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

2. 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

3. 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

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

5. 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

6. Oscilloscope 6 From Function Generator Power The oscilloscope displays input signal as voltage vs. time. Voltage time (You don’t have these inputs.)

7. 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

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

9. 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] * For this course, we recommend that you set your signal generator to be driving a high impedance (resistance in this case) load.

10. 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

11. 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 , or you set it to “High Z Load”. 0

12. The “T” Connector 12 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

13. Coupling 13 Whether or not you observe the dc component on the scope depends on the coupling. 2. Select whichever channel your signal is connected to. 3. Toggle through the coupling options: dc: dc AND ac components are displayed. ac: only the ac component is displayed. 1. Generate a signal with a dc offset, and connect it to the oscilloscope. The dc coupling option is named badly. It should be called something like, “everything”.

14. 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

15. Triggering 15 When the oscilloscope is properly triggered, the image is “stable” because it is displayed the same way each time it sweeps across the screen. By “the same way”, we mean that it starts at the same point every time. If the triggering is not correct, the image looks garbled, like it is “running” across the screen. Try adjusting the trigger level, and see what happens. Trigger Menu Trigger Level

16. External Triggering 16 An external trigger signal is provided by the SYNC output of the function generator. This provides a square wave of about 3[Vpp] amplitude at the frequency of the Output waveform, and synchronized with it. So as long as your signal is coming from the Output of the signal generator, the scope knows exactly when to trigger! The external trigger input of the oscilloscope is on the back, at the top.

17. Fun With Speakers! 17 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)?