# Rulers

### What it does

You can use Rulers to take measurements between different points on your waveforms, including those created by your Channels, Math channels and Reference waveforms.

There are three different types of rulers: Horizontal rulers, Vertical rulers - together known as Graph rulers - and Phase rulers. Every axis within each of your PicoScope Views has a pair of either Horizontal rulers or Vertical rulers associated with it.

Every graph ruler consists of a dashed line at right angles to its measurement axis that indicates its position and a handle that you use to position it. The ruler’s position on the measurement axis is indicated by a value within its handle.

Vertical rulers are aligned vertically with your view. They indicate the value of single points on the view’s horizontal axis. As such, they respectively indicate either time, frequency or some other measurement depending on whether you are using them in scope, spectrum or X-Y view. As scope views are the most common view and have time-based horizontal axes, Vertical rulers are sometimes called time rulers.

Horizontal rulers are aligned horizontally with your view. They indicate the value of single points on one of your Channels’, Reference waveforms’ or Math channels’ measurement axes. Horizontal rulers are sometimes called signal rulers.

Phase rulers indicate key reference points with respect to a waveform in a scope view. When used in conjunction with the Graph rulers, you can see how the waveform changes relative to these key points. You can choose whether the Phase rulers indicate the phase boundaries of a rotational cycle (0-360° or 0-720°), a percentage (0 - 100%) or some other customisable measure. You can use Partitions to subdivide and visually indicate other known phases (e.g. 90° and 180°) between the key reference points and Wrap to choose whether to repeat (wrap) the phase values or continue to linearly increase and decrease them as you move up and down the horizontal axis.

The Rulers overview dialog displays a value for every active ruler on an axis and, where both axis rulers are active, the difference between them. When two Vertical rulers are active, the Rulers overview inverts the difference between their values to respectively indicate either the equivalent frequency or time difference between them, depending on whether they are in a scope view or spectrum view. In addition, the equivalent Revolutions Per Minute (RPM) is displayed. Finally, when both Phase rulers and Vertical rulers are active in a view, the Rulers overview also displays the phase values (and difference) indicated by the Vertical rulers.

Typically, you assess waveforms by looking at their specific features to see whether they occur at the right time or have the correct values. It can be tricky to do this accurately and precisely just by eyeballing a waveform. However, by moving Rulers into position at or around the feature of interest, you can combine the ease of visual assessment with precise and accurate measurements, particularly when used in combination with the Zoom tool.

Graph rulers are also used in conjunction with Measurements. For example, by adding two Vertical rulers onto a crankshaft position sensor waveform to delineate one complete engine cycle and Horizontal rulers to set appropriate thresholds, you can use a Falling (or Rising) edge count to determine the number of teeth associated with the crankshaft sensor operation. At the same time, the Rulers overview shows the engine speed (RPM) associated with the time difference between the two Vertical rulers.

When analysing the in-cylinder pressure occurring during a four-stroke cycle it is useful to place a Horizontal ruler at 0 bar to indicate when the pressure is above or below atmospheric pressure. You can move a Horizontal ruler to this exact location by typing 0 into its value field within the Rulers overview.

Phase rulers are especially useful when analysing how the four-stroke internal combustion engines operate relative to a 720° cycle of crankshaft rotation. By visually partitioning the graph area bounded by the phase rulers, Partitions helps you to identify each of the engine phases when looking at waveform patterns arising from events within a single cylinder (e.g. in-cylinder pressure waveforms). Similarly, when looking at waveform patterns arising from events across several cylinders (e.g. a relative compression waveform), Partitions can be used to separate out each cylinder’s contribution to the overall waveform (by using it to create a partitioned segment for each cylinder).

By adding Vertical rulers to the view when Phase rulers are active, the Rulers overview will also display values referenced to the Phase rulers. This is especially useful when working out timing events in terms of degrees of crankshaft rotation.

### How to use it

Open the Rulers panel by clicking the Rulers icon.

Click On under Graph rulers to add pairs of Horizontal rulers and Vertical rulers to the axes in your view. Drag the rulers to the desired locations.

In addition, you can add a horizontal ruler by dragging its handle down from the top of each vertical axis and a vertical ruler by dragging its handle from the bottom right-hand corner on the horizontal axis. Alternatively, type the desired position value (e.g. 0.0) within the ruler’s value field within the Rulers overview and the ruler will move to that position when you press Enter.

Click On under Phase rulers to add a pair of Phase rulers to your view. Reposition the Phase rulers by dragging their two pairs of double arrows to the two points you would like to use as the reference points marking the beginning and end of a phase. For example, if viewing an in-cylinder pressure waveform measured during a 4-stroke engine cycle, you can place one phase ruler on the peak of one compression tower and the other on the peak of the next to indicate the 720° total phase difference between them.

Closing the Rulers overview removes every active Graph ruler or Phase ruler from the view.