Tektronix 310A, Инструкция по эксплуатации, Страница: 25 / 132

Operating Instructions-Type 310A
2. Set the T IM E /D IV switch and the Variable T IM E /
D IV control so one cycle of the signal covers an exact
number of horizontal divisions. Do not change the Variable
T IM E /D IV control after obtaining the desired deflection.
This display can be used as a reference fo r frequency com­
parison 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 T IM E /D IV switch, the repetition rate of
the reference signal must be known. If it is not known, it
can be measured before the Variable T IM E /D IV switch is
set in step 2.
in seven horizontal divisions can be determined by using the
repetition rate formula (step 6):
Repetition
Rate
= 50ps X 1.37 X 7 480 jus
This answer can be converted to frequency by taking the
reciprocal o f the repetition rate (see application on Deter­
mining Frequency).
Time-Duration Measurements
To measure time between tw o points on a waveform, use
the follow ing procedure:
4. Divide the repetition rate o f the reference signal (sec­
onds) by the product o f the horizontal deflection estab­
lished in step 2 (divisions) and the setting of the T IM E /D IV
switch. This is the horizontal conversion factor.
1. Connect the signal to the vertical INPUT connector.
2. Set the V O LTS/D IV switch to display about fo ur
divisions o f the waveform.
reference signal repetition rate (seconds)
horizontal T IM E /D IV
deflection X switch
(divisions) setting
5. To measure the repetition rate o f an unknown signal,
disconnect the reference signal and connect the unknown
signal to the vertical INPUT connector. Set the T IM E /D IV
switch to a setting that provides sufficient horizontal de­
flection to make an accurate measurement. Do not readjust
the Variable T IM E /D IV control.
6. Measure the horizontal deflection in divisions and
calculate the repetition rate of the unknown signal using
the following formula:
Horizontal
Conversion =
Factor
Repetition
Rate
T IM E /D IV horizontal horizontal
switch X conversion X deflection
setting factor (divisions)
NOTE
If the horizontal magnifier is used, be sure to use the
magnified sweep rate in place of the T IM E /D IV
switch setting.
3. Set the triggering control to obtain a stable display.
4. Set the T IM E /D IV switch to the fastest sweep rate
that displays less than eight divisions between the time
measurement points (see Fig. 2-11). (See the topic entitled
Horizontal Sweep Rate in this section concerning non­
linearity o f first and last divisions o f display.)
Fig. 2 -1 1 . Measuring the tim e du ratio n between points on a wave-
form .
Example. Assume a reference signal frequency of 455
hertz (repetition rate 2.19 milliseconds), a T IM E /D IV
switch setting o f .2 ms and the Variable T IM E /D IV control
is adjusted to provide a horizontal deflection o f eight d ivi­
sions. Substituting these values in the horizontal conversion
factor form ula (step 4):
Horizontal
Conversion =
Factor
2.19 milliseconds
. 2 X 8
1.37
Then, w ith a T IM E /D IV switch setting of 50 [xs, the repe­
titio n rate of an unknown signal which completes one cycle
5. Adjust the V E R TIC A L POSITION control to move
the points between which the time measurement is made to
the center horizontal line.
6. Adjust the HO RIZO NTAL POSITION control to cen­
ter the time-measurement points w ithin the center eight
divisions o f the graticule.
7. Measure the horizontal distance between the time
measurement points. Be sure the V A R IA B LE T IM E /D IV
control is set to C ALIBRATED.
8. M ultiply the distance measured in step 7 by the set­
ting of the T IM E /D IV switch. If sweep magnification is
used, divide this answer by 5.
2-17