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Transcript

Fundamentals of Wireless and Routing Technology Lab 1 Analysis and Troubleshooting Basic Electric Circuit Objective : To gain experience in troubleshooting Electric Circuit. Equipment : 1. DC Power Supply. 2. VOM or DMM or Scope. 3. Power leads, breadboard, lab kit, connecting wires. Lab 1 – Pre – Lab For the circuits shown, calculate the values shown in the tables below. Show all your calculations. Table 1:It VR1 R1 1 Quantity 2 8.2kΩ V2 10 V VR2 VR3 R3 4 R2 3.3kΩ 3 1.5kΩ Circuit 1 Calculated (Ohm’s Law) Calculated using Voltage Divider Rule RT IT VR1 VR2 VR3 Table 2:Quantity It 5 V1 10 V Ir1 R1 8.2kΩ 6 Circuit 2 Ir2 R2 3.3kΩ Ir3 R3 1.5kΩ RT IT VR1 VR2 VR3 IR1 IR2 IR3 1 Calculated using Ohm’s Law Calculated using Current Divider Rule Table 3:It Ir1 12 R2 3.3kΩ VR2 R1 8.2kΩ V3 10 V 10 R3 1.5kΩ VR3 11 Cricuit 3 Quantity RT IT VR1 VR2 VR3 IR1 IR2 IR3 Calculated Table 4:It 8 R1 6 1.5kΩ R2 3.3kΩ V4 10 V 7 R4 1.5kΩ Circuit 4 5 Quantity RT IT IR1 R3 8.2kΩ IR2 IR3 IR4 VR1 VR2 VR3 VR4 Calculated Part A – Series Circuit Procedure : 1. Construct the circuit shown below and adjusted to be exactly 10 V using a VOM or DMM. 2. Enter your calculated values from Pre-lab in Table 1 on the next page. 2 Table 1:R1 4 3 Quantity 8.2kΩ V1 10 V R2 3.3kΩ V R3 1 2 1.5kΩ Fig 1 Calculated Measured (Enter Pre-Lab) Calculated using Voltage Divider Rule RT IT VR1 VR2 VR3 3. Now measure the voltage drops on each of the 3 resistors and enter into the measured values section of the table. 4. Compare the measured values with your calculated values. Do they agree? If not, then either your measured values are incorrect or the calculated values are wrong. Recheck and repeat steps 2 and 3 until your measured and calculated values are the same. 5. Add up your calculated and measured voltages. According to the kirchoff’s voltage law the sum of all voltage drops must equal the applied voltage E. Is that true in your case. Comment on your result. 6. Indirect Measurement of Current 8 R1 7 8.2kΩ V2 10 V R2 3.3kΩ 11 V 6 R3 5 1.5kΩ Fig 2:- Break Simulation Measure the voltage drop on any one of the 3 resistors and divide this measurement by the value of the resistance. Since current is the same throughout a series circuit, it doesn’t matter which resistor you use. This is just an application of OHM’s law. To 3 improve the accuracy of this measurement, measure the actual value of the resistor. This indirect measurement technique for current is much more useful and easier to perform then breaking the circuit and inserting an ammeter. Use it from now on for measuring current unless told otherwise. 7. Compare the measured and calculated current values. 8. Simulate a break in the circuit by removing the wire between R2 and R3. 9. Measure IT, VR1, VR2 and VR3. As well as the voltage across the break. To measure the voltage across the break, connect voltmeter between R2 and R3. 10. Enter your results in the table below. Simulated Break Results IT VR1 VR2 VR3 11. Based on your observations of the result above, state 3 most important facts about open circuit faults in a series circuit. 12. Use voltage divider rule to calculate VR1, VR2, VR3. Show your calculations. Compare these calculated values with the values calculated in step 2. And your measured values. Do they match? Comment. Part B – Parallel Circuit Procedure : 1. Build the circuit shown below and adjust the power supply to be exactly 10V. It 10 V3 10 V R1 8.2kΩ R2 3.3kΩ R3 1.5kΩ 9 4 2. Enter your calculated values from Pre-Lab for this circuit in Table 2 below. 3. Measure IT, VR1, VR2, VR3, IT1, IT2 and IT3. Enter your measurements in the table. Quantity Table 2:Measured Calculated using Current Divider Rule Calculated Fault Simulated Values IT RT VR1 VR2 VR3 IR1 IR2 IR3 4. Your calculated and measured values should agree. If not, repeat steps 2 and 3 until they match. 