Page 59 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

Example : Assume a vertical deflection of 6.4 divisions as in Fig 8 and a volt/div setting of 5 volts.
Peak-to-peak voltage = 6.4 x 5 = 32 V
therefore peak voltage = 16 V
therefore RMs voltage = 16 x 0.707 = 11.31 V

Fig 8

DC voltage measurement : The input selector switch is set to DC position. Adjust the Y shift position to get the
trace at the centre of the screen. This line represents zero DC volts. Connect the +ve of the DC voltage to be
measured to input terminal and the -ve to the common terminal. Now the horizontal line will move up. (Down for
reverse polarity) the volts/div switch is set as required.
Now measure the vertical distance in divisions form the zero reference line.
The DC voltage can be found by multiplying the vertical distance (division) with VOLT/DIV setting.

An example is worked out with reference to Fig 9

Fig 9

Assume a vertical deflection of 2.6 division and a Volts/Div setting of 20 V.
DC voltage = 2.6 x 20 = 52V.
Measurement of time and frequency: The wave-form to be measured is connected to the V input. The volts/
Div switch is set to display a suitable vertical amplitude of the wave-form. The Time/Div switch is set to display
approximately two cycles of the wave-form to be measured. Adjust the Y-SHIFT control to move the trace so that
the measurement points are on the horizontal centre line. The X-SHIFT control is adjusted to move the start of
the measurement points to a convenient reference line.
The distance (divisions) between the points of one cycle is measured as in Fig 10.
The product of the divisions of one cycle and the setting of time/div switch gives the period of one cycle.

46

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