Technician Handbook ! 673 Electronic & Computer Controlled Systems Oscilloscope Scales An oscilloscope screen is divided by horizontal and vertical lines called divisions . When setting the display screen’s voltage scale, you specify how many volts you want each division to represent. In the example above, the signal voltage changes by 12 volts from low to high. The voltage scale in the screen in the illustration has only five divisions. To keep the signal trace from disappearing off the top of the screen, the technician has set this voltage scale to 5 volts per division (5 V/DIV). Other settings are possible (6 V/DIV, for example) that can also keep the entire signal visible.
Sometimes it requires a little experimentation to see which scale makes the signal easiest to evaluate. Setting the time scale appropriately is also important for being able to see a signal. In the first example above, the time scale has been set to 10 milliseconds per division (10 ms/DIV). This scale makes the signal’s 20 ms cycle very apparent. In the second example, a time scale of 1 ms/DIV zooms too far in so that only a tiny, unchanging snippet of the signal is visible. Once again, other appropriate time scale settings are possible (20 ms/DIV, for example) that can also display the signal characteristics clearly.
If settings aren’t specified for the signal you're monitoring, it may take some experimentation to find the best time scale setting. Technical Training 37