5. Add up I1, I2 and I3. According to KCL the sum of all branch currents must equal I T. Verify KCL for both the calculated and measured values. 6. Knowing it, use current divider rule to calculate branch currents, I1, I2 and I3. Compare with calculate values in step 2 and measured values in step 3. 7. Simulation of Open Circuit Fault in a Parallel Circuit Original circuit is redrawn below. 2 V1 10 V A R1 8.2kΩ R2 3.3kΩ 3 A B 1 R3 1.5kΩ B Introduce a break at point A (You can do that by either lifting the resistor at point A or by removing the wire that connects the bottom bus to R2 at A). 8. Measure IT, I1, I2, I3, VR1, VR2 and VR3. Enter these values into the table. 9. Based on your simulated results, state 3 basic facts about open circuit faults in Parallel circuit. 5 10. Can you introduce a short across points A and B? (Don’t try to do that). What will happen? Part C – Series Parallel Circuit Procedure: 1. Enter the calculated values from Pre-Lab for this circuit in Table 3 below. Table 3:It 3 Ir1 V1 10 V R1 8.2kΩ Ir2 R3 3.3kΩ VR2 2 Ir3 R2 1.5kΩ VR3 1 Calculated Measured RT IT VR1 VR2 VR3 IR1 IR2 IR3 Fig 1. 2. Set E = 10V. Measure the values of VR1, VR2 and VR3 and enter in the table. Add up V2 and V3. Comment on your results. 3. Using the current measurement technique of Lab # 3, find the measured currents in branch 1 (I1), and branch 2 (I2). Add I and I2 together, this sum should equal IT. Now measure the total circuit current using the method of Lab 2 (break the circuit at point A and insert an ammeter). Comment on your results. Enter these currents in the table. Part D Procedure: 4. Lessons of Lab 3, 4 and Part A of this lab can be applied to more complex series-parallel circuit. The trick is to recognize simple series and parallel parts in the complex. Combination circuit and then apply series circuit rules to the series parts and parallel circuit rules to parallel parts. 5. Enter the values from the Pre-Lab for this circuit in Table 4 on the next page. 6 It 18 R1 1.5kΩ V1 10 V 15 Ir2 A Ir3 R2 R3 3.3kΩ 8.2kΩ Jumper for fault simulation when required 16 17 B R4 1.5kΩ Ir4 = It Fig. 2 Calculated Table 4:Measured Simulated Fault RT IT IR1 IR2 IR3 IR4 VR1 VR2 VR3 VR4 6. Measure the voltage drop on each of the resistors and record in your table. 7. Measure the current into the parallel loop by dividing V1 by R1. Repeat for the current out of the loop (by dividing VR4 by R4). Enter in the table. 8. Measure the branch currents in the parallel branches (IR2, IR3) using the indirect methods. Record in your table. 9. Add up V1, V2 and V4, also V1, V3 and V4. V1 + V2 +V4 = V1+V3+V4 = Comment on your results. 10. Add IR2 and IR3. Compare with IT (or IR1 or IR4). Comment on your results. 11. Introduce a short circuit fault by connecting a jumper between points A and B as shown in the circuit diagram Figure 2. 12. Measure RT, IT, IR1, IR2, IR3, IR4, VR1, VR2, VR3 and VR4 and enter in your results in the table. 13. Based on your simulated fault measurement values, state some basic facts about short circuit faults in series – parallel combination circuits. 7 Questions and Assignments: 1. For E = 10V, R1=10K, R2=18K, R3=22K, Calculate RT, IT, VR1, VR2 and VR3. For a series circuit, draw the circuit diagram. Show current direction and label all voltage drops with proper polarities. Show each step on his calculations. 2. For the circuit shown, there is a break between resistors R2 and R1 as shown. (a) What is the voltage across R2. (b) What is the total circuit current. (c) If the voltmeter is connected as shown, what would the voltmeter read? 9 5 R1 6 R2 V2 25 V 8 V R3 7 3. For E=25V, R1=10K, R2=18K, R3=22K, Calculate RT, IT, I1, I2, I3, VR1, VR2 and VR3 for a parallel circuit. Draw the circuit diagram, show all current directions, label all voltage drops with correct polarities clearly marked. Show each step of your calculations. 4. Why was it not possible to measure the current using the indirect method when measuring the total circuit current in part A, step 3? 8