Lissajous method

lissajous-method

1. LISSAJOUS METHOD FOR FREQUENCY AND PHASE MEASUREMENT Dr. R. M. Thombare HOD. Dept. of Physics M. G. College Armori

2. Measurement of Frequency by Lissajous method The Oscilloscope is a Sensitive indicator for Frequency and Phase Measurements. The Lissajous Pattern Results ,when sine waves are applied simultaneously to both pairs of deflection plates. If One frequency is an integral multiple of other ,the pattern will be stationary and is called a Lissajous figure.

3. Measurement of Frequency by Lissajous method The Resulting Patterns depend on the integral and phase relationship between two frequencies.

4. Measurement of Frequency by Lissajous method Measurement Procedure Set up the Oscilloscope and Switch off the Internal sweep(Change to Ext) Switch off Sync. Control Connect the Signal sources as shown in above fig. Set the Horizontal and Vertical gain Control for desired width and height of the Pattern Keep freq f v Constant and Vary freq f h noting that the pattern spins in alternate directions and changes shape. The Pattern stands still when ever f v and f h are in an integral ratio(either even or odd) When f v = f h , the pattern stand still and is a single circle or ellipse When f v =2f h ,a two loop horizontal pattern is obtained.

5. Measurement of Frequency by Lissajous method

6. Measurement of Frequency by Lissajous method

7. Measurement of Phase by Lissajous method Procedure Set up the Oscilloscope and Switch off the Internal sweep(Change to Ext) Switch off Sync. Control Connect the Signal sources as shown in below fig. Set the Horizontal and Vertical gain Control for desired width and height of the Pattern

8. Cont … . 5. Keep f V constant and vary frequency f h noting that the pattern spins in alternate directions and changes shape. 6. When two frequencies are equal and in phase, The pattern appears as a straight line at an angle of 45 with horizontal. 7. As the Phase between the two alternating signal changes, the pattern changes cyclically as shown in below fig.

9. Cont ….