# PAM Eye Levels

The PAM Eye Levels measurement measures all three eye amplitude levels (vertical centers) of a PAM signal. On NRZ signals, the vertical center of the single eye is measured.

Settings That Affect This Measurement
Setting | Description
--- | ---
PAM-N Analysis Setup Dialog Box Settings
Receiver Sample Timing | Configures the timing for sampling the signal data for all PAM measurements. Depending on measurement conditions, this command may not affect the measurement.
Eye Center Location | Selects the basis for determining the location of an eye's center on the waveform: at maximum eye width or maximum eye height. Depending on measurement conditions, this command may not affect the measurement.
Eye Level Width | Defines the timespan (in percentage of symbol width) over which an eye's amplitude level is measured.
Amplitude Units | Sets the amplitude units for measurement: volts, Watts, or percent.

- See: Measurement Configuration Tab

This measurement can be applied to both PAM and NRZ waveforms.

## Measurement Algorithm

1. An autoscale is performed to determine if the signal is formatted as PAM or NRZ.
2. Determine the approximate signal-level amplitudes.
3. Locate the crossing (transition) regions on both sides of the eyes.
4. Determine the symbol period.
5. Find the center of each eye. Note that the Receiver Sample Timing setting determines if only the middle eye (Eye 1/2) is located or if all three eyes are located (Eyes 0/1, 1/2, and 2/3).

- If the Eye Center Location setting is set to Maximum Eye Width, determine the horizontal line (center amplitude) across the eye at the maximum eye width and find the time at the line's midpoint (center time).
- If the Eye Center Location setting is set to Maximum Eye Height, determine the vertical line (center time) across the eye at the maximum eye height and find the amplitude at the line's midpoint (center amplitude).

6. The Eye Level measurements are the amplitudes of the eye centers located above.

## To measure

1. Click Auto Scale in the menu toolbar.
2. Click the measurement toolbar's PAM tab.
3. On the toolbar, locate and click the Eye Levels button.

## SCPI Command

`:MEASure:EYE:PAM:ELEVel`