Tektronix 11801C User Manual page 204

Enhanced Accuracy
3 54
H Delay Adjust lets you deskew different sampling heads to any one
sampling head. The reference head you choose is measured, and the
delay of the other sampling heads is adjusted to match that reference
head. Calibrate delay adjust only when you need to measure delays
between two sampling heads to close tolerance. When the Delay Com
pensate selector is set to Off, compensation of the sampling head
delays is not done automatically and the deskew calibration is not
maintained automatically by the system. This calibration parameter is
unique in that the delay adjust does not apply to individual channels but
to the sampling head as a whole. The delay adjust value is not stored in
the sampling head, but in the instrument mainframe, and there is no
factory default value.
Typical Calibration Method
The five available sampling head calibrations are made in a similar way. The
following description is of the options used when making a typical calibra
tion. Further discussion of the manual method of making each individual
calibration follows the description of the typical method.
To make a sampling head calibration, touch the selector in the Enhanced
Accuracy major menu that names the parameter you want to calibrate.
These include Blowby Compensate, Gain, Offset, Delay Adjust, and TDR
Amplitude. Each of these displays a pop up menu. All of these pop up
menus are similar, and the illustration on the next page of the Offset pop up
menu is typical of these menus.
When you use these pop up menus, you first select the sampling head
channel you want to calibrate. The left side of the pop up menu is reserved
for this. The Selected Channel line at the top of this section shows which
channel is currently selected. You can use the selectors in this section to
change the selected channel. See Figure 3 24.
Many of the calibration controls on the right of the pop up menu are com
mon to all five of the pop up menus. All these common selectors operate
similarly, and give you the same options for each calibration.
Each of the calibrations can be made manually or automatically. In addition,
you can set the calibration to the factory default or to be the same as a
calibration you made earlier.
Reference