Page 54 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

Function generator and cathode ray oscilloscope (CRO)

Objectives: At the end of this lesson you shall be able to
• explain the use and control of function and AF (audio frequency) generator
• explain the function of CRO with block diagram
• state the functions of various controls in CRO
• state the use of CRO in electronic circuits.

Introduction: A function generator is an equipment capable of providing sine, square and triangular wave
outputs at different frequencies and amplitude. It has a maximum of 20 volts peak to peak single amplitude. A
function generator finds applications in frequency modulations, tone control, Audio electronic, other laboratory
and research work.
Panel controls and features of function generator

The front panel controls of function generator. (Fig 1)

Fig 1

1 Power ON-OFF switch: To turn on the function generator this button should be depressed. To turn off the
same button should be pressed to release.
2 Range selectors: The range selection is of decade frequency type. The output frequency is given by the
product of range selected and frequency dial indication. For example if the 10 K range button in depressed
and frequency dial is at 2, then the output frequency is 20 KHz.
3 Function selectors: These selectors select the desired output waveform. (square, sine or Triangle)
4 Output jack: The wave forms selected by the function switches are available at this jack.

5 VCO input jack: An external voltage (not exceeding ± 20V peak) input will vary the output frequency. The
change in frequency is directly proportional to the input voltages.
6 TTL JACK: A TTL (Transistor, Transistor logic) square wave is available at this jack. This output is independent
of the Amplitude.
7 Amplitude control: This controls the amplitudes of the output signal.
8 Offset control: This controls the DC offset of the output.

9 Fine frequency dial: The output frequency of the wave forms is given by the product of the setting of this dial
and the range selected.
Operating information: The function generator is powered by 240V. AC mains. When the power ON switch is
depressed the LED will glow.
The desired frequency is set by depressing the frequency range switch an positioning the fine frequency dial.
The desired wave from is selected by depressing the appropriate function button from sine, square or triangle.

The amplitude of the selected output signal is adjusted by Amplitude control knob. A variation of the display
amplitude from 0-20 V peak is possible. The TTL output is not affected by the amplitude control.

41

CITS : Power - Electrician & Wireman - Lesson 60-69