Tektronix 442, Инструкция по эксплуатации

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Operating Instructions—442 Service
EXAMPLE: Assume that the vertical distance
measured is 4.6 divisions (see Figure 2-13), the waveform
is above the reference line, and the VOLTS/DIV switch
reads 2 (read the appropriate VOLTS/DIV windowforthe
probe or cable being used).
Using the formula:
Instantaneous _
Voltage ~~
paring harmonic signals to a fundamental frequency, or
for comparing the repetition rate of input and output
pulses in a digital count-down circuit. The following
procedure describes how to establish arbitrary units of
measure for comparison measurements. Although the
procedure for establishing vertical and horizontal ar­
bitrary units of measurement is much the same, both
processes are described in detail.
vertical
distance
(divisions)
X polarity X
VOLTS/DIV
setting
Vertical Deflection Factor. To establish an arbitrary
vertical deflection factor based upon a specific reference
amplitude, proceed as follows:
Substituting the given values:
Instantaneous = 4 6 X + 1 X 2 V
Voltage
1. Connect a reference signal to the Channel 1 or
Channel 2 input connector. Set the SEC/DIV switch to
display several cycles of the signal.
The instantaneous voltage is 9.2 volts.
DIFF Mode Operation
With the VERT MODE DIFF button pressed in, the
displayed waveform is the difference between the signals
applied to the Channel 1 and Channel 2 inputs (CH1 — CH
2
) .
The following general precautions should be observed
when using the DIFF mode:
1. Do not exceed the input voltage rating of the
oscilloscope.
2. Set the VERT MODE switches to display the
selected channel, and set the VOLTS/DIV switch and VAR
control for that channel to produce a display of an exact
number of graticule divisions in amplitude. Do not change
the VAR control setting after obtaining the desired
deflection. This display can be used as a reference for
amplitude comparison measurements.
3. To establish an arbitrary vertical deflection factor so
the unknown amplitude of a signal can be measured
accurately at any setting of the VOLTS/DIV switch, the
amplitude of the reference signal must be known. If it is not
known, it can be measured before the VAR control is set in
step 2.
2. Do not apply signals that exceed the equivalent of
about eight times the reading of the VOLTS/DIV switch
settings, since high amplitude voltages may distort the
display. For example, with a VOLTS/DIV switch setting of
.5, the voltage applied to that channel should not exceed
about four volts.
Comparison Measurements
In some applications it may be desirable to establish
arbitrary units of measurement other than those indicated
by the VOLTS/DIV switch or SEC/DIV switch. This is
particularly useful when comparing unknown signals to a
reference amplitude or repetition rate. One use for the
comparison-measurement technique is to facilitate
calibration of equipment (e.g., on an assembly-line test)
where the desired amplitude or repetition rate does not
produce an exact number of divisions of deflection. The
adjustment will be easier and more accurate if arbitrary
units of measurement are established so the correct
adjustment is indicated by an exact number of divisions of
deflection. Arbitrary sweep rates can be useful for com-
4. Divide the amplitude of the reference signal (volts)
by the product of the vertical deflection established in step
2 (divisions) and the setting of the VOLTS/DIV switch.
This is the vertical conversion factor.
reference signal
Vertical amplitude (volts)
Conversion=-----------------------------------
Factor vertical VOLTS/DIV
deflection X switch
(divisions) setting
5. To measure the amplitude of an unknown signal,
disconnect the reference signal and connectthe unknown
signal to the selected channel input connector. Set the
VOLTS/DIV switch to a setting that provides sufficient
vertical deflection to make an accurate measurement. Do
not readjust the VAR control.
2 -1 2
REV A MAY 1980