Lab 8 Induction to Oscilloscope The objective of this Lab is to become familiar with alternating voltages and currents and the operation of the oscilloscope. Equipment: Oscilloscope (it plays a role as multimeter in a DC circuit) Function Generator/AC source (it plays a role as a DC source/battery in a DC circuit) Coaxial cable

Theory The potential difference (voltage), and current in AC circuits are very with time. The simplest time-varying voltage or current varies periodically between positive and negative values with fixed maximum and minimum values. The magnitude of the maxim and minim is called the amplitude and is given in volt (V), millivolt (mV), etc. The time is takes the function to repeat itself is called the period, and is given in seconds (s), milliseconds (ms), etc. The reciprocal of the period is the frequency, which is the number of cycles per second. The frequency is denoted by the letter f and the unit is hertz (Hz). Oscilloscope is probably the most versatile measuring instrument in electronics to study time dependent voltages. With it, it is possible to obtain a dynamic graph of the variation of a voltage or current versus time. The oscilloscope is a cathode ray tube in which the electrons are accelerated and deflected by two sets (X and Y) deflect plates. For example, a sinusoidal input voltage across the vertical (Y) plate will cause the beam to move up and down sinusoidally. At the same time the electron beam is sweeping simultaneously, in the horizontal plane (X). The crucial step in obtaining a repetitive wave form on the screen for a time-varying input signal is to have the horizontal sweep time synchronized with the input signal. When a repetitive wave display has obtained, one can read the horizontal time from the front panel of oscilloscope to determine the period or frequency of the input signal. The amplitude of the wave is controlled by the vertical input voltage and is also readable from the front panel of the oscilloscope.

Vertical displays (amplitude of voltage) Procedures Connect the oscilloscope’s Channel 1 input to the output of the function generator. Produce a square wave at 1000 Hz and observe with the oscilloscope. Select appropriate settings for both the horizontal sweep time (sec/div) and the vertical amplification (volts/div) so that a complete cycle of the square wave occupies most of the display space. The X and Y unit length on the grade sheet of oscilloscope’s screen is defined as division (div). Vertical displays (amplitude of voltage) Check the vertical dial’s position of the front panel of oscilloscope, for example, if it is on 0.1 volts/div, that means 0.1 vilts per vertical division. Amplitude Dial Position ___________________(volts/div) Count the number of vertical divisions between the peak to peak on the screen and multiply it by the value of volts/div read from A. # of Division (Peak-Peak) ____________________ Check the setting on the input cable of oscilloscope to see if it is on “1X” or “10X” or other “valueX”. Multiply the measured value from C by that value (for example, multiply 10 if it is on the “10X” position). Record the measured voltage by the oscilloscope. Measured Voltage _____________________ Horizontal time scale Record the frequency either from the digital display or numerical setting (depends on different generator you are using). Calculate and record the period which is the reciprocal of the frequency. Period of Input Signal __________________ Check the horizontal dial’s position of the front panel of oscilloscope, for example, if it is on 0.1 sec/div, that means 0.1 second per horizontal division. Time Dial Position ___________________(sec/div) Count the number of horizontal divisions within a complete wave on the screen and multiply it by the value of sec/div read from B. This is the measured period. Measured Period ____________________ Compare the measured values of period of C with A and calculate the respective error percentage.

Oscilloscope Signal Generator Repeat the above procedures outlined in 2 for a sine wave. Repeat the above procedures outlined in 2 for a sawtooth wave. Oscilloscope Signal Generator Use Signal Generator (output) as the signal source of Oscilloscope (input), Red-Red, Blk – Blk BLK of SG and BLK of Osci. always connect together– ground

How to read Voltage --- Time graph Count the number of division Voltage --- Y axis --- Vm – 2.0 div Time --- X axis --- T (period) – 4 div Y (volts): Vm = 2.0 div x 1 volts/div = 2.0 volts X (time): T (period) = 4 div x 0.2 sec/div = 0.8 s 1 volt/div 0.2 sec/div

Using Oscilloscope and Function Generator to repeat Lab 7 𝑅 C Function Generator 𝑅 Oscilloscope R=100, C=100µ (in the circuit box) 850 Universal Interface Signal/Function Generator Setup Waveform: Positive squire wave Frequency: (Signal Period = 10 τ) Amplitude 1V Coaxial cable connect from circuit to Oscilloscope: one side connect to Oscilloscope, the other side (should have two wires: Red and Blk) connect to the above circuit. Coaxial cable connect from circuit to Signal/Function Generator: one side connect to the Function Generator, the other side (should have two wires: Red and Blk) connect to the above circuit. Signal/Function Generator and Oscilloscope should have the same electric potential (ground), black color (Blk).