1 xx refers to the Figure number; 1 for Figure 1, 2 for Figure 2, etc.

Transcription

1 Lab Experiment No. Voltage and Current Maps I. Introduction The purpose of this lab is to gain additional familiarity with making measurements on electrical networks. The experiments involved in this lab address the following topics (a) reading and understanding a schematic diagram, (b) proper layout of a network on a breadboard, (c) application of electronic test equipment to make voltage and current measurements, (d) generation of a voltage, current, and power map of a network under test (NUT), and (e) performing the least number of measurements necessary to generate the map. The theory and equations associated with these experiments are covered in your class notes. Your job in this session is to build and apply two measurement methods on each of the given networks in order to expand your hands-on experience in working with networks and test equipment. For each network included, make use of the parts supplied by the GTA, and the DMM and dc power supply located on the lab bench. II. Breadboard construction and network measurements The schematics for three resistive networks are shown in Figures through. Node 0 is the designated ground or reference node for each network. Each network has three corresponding data tables that are to be filled out. You are to perform the following tasks. (a) Direct measurement method i. Build the network on your breadboard with particular attention paid to strict layout procedures. ii. Measure with the DMM the resistance of each resistor and record it in Table xx (a) in the column where indicated. iii. Power the network with the dc power supply set to the specified voltage indicated on the schematic. iv. Use the DMM to measure the voltage drop across each resistor and label on the schematic with a positive sign (+) the resistor s positive terminal. Record the voltage reading in Table xx(a) where indicated. v. Complete Table xx(a) entries by computing with Ohm s law the current through (use the measured resistor s in Table xx(a)) and the power dissipated by each resistor. Use KCL to compute the current through and the power dissipated by the power supply. (b) Indirect (node) measurement method i. Using the same network breadboard layout in (a), measure the voltage at each node (V ni ) with respect to the ground node (node 0 ) and record in Table xx(b) where indicated. Label on the schematic the polarity of the node voltage with a positive (+) or negative ( ) sign. ii. Apply KVL to the node voltages to calculate the voltage across each network resistor. Record the KVL expression and resistor voltage in Table xx(c). iii. Complete the entries in Table xx(c) by computing with Ohm s law the current through (use the measured resistor s in Table xx(a)) and the power dissipated by each resistor. Use KCL to compute the current through and the power dissipated by the power supply. III. An example An example network is worked with the results presented in Tables at the end of this lab statement. Node B is the designated ground node for this network. IV. Comparisons, comments and conclusions Compare the voltages, currents and power dissipation in Tables xx(a) and xx(c) for each network. Make comments on which measurement method is more efficient, practical and easier to perform. xx refers to the Figure number; for Figure, for Figure, etc.

2 Network N R K 7K 6K K R K 0V 6 N 68K Figure 0 8K Resistive network N Component R R Spec KΩ 7KΩ KΩ 8KΩ 6KΩ 68KΩ KΩ 0V Table (a) Variable map for network N from direct measurements Measured V Ri (V) I Ri (A) P Ri (W) Table (b) Node-to-ground voltages Node i V ni (V) 6

3 Table (c) Variable map for N from node measurements Component KVL V Ri (V) I Ri (A) P Ri (W) R R

4 Network N 0K R R 7K K V 0K 8K 8.K R 68K N K 0 Figure Resistive network N 9K Component R R Spec 7KΩ KΩ 68KΩ 9KΩ 0KΩ KΩ 0KΩ 8KΩ 8.KΩ V Table (a) Variable map for network N from direct measurements Measured V Ri (V) I Ri (A) P Ri (W) Table (b) Node-to-ground voltages Node i V ni (V)

5 Table (c) Variable map for N from node measurements Component KVL V Ri (V) I Ri (A) P Ri (W) R R

6 Network N R 00 V.K.K 0 V 0.7K.K 6.K.8K R 00 Figure Resistive network N Component R R Spec 00Ω 0Ω 00Ω.KΩ.8KΩ.KΩ.7KΩ.KΩ.KΩ V V Table (a) Variable map for network N from direct measurements Measured V Ri (V) I Ri (A) P Ri (W) Table (b) Node-to-ground voltages Node i V ni (V) 6

7 Table (c) Variable map for N from node measurements Component KVL V Ri (V) I Ri (A) P Ri (W) R R

8 Example Network A R 0K.K V ps 0V 6K 680 R B 6K Figure Example resistive network K Component Table (a) Variable map for the example network from direct measurements Spec Measured V Ri (V) I Ri (A) P Ri (W) R 0KΩ 9.8KΩ µ 6.µ 7KΩ.7KΩ µ 9.9µ R KΩ 67.9Ω 7.6m.µ.06µ 8KΩ 9.98KΩ.777.µ.9µ 6KΩ.8KΩ.97.6µ 9.µ 68KΩ.0kΩ µ 6.9µ V ps 0V 0.09V µ -.097m Table (b) Node-to-ground voltages Node i V ni (V) A 0.09

9 Table (c) Variable map for example network from node measurements Component KVL V Ri (V) I Ri (A) P Ri (W) R V A V µ 0.8µ V V µ 9.99µ R V V 7.6m.µ.06µ V V.777.µ.9µ V V.97.µ 9.µ V µ 6.9µ V A 0.09 (-I R ) µ -.098m