Applications; Measurement Techniques - Tektronix 7B51 Instruction Manual

APPLICATIONS
General General
The following information describes the procedures and
techniques for making basic measurements with a 7500-
series Oscilloscope_ These applications are not described in
detail, since each application must be adapted to the
requirements of the individual measurement_ This instru-
ment can also be used for many applications not described
in this manual. Contact your local Tektronix Field Office
or representative for assistance in making specific measure-
ments. Also, the following books describe oscilloscope
measurement techniques which can be adapted for use with
this instrument:
Harley Carter, "An I ntroduction to the Cathode Ray
Oscilloscope", Philips Technical Library, Cleaver-Hume
Press Ltd., London, 1960.
J. Czech, "Oscilloscope Measuring Techniques",
Philips Technical Library, Springer-Verlag, New York,
1965.
Robert G. Middleton and L. Donald Payne, "Using
the Oscilloscope in Industrial Electronics", Howard W.
Sams & Co. Inc., The Bobbs-Merrill Company Inc.,
Indianapolis, 1961.
John F. Rider and Seymour D. Uslan, "Encyclopedia
of Cathode-Ray Oscilloscopes and Their Uses", John F.
Rider and Publisher Inc., New York, 1959.
John F. Rider, "Obtaining and Interpreting Test
Scope Traces", John F. Rider Publisher Inc., New York,
1959.
Rufus P. Turner, "Practical Oscilloscope Handbook",
Volumes 1 and 2, John F. Rider Publisher Inc., New
York,1964.
Measurement Techniques
Sweep Rates. To establish an arbitrary horizontal sweep
rate based upon a specific reference frequency, proceed as
follows:
1. Connect the reference signal to the INPUT connec-
tor. Set the VOL TS/DIV switch for four or five divisions of
vertical deflection.
2. Set the TIME/DIV switch and the VARIABLE
TIME/DIV control so one cycle of the signal covers an
01
Operating Instructions-Type 7B51
exact number of horizontal divisions. Do not change the
VARIABLE TIME/DIV control after obtaining the desired
deflection. This display can be used as a reference for fre-
quency comparison measurements.
3. To establish an arbitrary sweep rate so the repetition
rate of an unknown signal can be measured accurately at
any setting of the TIME/DIV switch, the repetition rate of
the reference signal must be known. If it is not known, it
can be measured before the VARIABLE TIME/DIV switch
is set in step 2.
4. Divide the repetition rate of the reference signal
(seconds) by the product of the horizontal deflection
established in step 2 (divisions) and the setting of the
TIME/DIV switch. This is the horizontal conversion factor:
Horizontal
Conversion
=
Factor
reference signal repetition rate (seconds)
horizontal TIME/DIV
deflection X switch
(divisions) setting
5. To measure the repetition rate of an unknown signal,
disconnect the reference signal and connect the unknown
signal to the INPUT connector. Set the TIME/DIV switch
to a setting that provides sufficient horizontal deflection to
make an accurate measurement. Do not readjust the V AR 1-
ABLE TIME/DIV control.
6. Measure the horizontal deflection in divisions and
calculate the repetition rate of the unknown signal using
the following formula:
Repetition
Rate
TIME/DIV
switch X
setting
horizontal horizontal
conversion X deflection
factor (divisions)
NOTE
If the horizontal magnifier is used, be sure to use the
magnified sweep rate in place of the TlME!DIV
switch setting.
Example. Assume a reference signal frequency of 455
hertz (repetition rate 2.19 milliseconds), a TIME/DIV
switch setting of .2 ms, and the VARIABLE TIME/DIV
control adjusted to provide a horizontal deflection of eight
divisions. Substituting these values in the horizontal conver-
sion factor formula (step 4):
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