Tektronix 2213A Instruction Manual page 23

Operators Familiarization— 2213A Operators
level difference is more than 10 times the VOLTS/DIV
switch setting:
1. Set the Input Coupling switch to GND.
2. Insert the probe tip into the oscilloscope GND connec­
tor and wait several seconds for the input coupling capacitor
to discharge.
3. Connect the probe tip to the signal source and wait
several seconds for the input coupling capacitor to charge.
4. Set the Input Coupling switch to AC. The display will
remain on the screen, and the ac component of the signal
can be measured in the normal manner.