the function generator and the oscilloscope dr. len trombetta 1 ece 2100
TRANSCRIPT
The Function Generator and the Oscilloscope
Dr. Len Trombetta
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ECE 2100
Sinusoid Basics
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General form of the sinusoid:
v(t) = Vm sin(2pf t + f) [V]
• Vm is the amplitude• f is the frequency• f is the phase• 2Vm = Vpp (peak-to-peak)
t
We usually write w = 2pf, and w is the angular frequency. But note that what you set on the function generator is f, not w.
v(t)
Vm Vpp
Sinusoid Basics
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A sinusoid may also have a dc offset.
v(t) = Vm sin(2pf t) [V] + Vdc
v(t)
tVdc0
Function Generator
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Power
Let’s explore basic function generator properties...
Displays and Output
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The default setting is1 [kHz], displayed here…
…and 100 [mV] peak-peak amplitude, displayed by pressing this button.
Next, connect Output to the oscilloscope using a BNC-to-BNC cable.
scope
You won’t get an output until you press “Output”.
BNC to BNC
Oscilloscope
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From Function GeneratorPower
The oscilloscope displays input signal as voltage vs. time.V
olta
ge
time
(You don’t have these inputs.)
Scale Factors
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Vertical scale factor (in Volts/Div)
Horizontal scale factor (in sec/Div)
Convince yourself that the signal frequency and amplitude are what is stated on the function generator display.
Change the scale factors to see how the display is changed on the ‘scope.
f = 1/T T
20 mV/ 500 uS/
Vpp
scale factor adjustments
Waveform (Function)
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Step through the functions to observe each one.
A ramp with a 50% asmmetry is a triangle wave…
Amplitude
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Use the keypad and the Vpp* button…
…or…
…the wheel and the “ten’s place” buttons.
To adjust the amplitude:v(t)
Vm
t
v(t) = Vm sin(2pf t) [V]
* Note that this button generally sets the “0 – peak” amplitude, not the “peak-peak” amplitude. It selects “peak-peak” only if the load is 50 W.
Frequency
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Use the keypad and the Hz, kHz, or MHz button…
…or…
…the wheel and the “ten’s place” buttons.
To adjust the frequency:v(t)
t
T
v(t) = Vm sin(2pf t) [V]
T = 1/f
dc Offset
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Use the keypad and the Vpp* button…
…or…
…the wheel and the “ten’s place” buttons.
To adjust the offset:v(t)
t
v(t) = Vm sin(2pf t) [V] + Vdc
Vdc
* This procedure will give you twice the offset you key in, unless the load is 50 W.
0
Coupling
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Whether or not you observe the dc component on the scope depends on the coupling.
1. Select whichever channel your signal is connected to.
2. Toggle through the coupling options:
dc: dc AND ac components are displayed.
ac: only the ac component is displayed.
The “T” Connector
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output connected to BNC “T”
The three BNC connectors are in parallel, effectively providing two FGEN outputs. Typically one will go to the scope and the other will be your circuit input.
scopecircuit input
RMS Measurements
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Another way to characterize the amplitude of a periodic waveform is the rms (root-mean-square) amplitude:
When set to measure ac voltage or current, the Agilent automatically displays rms.
0
0
21( ) .
t T
rms tV v t dt
T
If v(t) is a sine or cosine (sinusoid), then
.2m
rms
VV
Fun With Speakers!
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Play with the speakers by connecting one output to the speaker and one to the ‘scope. Observe the effects of amplitude and frequency.
speaker
oscilloscopeWhat happens to the sound if you change the wave-form (sine/triangle/square)?
Triggering
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When the oscilloscope is properly triggered, the image is “stable” because it is displayed the same way each time it sweeps across the screen. If the triggering is not correct, the image looks garbled , like it is “running” across the screen.
Trigger Menu
Trigger Level
External Trigger connection
For more info: www.egr.uh.edu/courses/ece/ece2100/Trigger_Controls.pdf
External Triggering
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An external trigger signal is provided by the SYNC output of the function generator. This provides a square wave of 1Vpp amplitude at the frequency of the MAIN waveform. So as long as your signal is coming from MAIN, the scope knows exactly when to trigger!