Tektronix 2245A Operator's Manual page 31

CH 1 AND CH 2 VOLTS/DIV VAR C on trols—Allow the CH 1 and
CH 2 vertical deflection factors to be increased up to at least 2.5
times.
Vertical deflection factors are greater than the VOLTS/DIV switch
setting when the UNCAL indicator is lit and a greater-than symbol (>)
is displayed to the left of the associated VOLTS/DIV readout. The
VOLTS/DIV settings are calibrated when the VAR control is in the fully
clockwise (detent) position.
UNCAL In dica tor—Lights when either CH 1 or CH 2 VOLTS/DIV set­
ting Is uncalibrated (variable function in e ffe c t).
SCOPE BW B u tto n —Reduces the bandwidth of the vertical deflec­
tion system and trigger system to 20 MHz when the button is lit. The
full vertical deflection bandwidth is available when the SCOPE BW but­
ton Is not lit.
CH 2 INVERT B u tto n —Inverts the Channel 2 input signal when the
INVERT button is lit.
The Channel 2 input signal in ADD mode and the Channel 2 trigger
signal pickoff are also inverted. A down-arrow symbol is displayed be­
tween the Channel 1 and Channel 2 VOLTS/DIV readout when the IN­
VERT mode is on.
COUPLING B u tto n s —Select the method of coupling input signals to
the Channel 1 and Channel 2 attenuators.
GND—Disconnects the input signal and grounds the input of the asso­
ciated vertical attenuator to provide a zero (ground) reference volt­
age display.
The COUPLING switch is In the ground position when the AC and the
DC buttons are not lit. A ground symbol ( rh ) is displayed to the right
of the associated VOLTS/DIV readout.
AC—Capacitively couples the Input signal to the vertical attenuator
when the AC button is lit.
Turning on AC Coupling turns off DC Coupling. AC Coupling blocks the
dc component of the input signal. The lower -3 dB frequency limit is
10 Hz or less when using either a IX probe or properly terminated
coaxial cable; it is 1 Hz or less using a compensated 10X probe. With
AC Coupling selected, an AC symbol ( A; ) Is displayed to the right of
the associated VOLTS/DIV readout. An ac symbol is also displayed
after the value readout of a CURSOR VOLTS measurement.
2245A Operators
Controls, Connectors, and Indicators
2-5