Tektronix T921 Instruction Manual page 105

This description includes the operation
and
maintenance of the added features of Option 1. For
all other information concerning the T922 or T922R,
refer to the appropriate section of this manual.
Schematic Diagrams for Option 1 are included at the
end of the Diagrams section in this manual.
Introduction
NOTE
OPERATING INFORMATION
The T922 or T922R Option 1 includes a fourth vertical
mode pushbutton (labeled DIFF) which, when pressed in
alone, inverts the CH 2 signal and displays the sum of the
CH 1 and CH 2 signals. (If the DUAL TRACE button is
pressed along with the DIFF button, CH 2 is inverted and
each signal is displayed but not summed .) The algebraic
sum (difference) of the CH 1 and CH 2 signals is a useful
feature for rejecting unwanted common-mode signals
such as line-frequency components . The DIFF button may
Option 1 Vertical Modes
(button in and display normal unless otherwise stated)
Options-T921/T922/T922R
T922/T922R OPTION 1 DIFFERENTIAL MODE
also be used in conjunction with other mode buttons to
provide a variety of modes as shown in the table .
DIFF Mode Operation
To operate the instrument in the DIFF mode, perform
the appropriate First Time Operation steps in Section 2 of
this manual, then :
1 . Connect the signal you wish to view to CH 1 input.
2. Connect a sample of the unwanted signal to CH 2
input.
3. Set: Vertical Mode DIFF
SOURCE For desired trigger
condition
4. Adjust the CH 1 and CH 2 VOLTS/DIV and VAR
controls to obtain the desired display (null of common-
mode signal) .
Option 1 Page 1
Vertical Mode Bu tton
Displayed Signal
Internal Trigger Source
DIFF & CH 2 __
CH 2 Inverted
CH 2
DUAL TRACE & DIFF
CH 1 and Inverted CH 2
CH 1
DUAL TRACE, DI FF ,& CH _2__ CH 1 and Inverted CH 2
__
CH 2
DUAL TRACE & CH 2
CH 1 and CH 2
CH 2
CH 1 ,& CH 2
CH 1 & CH 2 Alternate
_
CH 2
DI FF
Differential (CH 1 - CH 2)
CH 1
All Buttons Out
CH 1 & CH 2 Added CH 1