|The controls on a scope
can be divided into four groups.
(1) Housekeeping (on/off, brightness, focus)
(2) Horizontal (X position, X amplitude, time/division)
(3) Vertical (Y position, Y amplitude, Invert, Volts/division)
(4) Trigger/synchronisation (level, +/-, external, ac/dc/lf/hf, tvh/tvv)
Set any controls marked "calibrate" to the correct position.
Adjust the housekeeping controls to obtain a trace (display).
Adjust the vertical and horizontal controls to display a few cycles of a waveform.
Adjust the trigger/synch controls to make the display stationary.
It is best to display about two cycles and make them as large in height as possible.
Measure the amplitude and periodic time (time of one cycle). See below.
Calculate the frequency.
|In the diagram the waveform
is 4 divisions high.
The volts/ division switch is set to 50 mV/division.
The amplitude is therefore 4 x 50 mV = 200 mV.
The width of one cycle (indicated between the two red dots) is 4 divisions.
The time/division switch is set to 5 mS/division.
The periodic time is 4 x 5 mS = 20 mS.
Note that one cycle is the time between the start of a waveform and the point where it starts to repeat itself.
Frequency can be calculated by dividing 1 second by the periodic time.
Note that if the periodic time is in mS then 1 second has to be expressed as 1000 mS.
1000mS/20mS = 50 Hz
The pattern of squares is called a GRATICULE.
Copyright Graham Knott 1999