Tektronix 511A, Инструкция по эксплуатации

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CALIBRATION
While the cathode ray oscilloscope is usually em ­
ployed only as a qualitative rather than a quantitative
device, it is the only instrument capable of making many
types of measurements on non sinusoidal wave shapes.
To aid
in
this
work,
the Type
511
A has a
SIGNAL
CALI ­
BRATE switch so that either the three built-in line fre ­
quency calibration voltages or an external source may
be substituted for the signal to be measured.
SIGNAL CALIBRATE SWITCH
This switch permits the vertical deflection system of
the oscilloscope to be conveniently changed from the
SIGNAL INPUT connector to four different sources of
calibrating voltages. In the EXT. CAL. position it is
connected to the binding post marked CAL. INPUT,
which in turn may be connected to a suitable source of
known voltage. In the X. 1 position it is connected to the
arm of the CAL. VOLTAGE potentiometer, furnishing
from 0-1 V, peak to peak. The scale on the CAL. VOLT­
AGE control is accurate to ±5% of full scale with
normal line voltage (117 V). When a more accurate
knowledge of the calibrating voltage is needed, a volt ­
meter may be connected to the binding post marked
CAL. OUTPUT. The CAL. VOLTAGE control is a 5 K
potentiometer, so that a reasonably high resistance volt ­
meter should be used. In any case however, the reading
on the meter is the voltage actually applied. The other
two switch positions, X 1
and X10, furnish
ranges of 0-10
and 0-100 volts respectively.
The CAL. INPUT binding post may be used as an
auxiliary signal input. This connection is not recom­
mended for observing high speed transients, due to the
slightly greater capacity and lack of a parasitic sup ­
pressor.
MEASUREMENT OF SIGNAL AMPLITUDES
To measure the amplitude of any signal under ob­
servation, adjust the size of the image to correspond to
a convenient pair of horizontal lines on the graticule.
Move the SIGNAL CALIBRATE switch to the appropriate
source of calibration voltage and adjust its output until
the image matches the same graticule lines to which
the signal had been previously set. The calibration volt­
age is now equal to the signal amplitude.
CAUTION —
IF
THE INPUT PROBE ( ATTEN.
10X) IS USED, THE SIGNAL AMPLITUDE
IS
EQUAL
TO TEN-TIMES THE CALIBRA ­
TION
VOLTAGE.
The scale on the CAL. VOLTAGE potentiometer is
calibrated in peak to peak volts. If a sine wave is being
measured, this may be converted to R.M.S. by dividing
by 2.828. If a voltmeter is used to measure the CAL.
OUTPUT, remember to multiply its R.M.S. by 2.828 to ob ­
tain a peak to peak reading.
CAUTION — DO NOT OVERLOAD THE
AMPLIFIERS WHEN MAKING AMPLI ­
TUDE MEASUREMENTS.
Another method which is less accurate but more rapid
is to calibrate the oscilloscope itself. Select a suitable
convenient
voltage in the range needed,
for
example
10 volts, and adjust the VERT. AMPL. ATTEN. until a
convenient deflection, say 5 scale divisions, is obtained.
The sensitivity is now 2 volts per division and ampli ­
tudes may be read directly. The range may be extended
if desired by the INPUT ATTENUATOR and probe which
has an attenuation of 10X.
CAUTION — THE DEFLECTION POLARITY
SWITCH MUST BE IN THE NORMAL
(CENTER) POSITION DURING CALIBRA­
TION TO PREVENT ERROR IN THE INDI­
CATED AMPLITUDE.
INTENSITY MODULATION (Z AXIS)
If desired, signals may be impressed on the cathode
of the cathode ray tube thus modulating its brightness.
The CRT CATHODE binding post is connected to the
cathode via a .1 mfd capacitor. The cathode resistor
is 120 K. Since the time constant is only .012 sec. long,
square pulses cannot be transmitted without some
loss
of shape. Its primary purpose, however, is to transmit
short pulses such as timemarkers, etc.
SWEEP
OUTPUT
The SWEEP OUTPUT binding post makes available
the waveshape appearing on the plate of the sweep
generator tube. V10 is used as a cathode follower to
isolate the sweep generator from whatever is connected
to the SWEEP OUTPUT post. The amplitude is approxi­
mately 20 V peak to peak.
GATE OUTPUTS
V8 is used as a phase splitter to provide positive and
negative square waves of the same duration as the
sweep. The +GATE is taken from the cathode and DC
coupled, thus providing an accurately square topped
pulse even at the longest sweep times. The — GATE is
taken from the plate via a .05 mfd capacitor to remove
the DC component.
TYPE 511-A, 511-AD SECTION 2, PAGE 4