I. Experimental Purpose \ x0d \ x0d \ 1. Understand the working principle of double trace oscilloscope display waveform; \x0d\\x0d\2。 Learn to observe voltage signal with double trace oscilloscope; \x0d\\x0d\3。 Learn to observe Lissajous figure with double trace oscilloscope, and use it to measure the frequency of sinusoidal signal. \x0d\\x0d\ II。 Experimental instruments \ x0d \ x0d \ signal generator, double-trace oscilloscope and probe. \x0d\\x0d\ III。 Experimental principle \ x0d \ x0d \ 1. Oscilloscope \ x0d \ 2. Principle of double trace oscilloscope \ x0d \ x0d \ 3. Principle of oscilloscope display waveform \ x0d \ x0d. When the change period of sawtooth voltage is equal to the change period of sinusoidal voltage, a full-cycle sine wave will be displayed, as shown in Figure 3. If the sine wave is added to YCH 1 and YCH2 at the same time, and the sawtooth wave inside the oscilloscope is added to the X deflection plate of the oscilloscope, two sine waves will be obtained on the screen. \x0d\\x0d\4。 The basic principle of Lissajous graph \ x0d \ x0d \ When sine waves are applied to the Y deflection plate and the X deflection plate of the oscilloscope respectively, Lissajous graph can be obtained when the frequency ratio of signals is a simple integer ratio. Fx and fy are the signal frequencies on the deflection plates of X and Y, and nx and ny are the number of tangents between Lissajous figure and imaginary horizontal and vertical lines. \x0d\\x0d\ IV。 Experimental content \ x0d \ x0d \ 1. Get ready and set up an oscilloscope; \x0d\\x0d\2。 Observe various waveforms; \x0d\\x0d\3。 Measure the peak voltage, period and frequency of sine wave, and measure four sets of data. \x0d\\x0d\ VI。 Thinking about the problem \ x0d \ x0d \ 1. The principle of oscilloscope displaying voltage-time diagram (that is, electric signal waveform) is briefly described. \x0d\\x0d\ A: When high-speed electrons collide with the fluorescent screen, the fluorescent substance will emit light, and a bright spot can be seen on the fluorescent screen. The Y deflection plate is two electrodes placed horizontally, and the X deflection plate is two electrodes placed vertically. When the voltage is applied to the Y deflection plate and the X deflection plate respectively, the corresponding patterns can be obtained on the fluorescent screen. Of course, different voltages and different periods will produce different patterns. \ x0d \ v. Data processing and analysis \x0d\ 1. The peak voltage of the measured sine wave \x0d\ is multiplied by the measured value of Vp-p (v), the true value of VP-P (v) and the error (v) \ x0d \13.6840.32 \ 313.315/kloc-0. Measure the period, frequency \ x0d \ times of sine wave, and the true value of t (S)f true value (HZ)f measured value. 11×10-21001000 \ x0d \ 21×10-4104/. 90 12 180 180. 1 \ x0d \ 902 14545.2 \ x0d \ 90326060.7 \ x0d \ VI。 Question \ x0d \ x0d \ \x0d\\x0d\ A: High-speed electrons hitting the fluorescent screen will make the fluorescent substance glow, and a bright spot can be seen on the fluorescent screen. The Y deflection plate is two electrodes placed horizontally, and the X deflection plate is two electrodes placed vertically. When the voltage is applied to the Y deflection plate and the X deflection plate respectively, the corresponding patterns can be obtained on the fluorescent screen. Of course, different voltages and different periods will produce different patterns. \x0d\ VII。 Precautions \ x0d \ x0d \ 1. The brightness of the light spot (scanning line) on the fluorescent screen should not be too bright, and the light spot (or bright line) should not be fixed at a certain point on the fluorescent screen for too long to avoid damaging the fluorescent screen. \x0d\\x0d\2。 All switches and knobs on oscilloscopes and function signal generators have certain adjustment limits, so don't use too much force when adjusting. \x0d\\x0d\3。 The two input terminals CH 1 and CH2 of the dual trace oscilloscope have a positive * * grounding terminal. When CH 1 and CH2 are used at the same time, short circuit of external circuit should be prevented.