Measurement Modes - Tektronix 11801C User Manual

Example 5: Taking Automated Measurements

Measurement Modes

Up to now, the measurements you have been using have been software
measurements. However, there are actually three measurement modes:
software mode, hardware mode, and statistics mode. In software mode,
measurements are taken from the digitized trace data record, the same data
that forms the trace on the display. In hardware mode, measurements are
taken from the analog signal output from the sampling head before it is
digitized and assembled into a trace record. The 11801C uses special timer
circuits to take hardware measurements. The advantage of hardware mea
surements is that they are performed faster than software measurements. In
statistics mode, measurements are taken from color graded waveform data
and are based on histograms computed at the crossing levels. You can use
statistical measurements to measure random" data such as eye diagrams.
You cannot take measurements in different modes on the same trace. If you
create two identical traces, you can take hardware measurements on one
and software measurements on the other. You can display only the measure
ments for the selected trace, however.
Table 2 1 compares the three types of measurements. It will help you deter
mine the best measurement type for your application.
Hardware measurements are specified using another alternate menu from
the Measurements pop up menu.
Step 22: Touch the Measurements selector in the major menu; then
touch Hardware Mode in the pop up menu.
2 60
Operating Basics