LAB2new_v1_1 - Faculty of Engineering Engineering...

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Faculty of Engineering Engineering Undergraduate Office Department of Electrical & Computer Engineering GenE 123: Electrical Engineering ME 123: Electrical Engineering for Mechanical Engineers Laboratory 2: Resistor Combinations, Resistive Sensors, and DC Circuits Contributors: DJ Brush, J Lowe, Z Zayouna Last Revision: January 2011 Source: GE 123 Laboratory Manual, JD Aplevich, JD Cross, JD Leslie, MMA Salama, 1994
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Page 2 of 12 1 Introduction In this lab you will measure the resistance of resistor combinations and a light sensor called a photo-resistor. You will build DC circuits containing one or two power supplies and multiple resistors. You will also measure voltage at circuit nodes with respect to a reference called ground . You will observe how grounding one or two nodes influences a circuit. 2 Background Please review Kirchhoff’s Current and Voltage Laws ( ) and applications to circuit analysis as presented in your lectures and course textbook. Review voltage and current division , and the equivalent resistance of resistors connected in series and in parallel . Grounding a Circuit : Grounding a circuit means to connect a node to the Earth’s surface, which defines a reference node with voltage = 0 V. Voltages at other nodes in a grounded circuit are defined with respect to ground or 0 V. Nodal or Node Voltage : Nodal or node voltage in a circuit is defined by measuring the voltage difference between a node of interest (+) and a grounded node with zero voltage ( ). Figure 2.1 shows a circuit with nodes A and B, where node B is grounded so that v B = 0 V (note the ground symbol). The Digital Multi-Meter configured as a voltmeter (VM) is connected to node A and “ground” to measure node voltage v A . Voltages across circuit devices are easily obtained from node voltages. For example, the Power Supply (PS) voltage in Figure 2.1 is given as: v PS = v A v B = v A 0 = v A . Figure 2.1: Grounded DC circuit and node voltage measurement. Resistive Sensors : Resistive sensors are devices with resistive properties that change with physical changes in or around the device. The device resistance is related or calibrated to the physical property, so that a measured resistance can be converted to the physical property. For example, thermistors are sensors used to measure temperature since their resistance is related to their temperature. In this lab you will use a photo-resistor , whose resistance depends on the amount of light entering the device. Pieces of paper will be put in front of a photo resistor to decrease the amount of light and the resulting resistance changes will be measured. ground
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This note was uploaded on 05/17/2011 for the course GENE 123 taught by Professor Dabbagh during the Spring '08 term at Waterloo.

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LAB2new_v1_1 - Faculty of Engineering Engineering...

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