# PAM Levels RMS

PAM Levels RMS measures the RMS amplitude all levels of a PAM signal. The PAM signal must be displayed as a single-valued waveform with all four logic levels displayed. On NRZ signals, this measurement measures the zero and one levels.

Settings That Affect This Measurement
Setting | Description
--- | ---
PAM-N Analysis Setup Dialog Box Settings
Amplitude Units | Sets the amplitude units for measurement: volts, Watts, or percent.

## Setting the Timespan

You must set Infiniium's timespan wide enough so that each logic level is visible on the screen. For example, for a PAM4 signal this would be four levels (0, 1, 2, 3), for a PAM3 signal this would be three levels (0, 1, 2), or for an NRZ signal this would be two levels (0, 1). Failure to set the timespan wide enough results in an error. Consider the following items when setting the timespan:

- If multiple identical levels are displayed, the level that is present for the longest time will be selected for measurement. For example, if two logic levels are shown on the waveform, with one being 100 ps and the other being 150 ps, the 150 ps level is selected to be measured.
- To be considered a measurable level, the level must include at least 50% of the leading and trailing edges.

## Measurement Algorithm

1. Identify one of each of the longest "n" logic levels on a PAMn signal or two levels on an NRZ signal.
2. For each level, measure the RMS value of each data point over time.
3. For each level, determine the average RMS value of all of the level's data points.

## To measure

1. Click Auto Scale in the menu toolbar.
2. Adjust the time scale so that at least one of each of the four possible PAM levels or two of NRZ levels are displayed. Any number of the same level can be displayed, but there must be at least one of each level displayed.

If the timespan is too narrow, the measurement results panel displays Region? or Level? instead of a measured value. Increase the timespan.

3. Click the toolbar's PAM tab.
4. On the toolbar, locate and click the Levels RMS button.
5. Select the Region in which to make the measurement:
   - Displayed Waveform — is what you see in the waveform window (which can be a zoomed-in view of the complete waveform).
   - Entire Waveform — specifies the complete waveform.
   - Region N — If regions are enabled for the selected signal, you can select one of those regions.

## SCPI Command

`:MEASure:PAM:RMS`