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However, these three values are not freely selectable. They
have to be within the following limits (trigger threshold,
accuracy of reading):
H
between 0.5 and 8div., if possible 3.2 to 8div.,
U
between 1 mVpp and 40Vpp,
D
between 1 mV/div. and 5V/div. in 1-2-5 sequence.
Examples:
Set deflection coefficient
D
= 50mV/div. ^ 0.05 V/div.,
observed display height
H
= 4.6 div.,
required voltage U
= 0.05 -4.6 =
0.23 Vpp.
Input voltage
U =
5Vpp,
set deflection coefficient
D
= 1 V/div.,
required display height H
= 5:1 =
5div.
Signal voltage U = 220\/,^,-2-VY = 622 Vpp
(voltage > 40Vpp, with probe x 100:
U
= 6.22 Vpp),
desired display height
H
= min. 3.2div., max. 8div.,
max. deflection coefficient D = 6.22:3.2 = 1.94V/div.,
min. deflection coefficient D = 6.22:8 = 0.78V/div.,
adjusted deflection coefficient D = 1 V/div.
If the applied signal is superimposed on a DC (direct
voltage) level the total value (DC + peak value of the
alternating voltage) of the signal across the Y-input
must not exceed ±400V (see figure). This same limit
applies to normal xIO attenuator probes, the attenuation
ratio of which allows signal voltages up to approximately
400Vpp to be evaluated. Voltages of up to approximately
2,400Vpp may be measured by using the HZ53 high voltage
probe which has an attenuation ratio of 100:1. It should be
noted that its ACpeak value is derated at higher frequencies.
If a normal xIO probe is used to measure high voltages
there is the risk that the compensation trimmer bridging the
attenuator series resistor will break down causing damage
to the input of the oscilloscope. However, if for example
only the residual ripple of a high voltage is to be displayed on
the oscilloscope, a normal xIO probe is sufficient. In this
case, an appropriate high voltage capacitor (approx. 22-
68 nF) must be connected in series with the input tip of the
probe.
Voltage
Total value of input voltage
The dotted line shows a voltage alternating at zero volt level. When superim¬
posed a DC level, the addition of the positive peak and the DC voltage results
in the max. voltage (DC -i- ACpeaJ.
It is very important that the oscilloscope input coupling is
set to
DC,
if an attenuator probe is used for voltages higher
than 400V (see page IVI6: Connection of Test Signal).
With
Y-POS.
control (input coupling to
GD)
it is possible to
set a horizontal graticule line as reference line for ground
potential before the measurement. It can lie below or
above the horizontal central line according to whether posi¬
tive and/or negative deviations from the ground poterntial
are to be measured. Certain switchable xIO/xl attenuator
probes also have a built-in ground reference switch posi¬
tion.
Time Measurements
As a rule, most signals to be displayed are periodically
repeating processes, also called periods. The number of
periods per second is the repetition frequency. Depending
on the time base setting of the TIME/DIV. switch, one or
several signal periods or only a part of a period can be dis¬
played. The time coefficients are stated in
ms/div.
and \>s/
div.
on the TIME/DIV.-switch. The scale is accordingly
divided into two fields.
The duration of a signal period or a part of it is deter¬
mined by multipiying the reievant time (horizontal dis¬
tance in div.) by the time coefficient set on the TIME/
DlM.-switch.
The variabie time control (identified with an arrow
knob cap) must be in its caiibrated position CAL. (arrow
pointing horizontally to the right).
With the designations
L = displayed wave
length in div.
of one period,
T =
time In seconds
for one period,
F = recurrence
frequency in Hz
of the signal,
Tc = time coefficient in s/div.
on timebase switch and
the relation F = 1 /T, the following equations can be stated;
F - , 1_
L - .1
T
-
^
L'Tc
F-Tc
LF
With depressed
X-MAG. x10
pushbutton the Tg
value
must be divided by 10.
However, these four values are not freely selectable. They
have to be within the following limits:
L between 0.2 and lOdiv., if possible 4 to lOdiv.,
T
between 0.02 [xs and 1 s,
F between 0.5 Hz and 20 MHz,
Tc between 0.2[is/div. and 0.1 s/div. in 1-2-5 sequence
(with
X-MAG. xIO
in out position), and
Tc between 20ns/div. and 10 ms/div. in 1-2-5 sequence
(with pushed
X-MAG. x 10
pushbutton).
M4 203-7
Subject to change without notice
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