Tektronix CA PLUG-IN Instruction Manual page 8

Probe Adjustment
An adjustable capacitor compensates for slight
variations in input capacitance from one
strument to another. This capacitor is located
in the probe body in the P510, P410( and in
the termination block at the instrument end
o f the cable in the P6017.
few seconds to check this adjustment, and it
is a good practice to make this check each
tim e the probe is to be used. Simply touch
the probe to the oscilloscope calibrator-output
terminal and observe the calibrator waveform
on the screen. If necessary, adjust thetrim m er
fo r a flat top on the calibrator square wave.
To adjust the Type P6000 probe, touch the
probe tip to the calibrator output connector
and display several cycles of the calibrator
waveform. If the top and bottom of the dis-
played waveform is not flat, loosen the locking
ring by turning it in a counterclockwise direc-
tion. Rotate the barrel of the probe as neces­
sary to compensate the probe. Tighten the lock­
ing ring carefully after compensating the probe,
being careful not to disturb the probe adjustment.
Input Coupling
It is sometimes undesirable to display the de
level of the waveform being observed. Placing
the AC-DC switch in the AC Position inserts
a capacitor in series with the input so the
de component of the waveform
and only the ac component is displayed. The
low-frequency response is about 2 eps when ac
coupling is used.
Output Polarity
It w ill be desirable to invert the displayed
waveform at tim es, particularly when using
the dual-trace feature of the Type CA. The
P O L A R IT Y switch has two positions.
NORMAL position the displayed waveform w ill
have the same polarity as the input Signal.
In the INVERTED position the displayed wave­
form w ill be tumed upside down; that is, a
positive-going pulse
negative going pulse.
DC Balance Adjustment
After the plug-in unit has been in use for
a period of time you w ill notice that the trace
w ill change position as the VARIABLE control
is rotated. This is caused by tube aging and
2-2
I n ­
It takes only a
is blocked
In the
w ill be displayed as a
Operating Instructions - Type CA
the resultant shift in operating potentials. To
correct this condition see Calibration Section.
Gain Adjustment
Aging of the tubes w ill also affect the gain
o f the plug-in unit.
fo r this adjustment.
Positioning Adjustment
The Vert Pos Range control balances the de
output level so the full ränge of the front-
panel positioning Controls can be utilized. See
Calibration Section for this adjustment.
Types of Operation
Generally, three types of Operation w ill be per-
form ed using the Type CA ünit; ALTERN ATE,
C HOPP ED, and ADDED ALGEBRAICALLY. The
three types of Operation
different so we w ill examine them in the order
stated.
ALTERNATE
Connect the two Signals to be compared to
the two Signal inputs and turn the MODE switch
to A ONLY. Set the sweep up for triggered
Operation and adjust the VOLTS/CM and VER-
T IC A L POSITION Controls
display the waveform. Turn the MODE switch to
B ONLY and adjust the corresponding Controls
as necessary to display the other waveform.
Now tum the MODE switch to ALTERNATE.
If necessary, touch up the oscilloscope's sweep
triggering Controls to obtain a stable image.
Both waveforms w ill now be displayed on the
ert screen. As the control of each amplifier
is independent you can position, attenuate, or
invert the Signals as necessary to compare
their shape, relative amplitudes, etc.
Use the AC LF REJECT triggering mode
and ALTE R NATE sweeps for INTernal tr ig ­
gering on Signals having components above
10 kc. F or lower-frequency Signals, use the
AC triggering mode.
Position, an rc filter is inserted into the Cir­
cuit allowing it to recover quickly from the
de level changes encountered with the A L T E R ­
N ATE sweep. To compare the phase difference
between two Signals,
externally using the reference Signals as the
trigg e r Signal.
See Calibration Section
are fundamentally
as necessary to
In the AC LF REJECT
you should trigger
AA