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Signals & Measurements

Here are a few places that students have recommended around Manchester
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Cheyenna Thill

on 24 July 2013

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Transcript of Signals & Measurements

Signals & Measurements
Digital Signals
Signal Measurements
Distortion
Frequency Distortion
Test Bench Results
Waveforms
PSpice Simulation
Introduction:
Objectives:
Circuit Equipment:
PSpice Simulation
Test Bench Results
Results Analysis
Results Analysis
PSpice Simulation
Test Bench Results
Results Analysis
PSpice Simulation
Test Bench Results
Results Analysis
Test Bench Results
Test Bench Results
Results Analysis
Utilize standard laboratory equipment
Obtain standard laboratory measurements
Observe system limitations
Generate PSpice Simulations
Analyze the simulation results against the test bench results
Use a signal generator, power supply and oscilloscope effectively
Observe sinewaves, triangles, and squarewaves
Compare digital and oscilloscope measurements
Compare rms and oscilloscope measurements
Measure amplifier characteristics including the gain, input impedance and output impedance
Measure digital characteristics including the rise/fall time, propagation delay and the noise margin
Review voltage division
Observe signal distortion
Four 10K resistors
One 1N4001 diode
One 2.2uF capacitor
Test Bench Equipment:
Signal generator
Digital Multimeter
Oscilloscope
Simulation Software:
PSpice
Diagram Schematic
Sinewave
Trianglewave
Squarewave
Input vs. output using voltage divider Vout = Vin((R1+2)/Rtotal))
Input 10V p2p @ 20KHz
Output 5V p2p @ 20 KHZ
Input 10V p2p @ 20KHz
Output 5V p2p @ 20 KHZ
Input 10V p2p @ 20KHz
Output 5V p2p @ 20 KHZ
Sinewave
Trianglewave
Squarewave
Input 10V p2p @ 20KHz, DVM 3.36V
Output 4.98V p2p @ 20 KHz, DVM 1.97V
Input 10V p2p @ 20KHz, DVM 3.36V
Output 4.99V p2p @ 20 KHz, DVM 1.53V
Input 5.2V p2p @ 20KHz
Output 2.7V p2p @ 20 KHz, DVM 1.5V
Waveshape (Voscope-peak) VDM (Voscope-peak)/VDM
Sinewave
4.98-2.5 = 2.48V 1.97V 2.48/1.97 = 1.26V
Trianglewave
4.99-2.5 = 2.49V 1.53V 2.49/1.53 = 1.63V
Squarewave
5.2-2.7 = 2.5V 1.5V 2.5/1.5 = 1.66V
Ratio Calculations
Explain why the ratio change
For which waveshape is it sqrt(2)
Sinewave input
10V p2p @ 20KHz
Digital Multimeter Output
Reading across lowest 3 resistors
Oscilloscope Output
Reading across lowest resistor
Oscilloscope Output
Reading across second lowest resistor
Diagram Schematics
Expected Results
Using the Voltage Divider Rule it can be seen how the signal is reduced due to the voltage drops across each resistor
Since each resistor has the same value, it can be seen that at each point the voltage drop was approximately 25% less than the voltage at the previous point
Diagram Schematics
Expected Results
Sinewave
Input 10V p2p @ 20KHz
Diode
Output 2.9V p2p @ 20KHz
Half Wave Rectifier
The half wave rectifier is made up of a diode and a resistor
Used to eliminate either the negative or positive alteration of the input signal
The diode direction determines which half-cycle is eliminated
The signal distortion is due to the rectification of the forward biased diode
Comparing to the PSpice simulation, the waveforms are coincident for the first part of the signal.
The time difference and the phase shift of the output is due to propagation delay.
When the diode points toward the load, the output from the rectifier will be positive
When the diode points towards the transformer, the output from the rectifier will be negative
Sinusoidal input voltage
Rectified output voltage
Diode voltage
Input 10V p2p @ 20KHz
Sinewave
Output 1.6V
Trianglewave
Input 10V p2p @ 20KHz
Output 1.6V
Squarewave
Input 10V p2p @ 20KHz
Output 2.4V
Sinewave
Trianglewave
Squarewave
Input 10V p2p @ 20KHz
Output 3.1V p2p
Input 10V p2p @ 20KHz
Output 2.54 p2p
Input 10V p2p @ 20KHz
Output 4.24V p2p @ 20KHz
Analysis
How do the digital and oscilloscope measurements compare for different waveshapes? Why?
What occurs when you connect the two ground probes of the oscilloscope together?
How does the diode affect the signal? How does the capacitor affect the signal?
How do the measured results compare to the PSpice results?
Oscilloscope Overview
Red Calibrate Knob
VERT MODE
DC vs. AC
X*Y on the time selector
Conclusion
For what signal is Vpeak = sqrt(2)*Vrms?
What happens when you add a new ground to the circuit?
What is distortion? What signal is not distorted by the RC circuit?
Describe what was demonstrated about signals in the laboratory.
Explain of how KVL is important and the differences between using different measuring tools.
What type of measurement gives you the most accurate measurement of signals?
What is distortion?

As the signal propagates through the circuit from the input to the output, there is an undesired change in the signal waveform.
This distortion can either be in the form of amplitude, frequency or phase distortion depending on the circuit.
1.75V Output at 0.707 of the original output
100Hz
f3db=6.46KHz
f3db/10=646Hz input
2.5V output sinewave
Output
5V Digital Pulse 0 to 5V
2.4V output
5V Digital Pulse 0 to 5V
5V Digital Pulse 0 to 5V
2.4V Output
0.6V Output
6.46KHz
6.46KHz
64.6KHz
64.6KHz
Using this method to obtain the f3db was not intuitive
There was distortion with frequency change
Full transcript