Tektronix 5A20N Instruction Manual page 8

Operating Instructions—5A20N
+ and — Input deflection; connector labeled —
Connectors indicates that a positive-going signal
{cont} will cause downward deflection.
Connectors include coded-probe in-
put rings for activation of X10
readout.
FIRST TIME OPERATION
Preparation
The first few steps of the following procedure are
intended to help place the trace on the screen quickly and
prepare the instrument for immediate use. The remainder
of the steps demonstrate some of the basic functions of the
5A20N. Operation of other instruments in the system is
described in the instruction manuals for those units.
1. Insert the unit all the way into the oscilloscope
system plug-in compartment,
clockwise and turn the oscilloscope system Power On. Pre-
division sweep rate and automatic triggering.
3. Set the SA20N front-panel controls as follows:
DISPLAY ON (readout illuminates)
POSITION Midrange
BANDWIDTH LIMIT 1 MHz (button out}
VOLTS/DIV Vv
STEP ATTEN BAL Midrange
— Input Coupling Dc, GND
NOTE
About five minutes is sufficient time for warmup
when using the 5A20N for short-term DC measure-
ments. For fong-term DC measurements using the
lower deflection factors, allow at least 15 minutes.
trace. The trace should appear near the graticule center,
f the maximum input voltage rating at the gates of
the input FET's is exceeded, the gates are diode-
clamped at about + or — 12.5 volts. If the signal
source can supply more than 1/16 A, the input pro-
tective fuse(s) will open,
2-2
6. Apply a 400-millivolt peak-to-peak signal (available at
the oscilloscope Calibrator loop) through a test lead or 1X
probe to the + input connector.
7. For DC-coupled, single-ended operation, release the
GND button associated with the + Input Coupling switch.
The display should be square waves four divisions in ampli-
tude, with the bottom of the display at the reference estab-
lished in step 5, Rotate the Variable Voits/Div control
counterclockwise out of its detent position, observing
reduction of the display. Return the Variable control to the
detent (CAL) position.
8. For AC-coupled, single-ended operation, re-position
the display with the POSITION control to place the bottom
of the display at the graticule centerline,
9. Push in the AC button and note that the display shifts
downward about two divisions to its average level.
10. Disconnect the coaxial cable from the + input con-
nector. Connect a dual input cable to the + and — input
connectors, then connect the coaxial cable from the Cali-
brator to the dual input cable.
11. For AC-coupled differential operation, set the — In-
put Coupling to AC (AC button in, GND button out). The
calibrator signal is now coupled to both inputs as a
common-mode signal. A straight line display should be
Step Attenuator Balance Adjustment
If this control is not properly adjusted, the CRT zero
reference point (trace or spot} will shift vertically due to
differential DC imbalance in the amplifier as the VOLTS/
DIV switch is rotated throughout its range. The shift is
more noticeable on the most sensitive positions.
a, With the instrument operating, ground both the + and
~ inputs (GND buttons pushed in) and move the trace to
graticule center with the POSITION control. Set the
VOLTS/DIV switch to 5 V.
b. Adjust the STEP ATTEN BAL control for minimum
trace shift as the VOLTS/DIV switch is rotated throughout
Gain Check
Whenever the 5A20N is inserted into a plug-in compart
ment other than the one in which it was calibrated, the