood volume/flow in the finger or earlobe with time (and calculate the pulse) or get the value of the pulse rate directly via the software. The operating mode is changed by clicking on the sensor’s Module Setup button on the Sensor Module box to display the Heart and Pulse sensor module setup window, and selecting the mode as required.

For best results, the sensor should be kept away from direct sunlight and high intensity lights.

Example 1

The first example is my pulse rate while sitting at my desk. As can be seen from the chart below my pulse was steady at around 57 beats per minute which is quite low. I was much fitter a few years ago when I ran and played squash and my resting pulse was consistently below 50.

I did a little exercise walking across the room and then sat down and measured my pulse. You can see from the chart below that my pulse dropped from over 80 down to its resting rate but it was not as steady as before.

Example 2

The chart below shows my resting pulse wave or blood flow. The heart pumps blood rapidly and it then returns more slowly before the heart beats again.

Specifications

BPM = beats per minute

Specifications for the electrodes

Both are plethysmograph-based and so record changes in blood volume/flow. The sensors consist of an infrared LED transmitter and a matched infrared phototransistor receiver.

Light Sensor

Feb 1, 2010

The Neulog light sensor is located in a small plastic box accessible to the atmosphere via a hole in the top through which light intensity is sensed and measured. Like all of the Neulog sensors the light sensor is programmable and is also a datalogger able to be used in remote experiments. The sensor is demonstrated in the video below.

Like all the Neulog sensors the light sensor is connected to the computer through a USB bridge as shown below. Many sensors of either the same or different type can be connected in a string through one USB bridge.

The light sensor is very versatile with applications in many areas of the natural sciences. In biology it can be used to study photosynthesis, in chemistry to study light-emitting chemical reactions and in physics to study the effects of changing voltage on a light-bulb’s output.

With three light intensity ranges, it can be used in low light environments such as in a classroom, or in high light environments as in daylight outdoors. It measures Illumination and with both fast and slow modes it can be used to measure fast light changes such as those produced by light bulbs connected to an ac. supply, as well as the near steady levels outside on a sunny day.

The sensors can be used in experiments from as short as 50 milliseconds up to 31 days in duration. Sampling rates can be varied from 60 per minute up to 100 per second.

Example1

In the example below the Neulog light sensor has been used to measure the light intensity in the office. The peaks are when the sensor was pointed at the fluorescent lights.

Example 2

In this example the sensor has been set for the largest scale and has been used to measure the speed of development of light intensity in an infrared lamp.

On the next chart I have positioned the cursors to measure the speed with which the lamp attained its maximum intensity. This occurred in 0.53 seconds.

On the next chart I have positioned the cursors to measure the speed with which the lamp intensity reduced when the power supply was turned off. Intensity dropped to a low level in 0.23 seconds, at twice the speed that the intensity developed when we switched the lamp on.

There are of course many experiments that can be done using the light sensor. The purpose here is to outline the main functions and features of the Neulog light sensor.

Specifications of the Neulog Light Sensor

Sound Sensor

Jan 25, 2010

The Neulog sound sensor is located in a small plastic box accessible to the atmosphere via a hole in the top through which sounds are sensed. Like all of the Neulog sensors the sound sensor is programmable and is a datalogger able to be used in remote experiments. The on-line and off-line modes of operation are demonstrated in the video below.

The sound sensor has two modes of operation. In slow mode it can be used to measure sound pressure level in decibels. In fast mode it can be used to compare different sources of sound through display of their waveforms. The frequencies of tuning forks and wind-chimes can be determined and simple electronic signal generators can be calibrated using these frequencies. With two sound sensors the velocity of propagation of sound in various media can be determined by timing a pulse traveling between them.

The sensors can be used in experiments from as short as 25 milliseconds up to 31 days in duration. Sampling rates can be varied from 60 per minute up to 100 per second.

In one mode of operation The Neulog sound sensor measures the level of sound in decibels. In the second mode of operation the sensor displays sound waveforms using arbitrary units.

Example 1

The first example is the decibel level of a my voice during over a 10 second period sampling at a rate of 10 measurements per second.

Example 2

The second example is the measurement of sound waves being used to shatter a wine glass (see video).

The frequency of the sound waves can be calculated using the cursor as shown above. The distance form peak to peak for one cycle is 0.32 seconds. This means that the frequency at this particular point was 1/0.32 = 3.125 per second or 3.125 Hertz (Hz). The average frequency over the 10 second period can be measured simply by counting the peaks which depending on what you determine to be a peak is around 3.1 per second or 3.1 Hz.

Specifications of the Neulog Sound Sensor

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Jan 25, 2010

MagiClass

Dec 28, 2009

A new way of interacting with Students. Introducing MagiClass

• Extremely simple to use – interactive presentations and comprehensive reports are ready instantly
• Enables automatic data checks, such as late students
• Builds databases in real time or for later use
• Enables automatic and instant chart creation
• Enables creation and grading of personal tests
• Enables creation and assessment of surveys
• Enables the teacher to adapt the lesson in real time based on the needs of students

So how does it work? Click here to see how it works

Please view the Blog page for an article on New Zealand experience using Magiclass.