Tektronix CSA8000B - Manual (Page 322)

Measurement Reference Parameters and Methods
B- 60 CSA8000B & TDS8000B User Manual
RZ Sources
The automatic measurement system uses the following levels when measuring
RZ source waveforms. For the RZ measurements, and their definitions that use
the levels described here, see page B--15.
The following levels are used when deriving measurements on RZ waveforms.
TcrossL
Low reference
TcrossH
High reference
Figure B- 6: RZ measurement reference levels
RZ Measurement
Reference Levels