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Guidad tur - handhallen teknologi |
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.
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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.
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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.
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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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