Subject to change without notice
10
required period T = 7x100x10-9 = 0.7µs
required rec. freq. F = 1:(0.7x10-6) = 1.428MHz.
Signal period T = 1s,
set time coefficient Tc = 0.2s/div,
required wavelength L = 1:0.2 = 5div.
Displayed ripple wavelength L = 1div,
set time coefficient Tc = 10ms/div,
required ripple freq. F = 1:(1x10x10-3) = 100Hz.
TV-Line frequency F = 15625Hz,
set time coefficient Tc = 10µs/div,
required wavelength L = 1:(15 625x10-5) = 6.4div.
Sine wavelength L = min. 4div, max. 10div,
Frequency F = 1kHz,
max. time coefficient Tc = 1:(4x103) = 0.25ms/div,
min. time coefficient Tc = 1:(10x103) = 0.1ms/div,
set time coefficient Tc = 0.2ms/div,
required wavelength L = 1:(103x0.2x10-3) = 5div.
Displayed wavelength L = 0.8div,
set time coefficient Tc = 0.5µs/div,
pressed X-MAG. (x10) button: Tc = 0.05µs/div,
required rec. freq. F = 1:(0.8x0.05x10-6) = 25MHz,
required period T = 1:(25x106) = 40ns.
If the time is relatively short as compared with the complete
signal period, an expanded time scale should always be applied
(X-MAG. (x10) active). In this case, the time interval of interest
can be shifted to the screen center using the X-POS. control.
When investigating pulse or square waveforms, the critical feature
is the rise time of the voltage step. To ensure that transients,
ramp-offs, and bandwidth limits do not unduly influence the
measuring accuracy, the rise time is generally measured between
10% and 90% of the vertical pulse height. For measurement,
adjust the Y deflection coefficient using its variable function
(uncalibrated) together with the Y-POS. control so that the pulse
height is precisely aligned with the 0% and 100% lines of the
internal graticule. The 10% and 90% points of the signal will now
coincide with the 10% and 90% graticule lines. The rise time is
given by the product of the horizontal distance in div between
these two coincident points and the calibrated time coefficient
setting. The fall time of a pulse can also be measured by using
this method.
With a time coefficient of 2ns/div (X x10 magnification active),
the example shown in the above figure results in a total measured
rise time of
t
tot
= 1.6div x 2ns/div =
3.2ns
When very fast rise times are being measured, the rise times of
the oscilloscope amplifier and of the attenuator probe has to be
deducted from the measured time value. The rise time of the
signal can be calculated using the following formula.
t
r
=
√
t
tot
2
- t
osc
2
- t
p
2
In this t
tot
is the total measured rise time, t
osc
is the rise time of
the oscilloscope amplifier (HM2005 approx. 1.75ns), and t
p
the
rise time of the probe (e.g. = 1.4ns). If t
tot
is greater than 16ns,
then t
tot
can be taken as the rise time of the pulse, and calculation
is unnecessary.
Calculation of the example in the figure above results in a signal
rise time
t
r
=
√
3.2
2
– 1.75
2
– 1.4
2
= 2.28ns
The measurement of the rise or fall time is not limited to the
trace dimensions shown in the above diagram. It is only
particularly simple in this way. In principle it is possible to measure
in any display position and at any signal amplitude. It is only
important that the full height of the signal edge of interest is
visible in its full length at not too great steepness and that the
horizontal distance at 10% and 90% of the amplitude is measured.
If the edge shows rounding or overshooting, the 100% should
not be related to the peak values but to the mean pulse heights.
Breaks or peaks (glitches) next to the edge are also not taken
into account. With very severe transient distortions, the rise and
fall time measurement has little meaning. For amplifiers with
approximately constant group delay (therefore good pulse
transmission performance) the following numerical relationship
between rise time
tr (in ns)
and bandwidth
B (in MHz)
applies:
Connection of Test Signal
In most cases briefly depressing the
AUTOSET
causes a useful
signal related instrument setting. The following explanations refer
to special applications and/or signals, demanding a manual
instrument setting.
The description of the controls is explained
in the section “Controls and Readout”
.
Caution:
When connecting unknown signals to the oscilloscope
input, always use automatic triggering and set the input
coupling switch to AC (readout). The attenuator should
initially be set to 5V/div.
Sometimes the trace will disappear after an input signal has been
applied. Then a higher deflection coefficient (lower input
sensitivity) must be chosen until the vertical signal height is only
3-8div. With a signal amplitude greater than 40Vpp and the
deflection coefficient
(VOLTS/DIV.)
in calibrated condition, an
attenuator probe must be inserted before the vertical input. If,
after applying the signal, the trace is nearly blanked, the period
of the signal is probably substantially longer than the set time
deflection coefficient (
TIME/DIV.
). It should be switched to an
adequately larger time coefficient.
The signal to be displayed can be connected directly to the Y-
input of the oscilloscope with a shielded test cable such as
HZ32
or
HZ34
, or reduced through a x10 or x100 attenuator probe. The
use of test cables with high impedance circuits is only
recommended for relatively low frequencies (up to approx. 50kHz).
Basics of signal voltage
