# RN (rms)

RN (rms), Random Noise, is the root-mean-square value of the noise that is uncorrelated to the pattern and follows Gaussian statistics.

RN is measured using the following steps:

1. A particular bit is chosen from the pattern. Each time the measurement is made, a different bit is chosen.
2. The instrument acquires 4096 samples at the measurement location, which is normally the center of the bit. These samples are acquired precisely periodic in time at a rate close to the maximum instrument sampling rate.
3. The power spectral density of the resulting waveform is obtained. Because the signal is under-sampled, all periodic components are aliased down below half of the sampling rate.
4. The RN is calculated as the area of the power spectral density excluding any peaks in the spectrum (for example, the baseline noise of the power spectral density).
5. The above steps are repeated, and the power spectra from acquisition to acquisition are averaged together. The data from the one levels and zero levels are not combined.

The measurement is affected the RN Bandwidth selection in the Noise Measurements Tab.

An asterisk (*) may be shown with this measurement depending on the RN Compensation selection in the Advanced Tab.