LEPLA

1. Data collection system

By the "handheld technology" we hereby mean portable, compact data-loggers with compatible sensors, controlled by and used together with programmable graphing calculators or computers. This technology gives complete data acquisition systems. The handheld technology combines both the simplicity and demonstrative character of traditional performance with effectiveness and modernity of computerised equipment. Immediate access to the mathematical tools means that sophisticated analysis becomes a natural part of students' physics. More advanced students may learn programming and develop their own experimental procedures.

sensor

data-logger
(interface)

graphing
calculator

Elements:

sensor - to interact with the environment.
data-logger (interface) - to collect and store the information.
graphing calculator - to analyse/display the data.
auxiliary hardware and software - to control, analysis, data transmission and storage.

The sensors pick up the signals following commands from the calculator by way of data-logger (the interface). The measurements may be of voltage, current, sound, magnetic field, light, distance or a number of other physics quantities. Each measurement is converted into voltage which is then transmitted back to the interface. The interface stores the voltage values and can convert them linearly, statistically or by working out time derivatives. These are sent to the calculator, when requested. Simple programs elaborated for a particular experiment and stored permanently in the calculator memory let the student plot graphs and make analysis of the data. In this way the student learns all the steps typical for advanced digital systems: calibration, choice of sampling parameters, measuring range and methods of analysis: curve fits, statistics, error estimation, plotting, etc.

2. Data acquisition procedure

loading the data acquisition application into the calculator, and start it.
choosing the sensor(s) to be used and connecting them with the interface.
setting the acquisition parameters.
collecting and saving data.

Before starting the experiment one should have downloaded the proper software application from a PC into the graphing calculator. This can be done using the GraphLink cable and the TI-Connect software. Data analysis can be started immediately when data acquisition is finished, or can be postponed to a later session. The same data logging procedure repeats identical for any of the LEPLA physics experiment.

TI graphing calculators.
The graphing calculators used within LEPLA are of the two categories:

TI84 or TI84 Plus, TI-83 Plus or TI-83SE, TI-83.
TI-89 or TI-89 Titanium, Voyager2000, TI-92plus.

The two categories have different Operating Systems and require different calculator software applications, but their performance and the general features are quite similar. A detailed guide how to use the graphing calculators is provided in each LEPLA module.

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Auxliliary calculator hardware.
There are different types of the data transmission connection facilities (calculator <--> computer):

silver GraphLink cable - USB port.
gray GraphLink cable- for Serial Port (PC and Macintosh).
black GraphLink cable - for serial port (PC only).
new generation of calculators (TI84) offers direct USB connectivity between devices.

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Interfaces (CBL, CBL2, LabPro, CBR or CBR2).
The interface converts the analog signal into its digital form. The CBL, CBL2 and LabPro are quite similar and can be interchanged in most cases. They differ in cost and performance.

CBL (Caculator Based Laboratory) is no more commercially available from Texas Instruments but it is still available in many teaching laboratories. It has 10 bit resolution, 3 analog inputs, 1 sonic input, LCD display, 1 Digital In/Out, no FLASH memory.
CBL2 superseded CBL1 is manufactured by Texas Instruments. It has 10 bit resolution, 3 analog inputs, 1 sonic input, 1 Digital In/Out, FLASH memory, no LCD display.
LabPro is manufactured by Vernier Software. It has 12 bit resolution, 4 analog inputs, 2 sonic inputs, 1 Digital In/Out, FLASH memory, no LCD display.
CBR2 superseded CBR (Calculator Based Ranger) is a specialised interface combined with the ultrasonic distance meter.

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Sensors.
Voltage, current, sound, magnetic field, position, pressure, force, light intensity, distance, temperature and many others physics quantities may be registered using the specialized sensors. All sensors are pre-calibrated but may be re-calibrated by the user through a simple two-points routine.
Most of the sensors used with LEPLA experiments are linear analog probes available as equipment developed for TI graphing calculators. All the sensors provided by Vernier Software can be used with LEPLA experiments, but also many other linear sensors may be used (provided a suitable calibration according to the software used).
There are also a few digital probes available, like the Sonar (Motion Detector) or non-linear probes (like Temperature probe). The Sonar combines the source and receiver of the acoustic wave. This digital probe must be connected to the SONIC port of the CBL/LabPro.

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Auxiliary calculator & computer software.
There are three kinds of calculator software:

Single purpose programs made by users (freely available through Internet).
Standard universal programs (freeware): Vernier Physics, DataMate, Ranger, Science.
Commercially available software: LoggerPro (for LabPro only).

There are also communication programs to transfer data between PC and calculator: GraphLink, TI-Connect Data analysis, TI-Interactive, Vernier Graphical Analysis, LoggerPro.

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