Building a Computer Based Measurement System

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Adil Elmi AVCE Science Physics Unit 13           Page         4/27/2007

BUILDING A COMPUTER BASED LABORTARY MEASUREMENT SYSTEM

Introduction:

Electric systems are made up of three main parts: input, processor and output. The input is the part that would convert the input signal to a voltage, so therefore changes the form which information is presented in. the electrical signal is then passed into the processing block, which process the input information, however the signal coming out of the processing block is still an electrical signal but it has been changed, which point to it being processed. The last part of an electric system the output responds to the processed electrical signal and changes it in the form of light, heat, sound. In electric systems the input and output use devices which convert signals from one form to another. Theses are called transducers. Transducers can be divided into input transducers and output transducers. Input transducers are devices convert physical quantity such as light and temperature levels into a voltage or some other electrical quantity. A light independent resistor is responds to changes in light intensity by changing its resistance. The change in a resistance can be used in a simple circuit to produce a changing voltage. Output transducers change electronic signal back to some form of physical quantity e.g. loud speakers converts an electronic system into changes in air pressure producing sound. Electronic systems are usually separated into two types. These two types are analogue system and digital system e.g. when a button is pressed on a keyboard, this converted digitally which then comes up in the form of text on the computer screen.

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Aim:

The aim of this assignment is to build a circuit to measure the intensity of light in both dark and light. I will show that when light falls on the LDR, its resistances will be different from when light doesn’t fall on the LDR. The level of resistance will be measured using the QBASIC program on the computer. Measuring light intensity is made by devices such as sensors and transducers. The sensor is responsive to changes in the quantity of light. The transducer converts such measurement into electrical signals, which can be fed to a computer for ...

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