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Homework answers / question archive / OBJECTIVES After performing this experiment, students should be able to: 1
OBJECTIVES
After performing this experiment, students should be able to:
1. Demonstrate how a potentiometer varies resistance
2. Construct a potentiometric circuit
3. Conduct an experiment to determine the effect of meter loading on a potentiometric circuit
EQUIPMENT AND MATERIAL LIST
1. Power supply
2. Multi meter
3. Resistors
4. Potentiometer
5. Jumper wires
*Simulation based components
PROCEDURE
1. Set the power supply to 5V. Use this input voltage for the potentiometric circuit in Figure 1 and Figure 2. This must be held constant throughout the experiment.
2. Construct the circuit according to Figure 1
3. Shift the position on the potentiometer scale until the voltage reaches zero.
4. Increase the potentiometer resistance at fixed increments of 10%.
5. Note the potentiometric circuit output voltage (to the nearest millivolt).
6. Repeat steps 4 and 5 for every 10% on the potentiometer linear input scale until 100%.
7. Repeat steps 4-6 for the same 10 readings as the percentage 1s decreased from 100% down to 0%.
8. Analyze the linearity, repeatability and hysteresis of your potentiometer based on your results.
9. Add a 10K resistor between the wiper (output voltage) and ground. This simulates a load on the sensor. See Figure 2.
10. Tabulate the data using the same method as in steps 1-7.
Voltage In
10K Pot. V
Ground
Figure 1
Voltage In
10K Pot. Voltage Out
10K Load
Ground
Figure 2
KEYPOINTS
Include a plot of voltage versus percentage for your potentiometer. Compute the percent linearity, repeatability, and hysteresis. Comment on your choice of a linear range. Comment on the potentiometer resolution. Discuss meter loading effect. Discuss your findings and its correlation to the theory.
Results
Table 1: Potentiometer voltage for 0% to 100%.
Percentage of input (%) |
Voltage (V) |
0 |
|
10 |
|
20 |
|
30 |
|
40 |
|
50 |
|
60 |
|
70 |
|
80 |
|
90 |
|
100 |
|
Table 2: Potentiometer voltage for 100% to 0%.
Percentage of input (%) |
Voltage (V) |
100 |
|
90 |
|
80 |
|
70 |
|
60 |
|
50 |
|
40 |
|
30 |
|
20 |
|
10 |
|
0 |
|
Table 3: Potentiometer voltage for 0% to 100% (with loading)
Percentage of input (%) |
Voltage(V) |
0 |
|
10 |
|
20 |
|
30 |
|
40 |
|
50 |
|
60 |
|
70 |
|
80 |
|
90 |
|
100 |
|
Table 4: Potentiometer voltage for 100% to 0% (with loading)
Percentage of input (%) |
Voltage(V) |
100 |
|
90 |
|
80 |
|
70 |
|
60 |
|
50 |
|
40 |
|
30 |
|
20 |
|
10 |
|
0 |
|