AN OPEN MICROCOMPUTER-BASED LABORATORY SYSTEM FOR PERCEPTIONAL EXPERIMENTALITY

 

Ari Hämäläinen
University of Helsinki, Department of Physics
e-mail:
Ari.Hamalainen@Helsinki.FI

 

Starting points:

 

First part of research:

® licentiate thesis (1994)

 

Second part of research:

® doctor's thesis (1998 ?)

 

One-man project ® research has been mostly laboratory work

 

Formulated requirements for hardware and software

  • H1: MBL system must be equipped with a ready-made, high-quality force sensor.

    H2: It must be possible to measure negative voltage and current.

    H3: Analog inputs must be differential.

    H4: Sampling rate for analog data acquisition must be high enough.

    H5: Analog data acquisition must have adjustable, fast and reliable triggering.

    H5: Analog data acquisition must have adjustable, fast and reliable triggering.

    S1: It should be possible to record simultaneously at least two arbitrary quantities as a function of time.

    S2: Different dependencies between quantities should be possible to be represented as a linear dependency in an appropriate coordinate system.

    S3: Any two simultaneously registered quantities A and B should be allowed to be presented as (A,B) and (B,A) graphs.

    S4: Measured data and results calculated from it should be treated equally in numerical and graphical presentation, further calculations, saving, and transferring to other programs (equality of data).

    S5: All computing methods used should be documented for the teacher and for the student.

    S6: Symbols for quantities should be used consistently in calculations that the program presents.

    S7: The number of data sets that may be held in program's memory and the number of graphs presented simultaneously should be larger.

    S8: The system should be suited for progressive learning.

  • Prototype system

     

    Development

    Some fragments of the physics curriculum of the Finnish high school were redesigned from the basis of the perceptional approach and extensive use of MBL tools. From this material a set of experiments covering the formulated requirements was selected. The prototype was developed and modified, until the test experiments could be performed with it.

    Usability and reliability of the prototype has been tested by using it on lecture demonstrations, and letting teacher students to utilize it in their laboratory exercises.

    An example of a simple VEE program, source code view. Program components (subroutines, control structures etc.) are presented as graphical objects.

    A sound intensity meter with analog output of 10 mV/dB is connected to a TES 2730 multimeter. The multimeter is read with this VEE program once per second (d, e), voltage values are converted to decibels (f), and a graph is drawn (g).

    Screenshots

    User interfaces of the application programs

     

     

    ProtoULI: simple harmonic motion

     

    ProtoMeter: studying impedance of a capacitor

     

    ProtoCard: potential in a DC circuit

     

    ProtoScope: induction voltage caused by a spark

     

    Data processing tools

    Collecting differences: average velocities in different time intervals

     

    Adjustable line: the user may grab the endpoints and the midpoint with the mouse

     

    Integral: defining impulse of force

     

    Integral: defining charges of 1 to 5 similar capacitors in parallel

     

    Picking coordinates from a graph

     

    Spectrum of a human voice

     

     

    Conclusions and findings

    At present, the prototype fulfills the formulated requirements quite well, but not perfectly. Documentation for students and teachers has not been prepared for all relevant topics. There are still combinations of quantities that can not be easily recorded simultaneously.

    There are no experiences in using the prototype in schools, so a question still remains whether a system like this is able to show its strengths there. Releasing the software in public domain will hopefully encourage its use among those teachers who already have the required hardware, since there are no additional costs. Anyone who wants to continue the research from the basis of these programs is able to do so by acquiring the VEE development system and data acquisition hardware, e.g. an ULI with set of sensors.