Time Interval Measurement - Tektronix 1S1 Instruction Manual

3. Measure the voltage as described above, using the
established zero-volt reference level as the point from which
to make all measurements.
If the applied signal has a relatively high dc level, the
zero-volt level and the input signal may be so far apart that
only one will be in the graticule viewing area. In this case,
use the DC offset method of voltage measurement as de-
scribed next.
DC Offset Voltage Measurement
The DC OFFSET control and the voltage available at the
OFFSET OUTPUT jack can be used to make accurate voltage
measurements of the input signal, whether or not the deflec-
tion factor of the Type 1S1 is calibrated.
Use the following procedure to make a measurement:
1. Obtain the desired sampling display through normal
operating procedures.
2. Position the bottom of the waveform (or other desired
reference portion) to the graticule centerline with the VERT
POSITION and/or DC OFFSET control.
3. Measure the voltage at the OFFSET OUTPUT with an
accurate high-impedance voltmeter or a monitor oscilloscope.
This voltage is 10 times the applied offset voltage.
4. Using only the DC OFFSET control, position the top of
the waveform (or other level to be compared) to the graticule
centerline.
5. Again measure the OFFSET OUTPUT voltage.
6. Determine the voltage difference between the two
measurements. If the voltage polarity has reversed, add the
two measurements.
7. Divide the measured voltage difference by 10 to obtain
the voltage difference at the SIGNAL IN connector. If the
input signal path includes an attenuator, multiply the input
signal voltage by the attenuation factor to obtain the volt-
age difference at the signal source.
TIME MEASUREMENTS
The calibrated equivalent-time sweep rates of the Type
1S1 make any horizontal distance on the crt screen represent
a specific interval of time. Thus the time lapse between any
two events on an input signal can be measured directly from
the waveform displayed on the crt screen. The sweep rate
most convenient for measuring the input signal can be select-
ed with the Type 1S1 TIME/CM switch. Set the sweep rate
so the portion of the waveform containing the points of
interest is spread over several cm of the graticule.

Time Interval Measurement

Basic sweep accuracy of the Type 1S1 is ±3% when the
oscilloscope horizontal deflection factor is set to 1 volt/cm.
Increased accuracy of time measurements can be obtained
by checking the timing of the particular sweep rate to be
used.
To make a time measurement between two points on a
displayed waveform:
Operating Instructions – Type 1S1
1. Measure the horizontal distance in centimeters and
fractions of centimeters between the two points on the wave-
form. Be sure the Time/Cm VARIABLE control is in CAL
(counterclockwise detent) position.
2. Multiply the number of cm of horizontal deflection by
the sweep rate indicated on the Type 1S1 TIME/CM switch.
Fig. 2-19. Time interval measurement.
Example: 4.2 cm X 0.5 nsec/cm = 2.1 nsec.
Fig. 2-19 illustrates an example of a time interval measure-
ment. The horizontal deflection of 4.2cm is multiplied by
the sweep rate of 0.5 nsec/cm to obtain a time interval
of 2.1 nsec.
Time Comparison Measurement
To make a time-comparison measurement between points
on two different waveforms, it is necessary to use an external
triggering signal for the time reference. The two input sig-
nals must bear a frequency relationship to each other and
to the triggering signal.
1. Connect one of the input signals to the SIGNAL IN
connector.
2. Connect the triggering signal to the EXT TRIG connector.
3. Set the TRIGGER SOURCE switch to EXT (±) and trig-
ger the display. Do not readjust the triggering controls until
after the time comparison measurement has been made.
4. Adjust the Type 1S1 TIME POSITION control to position
the point of interest on the waveform at some vertical
reference line (e.g. the vertical centerline). Now do not
readjust the TIME POSITION control until after the measure-
ment has been made.
5. Remove the first input signal and connect the second
signal. If the time relationship that is of interest is at the
signal source, use the same input cable or probe or use
another cable or probe that provides exactly the same
amount of time delay.
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