Proceedings of the Technical Session of Institute of Physics, Sri Lanka 13 (1997) 8-10

Use of BBC Micro Computers in Physics
B. M. A. Rodrigo and D. U. J. Sonnadara
Department of Physics, University of Colombo, Colombo 3.

Interfacing micro computers with laboratory equipment enables the control of equipment and the analysis of experimental results to be performed effectively. In this paper we discuss how this can be done for three standard laboratory experiments using a BBC micro computer. Our results show that the standard I/O ports available in the BBC micro computer and the sampling speed of the built-in ADC are quite adequate for most of the computerization requirements in a physics laboratory.

Proceedings of the Technical Session of Institute of Physics, Sri Lanka 13 (1997) 11-13

An Investigation of Digital Filtering Techniques
L. M. T. D. Fernando¹, D. U. J. Sonnadara¹ and D. N. Ranasinghe^2
1Department of Physics, University of Colombo ²Department of Statistics & Computer Science, University of Colombo

A study carried out on Digital Filtering Techniques covering signal digitization, the theory of digital filtering techniques, and the implementation of digital filters. The digitization covers theories related to signal sampling, construction of an ADC which can be connected to the parallel port of an IBM compatible computer and the usage of the unidirectional parallel port as a bi-directional communication port. Several filters of lowpass, highpass, and bandpass categories were realized and their recurrence formulae were implemented. A good approximation to the ideal situation can be obtained with higher order filters. The speed of the hardware and the complexity of the software routines are crucial factors in filter designing.

Proceedings of the Technical Session of Institute of Physics, Sri Lanka 13 (1997) 14-16

A Computerized Temperature Control System
W. A. T. Weerasinghe and D. U. J. Sonnadara
Department of Physics, University of Colombo.

The objective of this work is to control the temperature of a furnace using an IBM compatible computer. The input data to the system are temperature sensor readings taken at constant intervals. An output signal from the computer is used to control the power supply to the furnace. The temperature sensor is a thermocouple. An interface circuit amplifies and converts the sensor output to an 8 bit digital value prior to input through the printer port of the computer. The output signals from the printer port are used to control the interface circuit and the relay used for controlling the power supply. An accuracy of ±2 oC was obtained with the present setup which can be constructed for under Rs. 1000/-.

Proceedings of the Technical Session of Institute of Physics, Sri Lanka 13 (1997) 17-19

Analysis of Radioactive Substances Present in Various types of Milk Powders used in Sri Lanka
L. G. Kanchana Karunagoda and S. R. D. Rosa
Department of Physics, University of Colombo, Colombo 3

The objective of this study was to ascertain the presence of radio-nuclide in various brands of milk powder marketed in Sri Lanka. Our main aim was to detect possible presence of ¹³⁷Cs (mean life = 44 years) in the samples. Since 6% of all ²³⁵U fission produces a ¹³⁷Cs nucleus within about five minutes in a nuclear fallout, it is a particularly dangerous radioactive isotope if released in the atmosphere.

Proceedings of the Technical Session of Institute of Physics, Sri Lanka 13 (1997) 20-23

Using Top Quark for testing QCD predictions and for Searching New Physics
W. G. D. Dharmaratna
Department of Physics, University of Ruhuna, Matara

A review on the transverse polarization in strong interaction and the use of transverse polarization of top quark for testing QCD and for searching new physics is presented.

Proceedings of the Technical Session of Institute of Physics, Sri Lanka 13 (1997) 24-32

Application of Magnetic and Resistivity in the location of fractures at the Maha-Oya thermal spring ? Eastern Sri Lanka
G. M. Fonseka¹, A. Younis² and E. G. D. Dayawansa^3
1Department of Physics, Open University of Sri Lanka. Nawala, ²Department of Geophysics, University of Edinburgh, UK, ³Mini-well systems Ltd, 211A, Nawala Road, Nugegoda.

The result of a total field geomagnetic survey and a dipole-dipole resistivity survey is presented. The geomagnetic maps of residual field and differential field are based on the data acquired by two proton precession magnetometers (ppm). One auto recording magnetometer was used at a base station to monitor the diurnal variation, while other was moved to different position in the survey area of approximately 2km x 3km. The geographical positions were fixed by a satellite global positioning system (G.P.S.) All the total field maps are respectively for two magnetic sensor position of the ppm. In one the magnetic sensor was held 2m above ground and in the other 1m above the ground. The reduction to pole map is presented. These procedure makers for considerable simplification of the magnetic maps in low magnetic latitudes.