Experiment 1: Error & Statistical Measurements.

Transcription

1 P band P band P band Experiment 1: Error & Statistical Measurements. Objectives: 1T1. To identify resistors values and tolerances from the color code and measurement.1t 1T2. To learn how to use the ohmmeter to measure resistance.1t 1T3. To compare the color coded resistor tolerance with the actual measured resistance value. Equipments and Components: 1 1kΩ. 5- Unknown Resistors. 1-1-Voltmeter. 1-Ammeter. DC Power Supply. Student Lab Kit. Background: The0T 0Telectronic color code0t 0Tis used to indicate the values or ratings of electronic components. Color code system is very common for0t 0T 2Tresistors2T. Color bands are commonly used because they are easily printed on tiny components. Each resistor has three or more colored bands; three bands colored resistor is shown in figure 1. Each band has only one color, and each color has a specific value as shown in Table 1. To read the color of any three band resistor follow the following method: 1P 2P 3P st nd rd is the first significant value (left side). is the second significant value. is the decimal multiplier. 1

2 P The last color is used for tolerance (if founded), if there is no color, coriander it as 20%. To identify the tolerance band easily, there is a gap between it and the third band. Resistors are never to be the exact value that the color codes indicate. Therefore, manufacturers place tolerance color on the resistor to tell you how accurate this resistor made. It is simply a measurement of the imperfections. Fig.1: 3 Bands Colored Resistor. Table 1: Color Coding System. Now let us read the resistance value of the resistor shown in figure 1. The first band is red which equal to 2, the second band is violet and equal to 7, the third band is green and called Multiplier which represent the number of zeros green 5 =5. The tolerance is gold, which equals +\- 5%. The resistor value is 27*10P = Ω, +\-5%. 2

3 UProcedure: UPart 1: Determining Resistance value using colors code": You will be provided with 5 unknown resistors, use colors code system to specify their values, then record these values in table 3 and 2, then calculate the higher and lower values. UPart 2 : Determining Resistance values using Ohmmeter: 1-Install the first unknown resistor in the student lab kit. 2- Connect the ohmmeter around the resistor terminals and measure the resistance. 3-Record the measured values in the table Repeat steps 1,2 and 3 for others four unknown resistors. UPart 3: Determining Resistance values using simple Electric Circuit: 1- Build the circuit shown in figure 2. Fig. 2: Simple Electronic Circuit. 2- Put the first unknown resistor as mentioned in figure Set the DC power supply to 10 v. 4- Using Voltmeter and Ammeter measure the voltage across the unknown resistor and the current that flow through it. 5- Calculate the resistor value using this equation R = V I. 3

4 6- Record the calculated resistance in table 4 and Repeat steps 1, 2, 3, 4, 5 and 6 for others four unknown resistors. Part 4: Calculations: 1- From parts 2 and 3, calculate the arithmetic mean for the five unknown resistors using this equation X = X1+X2+Xn. n 2- Calculate the Error for the five unknown resistors using: Error (%) = Rm Rc Rc Record your calculations in table 2. Part 5: Questions to be answered 1- Compare the error percentage to the tolerance for each unknown resistor, if the error percentage is within the range of tolerance; write (Yes) in the note column of table 2. On the other hand, if the error percentage is out of range of the tolerance, write (No) in the note column. 2-Discuss the sources of errors! 4

5 1P 2P 3P 4P Data Sheet Table 2: Results Table. Color Value Higher Value Lower Value Measured Value- Ohmmeter Measured Value- Circuit Mean ا Note Error (%) Table 3: Results Table. st P Band nd P Band rd P Band th P Band Tolerance Resistance Value (Ω) color value color value color value color value color value

6 Table 4: Results Table. V (V) I (A) R (Ω) =V\I

7 Experiment 2: Voltmeter Ammeter Method of DC Resistance Measurement. Objective: The purpose of this experiment is to demonstrate how to measure a fixed DC resistance using simultaneous measurements of voltage and current. Because meters have their own internal resistance, they affect the circuit resistance, weather in series or parallel. Depending on the nature of the load, two methods are possible, namely method A and B where are shown in figure 1 and 2 respectively. Equipments and Components: 2-1kΩ Ω Ω. 1-Voltmeter. 1-Ammeter. DC Power Supply. Student Lab Kit. Procedure: Part 1: Measuring Resistance Value using Ohmmeter: 1-You will be given a three resistors as listed in table 1. Measure their values using ohmmeter, then write down your results in the table Calculate the error percentage between the listed resistors values and measured values in table 1. 7

8 Part 2: Measuring Resistance Values using simple Electric Circuits: A- Using Method A: 1- Build the circuit shown in figure Install the first resistor in the circuit. 3-Adjust the DC power supply between 0 and 10 v, so that the ammeter reads an exact value, such as 0.5 ma. 4- Accurately measure the voltage across the resistor, record this reading and Ammeter reading in table Using Ohm's law R = V, calculate the resistance value and record it in table1. I 6- Calculate the error percentage between the listed resistors values and measured values in table Repeat steps 1, 2,,4,5 and 6 for the two remaining resistors listed in table 1. Figure 1: First method of measurement. 8

