# Tracking Markers

Tracking markers measure the position and magnitude at any sample point on a single-valued waveform. Tracking markers can be placed on Waveform, Freq-Mag, Phase, GrpDelay, Time-Ohms, Time-Volts, and Time-% waveform content windows.

When a tracking marker is placed on a Freq-Mag, Phase, and GrpDelay window, it appears on the same x position on all three of these windows.

For multi-valued waveforms, like eye diagrams, use manual line markers.

Click to select the tracking marker. Tracking markers are designed for single-valued waveforms. Waveform tracking markers track the waveform at the position determined by the X-axis marker. A small box appears at the intersection of the X and Y markers. This box moves along the waveform as you reposition the X-axis marker on the display graticule. When using waveform tracking, the manual markers are unavailable. Waveform tracking is disabled and manual marker mode is enabled when the Y-axis marker is turned on.

## Using Tracking Markers

There are several ways to turn on tracking markers:

- Click Measure > Markers... to open the Markers dialog box (shown above), and select the Tracking Markers tab. In the dialog box, click one of the four available tracking marker button so that it turns blue. The marker is now turned on. Select the Source Waveform on which to place the marker.

  Tracking markers are not available for eye diagram waveforms, but Manual Line Markers are.

- Click the quick access toolbar button .

- On an oscilloscope, press the front-panel [Marker] key.

- On an oscilloscope, press the front-panel horizontal Marker Position knob.

You can simultaneously use both tracking markers and manual line markers on Waveform content windows (non-spectral graphs). However, turning on a tracking marker disables the associated manual line markers. For example, turning on tracking marker 2 disables manual markers X2 and Y2.

To move a displayed marker:

- You can also simply drag the marker line or marker handle . Depending on the display window view, the marker handle may not be visible. For exact marker positioning, enter the marker value directly in the Markers dialog box.

- You can move markers using the front-panel horizontal Marker Position knob. When multiple markers are displayed, pushing the Marker Position knob selects an active marker for positioning. Repeatedly push the Marker Position knob to move through all active markers. See Oscilloscope Front Panel Marker Controls.

## Reference Marker and Markers Table

When multiple markers are turned on, you can measure the time and magnitude difference between any two waveform locations. The first marker becomes the reference marker, and the position of all subsequent markers is measured relative to the location of the reference marker.

As shown in the above picture, the selected marker has a solid handle background and, in the Markers table, the reference marker is identified by the icon.

To show or hide the Δ Pos (delta position), Δ Mag (delta magnitude), and 1/Δ Pos (reciprocal of delta position) values in the Markers table, click Show Δ Values.

Click Setup to open the Markers dialog box.

To change the reference marker:

- Use the dialog box's Reference Marker field.
- In the Markers table, click the marker entry beneath the Marker heading.

Marker values are based on the units of the source waveform. The marker resolution is limited to the resolution of the display.

If you adjust the waveform's horizontal position, the markers will move with the waveform, and the marked position value does not change, even if the marker is moved off the screen.

The marker buttons are also enabled whenever Histogram Windowing or Mask Test Scaling is enabled. You can then use the marker knobs to adjust the marker lines.

## Markers and Waveform Sampling Points

When positioning a tracking marker between waveform sampling points, the marker's time position and associated y-axis value may be restricted. Because there is normally an abundance of waveform sampling points on screen, you may seldom notice that a marker is restricted to specific positions and values.

Tracking Marker Positions and Values
Marker X-Axis Position | Marker Y-Axis Value
--- | ---
Non-Spectral Waveforms
restricted to sampling- point position | nearest sampling- point value
Spectral Waveforms (such as created by the FFT function)
always restricted to sampling-point position | always nearest sampling-point value

To observe markers restricted to sampling points:

1. Select single-sweeps.
2. Open the Waveform tab of the Acquisition dialog box, and set the Samples/Waveform setting to 16 sample points.
3. Open the Display Setup dialog box and turn the Connect Waveform Points setting off.
4. Drag the tracking marker using the marker handle , and you will see that the marker can only be positioned on sampling points. You can also click the position arrows in the dialog box. If you enter a specific marker position in the dialog box's Position field, the marker will move to the entered location but the amplitude value will be equal to the amplitude at the nearest sampling point.