Use of cro for frequency measurement, Electrical Engineering

Q. Explain the use of CRO for frequency measurement.

 

Measurement of frequency: The frequency of the periodic signals is easily measured with a CRO. The frequency of a signal to be measured is compared with a known frequency. A sinusoidal voltage of unknown frequency (the frequency which is to be measured) is applied to the vertical plates. If the ratio of two frequencies (f and f) is an integer, a clearly defined and distinctive pattern appears on the screen. These patterns are known as Lissajous pattern.

Let us assume that two sinusoidal voltages applied to the vertical and horizontal plates of the CRO have equal frequency and same phase and let that voltages applied to the plates be given as voltage at vertical plate.

When the frequency of the two voltages is not equal then to obtain the Lissajous pattern is not simple. Lissajous pattern may be classified into two general categories, the closed and the open Lissajous patterns. A closed Lissajous pattern is continuous and has no break it has no free ends as shown in fig. The open patterns are simply steady traces and have free ends. 

The ratio of vertical to horizontal frequencies of closed Lissajous patterns can be obtained by counting the number of positive vertical peaks and dividing it by number of positive horizontal peaks and is given by the formulae.

Lissajous patterns are used for accurate measurement of frequency of a waveform. The signal or the waveform, whose frequency is to be measured, is applied to the vertical deflection plates the CRO, an accurately calibrated standard frequency source is used to supply voltage to the horizontal deflection plate with the internal sweep generator switched off.

 

Posted Date: 7/12/2012 6:22:22 AM | Location : United States







Related Discussions:- Use of cro for frequency measurement, Assignment Help, Ask Question on Use of cro for frequency measurement, Get Answer, Expert's Help, Use of cro for frequency measurement Discussions

Write discussion on Use of cro for frequency measurement
Your posts are moderated
Related Questions
Consider the network shown in Figure (a). (a) Find the voltage drops across the resistors and mark them with their polarities on the circuit diagram. (b) Check whether the KV

Working of Hartley oscillator : When the collector supply voltage Vcc is switched on, the capictor gets charged. The capacitor discharges through the inductor, setting up oscil

Explain In brief about the Robots - Robot is programmed with a series of instructions that enable it to carry out a series of tasks - On the other hand, an operator manually

what is the time of short circuit ?

Question: (a) The conversion of a time varying analog audio signal into digital form is carried out using an electronic circuit known as a (signal) encoder. Draw a labeled bl

What is expanded memory system? EMS: The area at location C8000H-DFFFFFH is frequently open or free. Such area is used for the expanded memory system into a XT or PC system, or

The site 450 kVA load is actually a three-phase, six pulse thyristor rectifier feeding a dc bus. Assuming that the voltage waveform at the site 11 kV bus is purely sinusoidal, calc

A 3-phase, 16-pole synchronous machine is driven by a prime mover at a speed of 600-rpm with the stator open circuited. The rotor flux per pole is 0.025-Wb. Determine (a) the fr

Name the 6 modes of operations of an 8253 programmable interval timer. Mode 0: interrupt on terminal count Mode 1: hardware re -triggerable one-shot Mode 2: rate generato