The Oscilloscope

OBJECTIVES

This report aims to:

• Make the student familiar with the construction, components, and fundamental operation of an oscilloscope.

• Know how to set the amplitude and frequency of a function generator.

• Get the knowledge of using an oscilloscope to measure both dc and ac voltage levels.

• Get the knowledge of the impact of the AC/DC/GND switch on the displayed waveform.

BACKGROUND THEORY

In this experiment will be used the DMM, an Oscilloscope, a function generator and a power supply.

·         The DMM read resistance, voltage and current with a digital display.

·         Power supplies gives a source of power, rated as maximum voltage and current output

·          The oscilloscope is an instrument that will display the variation of a voltage with time on a flat screen monitor.

·         The sweep oscillator will make a sawtooth waveform to move the applied signal across the screen.

·         A function generator typically expands on the skills of the audio oscillator by supplying a square wave and triangular waveform with an increased frequency range.

EQUIPMENT

·         Digital Multimeter                  (Brand: Good Will Instruments Co. Ltd, Model: GDM-8135, Serial Number: CF-922334)

·         Oscilloscope                            (Brand: HAMEG, Model: HM 203-6, Serial Number: 46/87 Z33418)

·         Function generator                  (Model: TG 550)

EXPERIMENTAL METHOD AND PROCEDURE

Part 1

The oscilloscope was switched on the ground position and the Y-position to the 0V reference. Then the oscilloscope was switch to the dc position and the vertical sensitivity to the 1V/div. Then it was connected to the 1.5V power supply. The measured was taken. Then the vertical sensitivity was changed to 0.5V/div and the measured was taken (table1.1). Then the voltage was increased to 3V.                                                                                                                                             

                                                                                                                                                                                                              .                                     dc Voltage = (Vertical Shift) x (Vertical Sensitivity)

Part 2

The oscilloscope was connected to the function generation. The frequency of the generation was 500Hz. The vertical sensitivity of the oscilloscope was 1V/div. and the horizontal sensitivity was 0.5ms/div. The oscilloscope was switched on the ground position and the Y-position to the 0V reference. Then it was switch on the dc position. The generation had value of 6V peak to peak swing. The resulting waveform has the following mathematical formulation.     v=Vmsin2πft = 3sin2π500t. Making the necessary adjustments to display the following waveform v=0.2sin2π500t (fig 1) and v=8sin2π500t (fig 2).

Part 3

Making the necessary adjustment placed the following waveform on the oscilloscope. v=0.4sin62, 832t (table 2.1) (fig 3) and v=5sin377t (table 2.2) (fig 3).

Part 4

The oscilloscope was connected in series with 1.5V and the 1sin2π 500t function generator. The oscilloscope was switched to the GND position and the Y-position to the 0V reference. Then it switched on the AC and then switched to DC mode (fig 5).   

OBSERVATIONS

Table 1.1 dc voltage measurement

Table 2.1 v=0.4sin 62.832t

Table 2.2 v=5sin377t

Data discussion

On the table 1.1 seeing that the dc voltage = (vertical Shift)*(vertical sensitivity). When the vertical shift is 1.5 and the vertical sensitivity is 1V the dc voltage is 1.5V and when the vertical shift is 3 and the vertical sensitivity is 0.5V the dc voltage is 1.5v.

On the table 2.1 and 2.2 seeing that v=Vm sinwt, 2πf=w => f=w/2π. The period is equal 1/frequency. w=62.832   f=62.832/2π => f=10KHz and T(period) = 1/10KHZ= 50μs

RECOMMENDATIONS

The oscilloscope is an instrument that will display the variation of a voltage with time on a flat screen monitor.  The signal of interest is applied to the vertical input.  The horizontal input allows applying another signal of any kind to influence with the vertical input to make a wave form that can often be quite informative.

The sweep oscillator will make a sawtooth waveform to more the applied signal across the screen. The waveforms are said to be “in sync” when the frequency of the applied signal and that of the applied signal and that of the sawtooth waveform are the same. If the two frequencies do not match the waveform will appear to be continually moving horizontally.

The applied signal appears across the full width of the screen in a undistorted manner in a straight line with time. The voltage between the two input terminals is increases and decreases in an oscillatory manner for the case of an applied sinusoidal voltage.

In the absence of the sawtooth waveform at the horizontal input the waveform on the screen would simply be a vertical line with a high intensity spot moving up and down on the screen.