Setting The "Time-Base" of an Oscilloscope

The Time-Base or period of the graph is inversely related to the frequency of the signal.

1 / frequency = period
and
1 / period = frequency

For example a 1Hz signal will have a 1 sec period.  The screen of the Tektronix 2236 oscilloscope is divided into ten sections across.  The knob labeled SEC/DIV (seconds per division) is the one used to adjust the period of the graph.  When you are measuring the period of a signal with an oscilloscope you should expand the graph as large as possible so that you can still view one full cycle.  To do this turn the SEC/DIV knob until the time-base looks like it is as wide as it will get.  Once you have done this, count the number of horizontal divisions that one cycle of the graph fills.  Then you can take the reading from the SEC/DIV knob.  For example lets say that one cycle  of the graph takes up 4.3 divisions and the knob reads 1ms/div; this means that the period of the graph is 4.3ms, and the frequency is 232.5Hz.

18. Channel A and B SEC/DIV Switches
19. Channel A and B SEC/DIV Variable Control
20. X10 Magnifier Switch
21. Horizontal Mode Switch
22. Position Control
23. A/B SWP SEP
24. B Delay Time Position Control