The Function Generator and the Oscilloscope Dr. Len Trombetta 1 ECE 2100

Sinusoid Basics 2 General form of the sinusoid: v(t) = V m sin(2  f t +  ) [V] V m is the amplitude f is the frequency  is the phase 2V m = V pp (peak-to-peak) t We usually write  = 2  f, and  is the angular frequency. But note that what you set on the function generator is f, not . v(t) VmVm V pp

Sinusoid Basics 3 A sinusoid may also have a dc offset. v(t) = V m sin(2  f t) [V] + V dc v(t) t V dc 0

Function Generator 4 Power Let’s explore basic function generator properties...

Displays and Output 5 The default setting is 1 [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 6 From Function Generator Power The oscilloscope displays input signal as voltage vs. time. Voltage time (You don’t have these inputs.)

Scale Factors 7 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/ V pp scale factor adjustments

Waveform (Function) 8 Step through the functions to observe each one. A ramp with a 50% asmmetry is a triangle wave…

Amplitude 9 Use the keypad and the Vpp * button… …or… …the wheel and the “ten’s place” buttons. To adjust the amplitude: v(t) VmVm t v(t) = V m sin(2  f 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 .

Frequency 10 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) = V m sin(2  f t) [V] T = 1/f

dc Offset 11 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) = V m sin(2  f t) [V] + V dc V dc * This procedure will give you twice the offset you key in, unless the load is 50 . 0

Coupling 12 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 13 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. scope circuit input

RMS Measurements 14 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. If v(t) is a sine or cosine (sinusoid), then

Fun With Speakers! 15 Play with the speakers by connecting one output to the speaker and one to the ‘scope. Observe the effects of amplitude and frequency. speaker oscilloscope What happens to the sound if you change the wave-form (sine/triangle/square)?

Triggering 16 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:

External Triggering 17 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!