Tektronix 535A, Instruction Manual

Page: 25 / 156

Applications —Type 535A
Horizontal Distance
__ Time
Time/cm Switch Setting
Sweep Magnification
Fig. 3-3. Measuring time interval between events displayed on the oscilloscope screen.
then, 3 centimeters multiplied by .2 volts per centimeter
gives you an indicated .6 volts. Since the voltage point is
above the voltage reference line the polarity is indicated to
be positive. The indicated voltage multiplied by the probe's
attenuation factor of 10 then gives you the actual voltage of
positive 6 volts.
Time Measurements
The calibrated sweeps of the Tye 535A Oscilloscope
causes any horizontal distance on the screen to represent a
definite known interval of time. Using this feature you can
accurately measure the time lapse between two events dis­
played on the oscilloscope screen. One method which pro­
duces sufficient accuracy for most applications is as follows
(see Figure 3-3):
1. Using the graticule, measure the horizontal distance be­
tween the two displayed events whose time interval you
wish to find.
2. Multiply the distance measured by the setting of the
appropriate TIME/CM control to obtain the apparent time
interval. (The VARIABLE TIME/CM control must be in the
CALIBRATED position).
3. Divide the apparent time interval by 5 if the magnifier is
on, and 1 if the magnifier is off, to obtain the actual time
interval.
For example, assume that the TIME/CM switch setting
is 1 MILLISEC, the magnifier is on, and that you measure a
horizontal distance of 5 centimeters between events. In this
example then, 5 centimeters multiplied by 1 millisecond per
centimeter gives you an apparent time interval of 5 milli­
seconds. The apparent time divided by 5 then gives you the
actual time interval of 1 millisecond.
Another method for measuring time intervals involves the
use of the delayed sweep feature of the Type 535A. In
this method the HORIZONTAL DISPLAY switch is placed
in the 'B' INTENSIFIED BY ‘A’ position to brighten a portion
of the trace. The brightened portion of the trace and the
DELAY TIME MULTIPLIER control are then used to make the
time measurements. This method provides a very high de­
gree of accuracy when care is taken in making the mea­
surements. The method is summarized as follows:
1. Place the HORIZONTAL DISPLAY switch in the B' IN­
TENSIFIED BY ‘A’ position and adjust the Time Base B trig­
gering controls for a stable display of the input waveform.
Adjust Time Base A for free-running operation.
2. Turn the intensity down until the brightened portion of
the trace is easily distinguishable. Adjust the Time Base
A TIME/CM controls to reduce the brightened area to a
small spot or to cover as small a portion of the trace as
possible.
3. Using the DELAY TIME MULTIPLIER control, position the
start of the brightened portion to the beginning of the inter­
val you wish to measure. Record the setting of the DELAY
TIME MULTIPLIER control.
4. Using the DELAY TIME MULTIPLIER control, position the
start of the brightened portion of the trace to the end of
the interval you wish to measure. Again record the setting
of the DELAY TIME MULTIPLIER control.
3-3