9 B- Using Method B: 1- Build the circuit shown in figure Install the first resistor in the circuit. 3-Adjust the DC power supply between 0 and 10 v, so that the ammeter reads an exact value, such as 0.5 ma. 4- Accurately measure the voltage across the resistor, record this reading and Ammeter reading in table Using Ohm's law R = V, calculate the resistance value and record it in table1. I 6- Calculate the error percentage between the listed resistors values and measured values in table Repeat steps 1, 2,,4,5 and 6 for the two remaining resistors listed in table 1. Figure 2: Second method of measurement. Part 3: Comments and Conclusion: Write your comments and conclusion about the three different errors mentioned in part 1, part 2 (A) and part 2 (B) and discuss the sources of errors. 9

10 Data Sheet. Table 1: Results table Method A Method B Vale Measured (Ohmmeter) Error% Volt (V) Current (A) Resistance (Ω) Error% Volt (V) Current (A) Resistance (Ω) Error% 1000Ω 470Ω 100Ω 10

11 Experiment 3: Measuring the Internal Resistance of a DC Power Supply. Objective: 1- Measuring the internal resistance of a DC power supply. 2- Study the effect of the internal resistance of a dc power supply on an electric circuit. Equipments and Components: 2-1kΩ. 1- Variable Resistor 1-Voltmeter. 1-Ammeter. DC Power Supply. Student Lab Kit. Background: All sources of e.m.f. (Electromotive Force: 1TCapable of accelerating electric charges and creating electric current, having electric potential) behave as they have 1Tresistance connected in series with them as shown in figure 1. This resistance is called the internal resistance, it is resistance to the flow of current inside the power supply itself. Fig 1: Power supply internal resistance equivalent circuit. 11

12 The internal resistance is a part of the total resistance in the circuit. It behaves like any other resistance in the circuit. It needs a voltage across it to push current throw it. Unfortunately, it is not possible to measure the internal resistance directly. As current flows through the source, there is a voltage drop across the internal resistance. This voltage drop is the lost volts when current is drawn from the source. Procedure: Part 1: Measuring the Internal Resistance of a DC Power Supply: 1-Build the circuit shown in figure Set the DC power supply to 15 v. 3-Change the variable resistor till you reach 7.5 v (half value of the DC power supply voltage) across the variable resistor. 4-Measure the current flown in the circuit using an Ammeter, and record it in table 1. 4-Calculate the internal resistance using the following equation: V = I R internal + I R, and put your answer in table 1. Fig.2: Measuring the internal resistance of a dc power supply. 12

13 Part 2 : Study the effect of the internal resistance on an Electric Circuit: 1- Build the circuit shown in figure 3. 2-Set the DC power supply to 15 v. 3-Use an Ammeter to measure the flown current in the circuit, then put it in table 1. 4-Consider the new value of the resistor in the circuit: RRnewR = R - RRnternalR. 5-Calculate the new value of current based on new value of the resistor R, I new = V Rnew and record your result in table 1. 6-Calculate the error between the measured current in step 3 and calculated current in step 5 using this equation = ( I calculated I measured I calculated )*100. Fig 3. 13

14 Data Sheet Table 1: Result table. Part 1 Part 2 I RRinternal I RRnew IRnew Error 14

15 Experiment 4: Measuring the Internal Resistance of a Voltmeter and an Ammeter. Objective: 1- Measuring the internal resistance of a Voltmeter and an Ammeter. 2- Study the effect of the internal resistance of a Voltmeter and an Ammeter. on an electric circuit. 3- Calculate errors that produced by installing the Voltmeter or Ammeter in an electric circuit. Equipments and Components: Ω Resistor. 1-1 M Ω Resistor. 1-Voltmeter. 1-Ammeter. DC Power Supply. Student Lab Kit. Procedure: Part 1: Measuring the Internal Resistance of an Ammeter: 1-Build the circuit shown in figure 1. Figure 1: Part 1 circuit diagram. 15

16 2-Set the DC power supply to 5 v. 3-Measure the voltage across the DC power supply terminals V measured, the resistance value of the resistor (100Ω) R measured and the flown current in the circuit I measured, record your readings in table 1. 4-Calculate the flown current in the circuit using I calculated = V measured R measured, record your answer in table 1. 5-Calculate the internal resistance, I measured = table 1. V measured (R measured +R A), record your answer in 6-Calculated the error, Error = ( I calculated I measured ) 100, record your answer in I calculated table 1. Part 2: Measuring the Internal Resistance of a Voltmeter: 1-Build the circuit shown in figure 2. 2-Set the DC power supply to 5 v. Figure 2: Part 2 circuit diagram. 3-Measure the voltage across the DC power supply terminals V measured, the resistance value of the resistor (1MΩ) R measured and the flown current in Voltmeter IRvR, record your readings in table 2. 5-Calculate internal resistance, R V = V measured I v, record your answer in table 2. 6-Calculate R total, R total = R measured R V R measured +R V. 7-Calculated the error, Error = ( R measured R total R measured ) 100, record your answer in table 2. 16

17 Data Sheet Table 1: Part 1 result table. Part 1 V measured (V) R measured I measured (A) I calculated (A) R A Error(%) Table 2: Part 2 result table. Part 2 V measured (V) R measured IRvR(A) R V Error(%) 17

18 Experiment 5: Function Generator. A) Op-Amp (Integrator): 1-Build the circuit shown in figure 1. 2-Fill out table 1. Fig.1. Table1. Input Signal Sine wave Triangle Wave Square Wave Output Signal 18

19 A) Op-Amp (Differentiator): 1-Build the circuit shown in figure 2. 2-Fill out table 2. Fig.2. Table 2. Input Signal Sine wave Triangle Wave Square Wave Output Signal 19