The CRO is the electrical and electronic engineer's best
friend. So it's worth getting to know the instrument.

The CRO is connected in exactly the same way as a **
voltmeter**, i.e. in **parallel **with a component.

This is a typical display of a sinusoidal waveform on
the CRO screen:

The screen has a grid of 1
cm squares and the y-gain is marked in volt cm^{-1}. The
time-base is marked in ms cm^{-1} or
ms cm^{-1}.

This CRO screen shows the idea:

The horizontal scale is the
**time period**, measured in seconds, or, more usually, in **
milliseconds** (ms).

1 ms = **1 × 10**^{-3} s

We count how many squares
there are on the horizontal axis, then calculate the time by
multiplying the number of squares by the time per square.

**T = length (cm) ×
time-base (s cm**^{-1})

This time is the **period**. To get the **frequency**,
we need to take the **reciprocal** of the period.