Voltage Measurements - Tektronix 502A Instruction Manual

Magnifier
To expand a particular part of the display horizontally,
first use the Horizontal
the desired part of the
graticule. Then turn the HORIZONT L DISPL Y switch to the
magnification desired. The portion of the display at the
center of the graticule will then be expanded 2, 5, 10, or
20 times depending on the setting of the HORIZONT L
DISPL Y switch. t the same time, the SWEEP M GNIFIER
ON indicator lamp will light, indicating that the display has
been expanded. ny portion of the original unmagnified
display can then be shown by rotating the Horizontal POSI ­
TION Control.
HOR ZONTAL
D SPLAY
HOR ZONTAL
Fig. 2-9. Magnified sweep. The portion of the waveform at the
vertical centerline remains stationary as the sweep is magnified.
The displayed waveform is expanded left and right from the center-
line. The lower waveform is a two times magnification of the upper
waveform.
In magnified sweep operation, the sweep rate is multiplied
by the magnification. This means that the time per centi ­
meter indicated by the TIME/CM switch must actually be
divided by the magnification to obtain the correct time re ­
quired for the sweep to move one centimeter. For example,
if the TIME/CM switch is set at 5 mSEC, and the magnifier is
set at X5, the true time per centimeter is 5 milliseconds
divided by 5, or 1 millisecond per centimeter.
POSITION Control to position
display to the center of the
Operating
Magnified sweep rates are all calibrated within 3% ac ­
curacy so long as their true time per centimeter is 1 mico-
second or more. Sweep rates faster than this are uncali ­
brated and may be nonlinear. The SWEEP M GNIFIER UN ­
C LIBR TED indicator lamp lights whenever the maximum
calibrated sweep rate is exceeded, to indicate that the sweep
is uncalibrated.
X-Y Operation
On the Type 502 , it is possible to horizontally deflect
one or both of the spots across the screen by means of some
externally derived waveform, rather than by means of the
internal sweep circuits. This permits
be used for either single or dual-beam X-Y curve tracing.
For single-beam applications
and vertical-deflection factors
BE M amplifier can be switched to the crt horizontal deflec ­
tion plates by placing the HORIZ DEF PL TE SELECTOR
switch at the UPPER BE M
tion provides .1 mVOLTS PER CM to 20 VOLTS PER CM sen ­
sitivity and differential input for both horizontal and vertical
deflection. The LOWER BE M is used for vertical deflection
while the UPPER BE M is automatically positioned off the
screen while waiting for an input signal.
indicates when the UPPER BE M amplifier is connected to
the horizontal deflection plates.
For dual-beam X-Y applications, an external waveform can
be applied to the horizontal amplifier by connecting the
waveform to the EXTERN L Horizontal Input Connector. The
horizontal deflection sensitivity is controlled by the setting of
the HORIZONT L DISPL Y switch, which has a maximum
sensitivity of .1 v/cm. The HORIZ DEF PL TE SELECTOR
switch must be in TIME B SE
X-Y applications.

Voltage Measurements

ccurate voltage measurements of inputs to the vertical
amplifiers can be made using the calibrated deflection fac ­
tor feature of the Type 502 .
tell you how to use the oscilloscope for this purpose and
how to obtain the greatest possible accuracy in your mea ­
surements. It is important that proper techniques be used
in order that errors are not introduced in the results.
During voltage measurements, you should always display
the waveform across as much of the crt face as is possible
since, as a general rule, the accuracy of your measurements
will increase as the vertical size of the displayed wave ­
form is increased. In measuring voltages, it is important
to remember that the width of the trace may be an appreci ­
able p rt of the over ll measurement and care should be
used that the trace width is not included in the vertical de ­
flection readings you obtain. You should consistently make
all readings from one side of the trace. If the bottom side
of the trace is used for one reading, it should be used for
all succeeding readings.
Make sure the V RI BLE SENSITIVITY Control is
in the C LIBR TED position prior to any vertical
measurements, unless
instrument with the V RI BLE SENSITIVITY control.
nstructions — Type 502A
the oscilloscope to
where equal horizontal
are desirable, the
MP position. This type of opera ­
panel light
MP position for dual-beam
The following instructions
NOTE
you have calibrated
UPPER
the
2-7