19
Subject to change without notice
AUTOSET
For specific information consult ”Controls and Readout“
AUTOSET
11
.
The following description is valid for both analog and digital
mode. AUTOSET does not change from analog to digital mode
or vice versa. If in digital mode the modes ”Roll“, ”Envelope“ or
”Average“ (ACQUIRE) are present or the trigger mode „Single“
(MODE) is selected, theses modes will be switched off as AU-
TOSET always switches to ”Refresh“ acquistion. The signal to
be displayed must meet the amplitude and frequency require-
ments of automatic triggering, to enable a useful automatic
instrument setting.
All controls except for the POWER switch are electronically
scanned, all functions can also be controlled by the microcom-
puter, i.e. also via the interfaces.
This is a precondition for AUTOSET as this function must be able
to control all functions independent of control settings. With the
exception of FFT, AUTOSET will always switch to YT mode, but
preserve the previous selection of CH1, CH2 or dual trace; ADD
or XY modes will be switched to dual trace Yt.
AUTOSET helps in combination with FFT to avoid scaling pro-
blems and ensures that the signal height is within A/D converter
limits.
Automatic setting of the vertical sensitivities and the time base
will present a display within 6 cm height (4 cm per signal in dual
trace) and about 2 signal periods. This is true for signals not
differing too much from a 1:1 duty cycle. For signals containing
several frequencies like video signals the display may vary.
Initiating the AUTOSET function will set the following operating
conditions:
– last selection of ac or DC coupling
– internal
triggering
– automatic
triggering
– automatic trigger source selection
– trigger level set to the center of its range
– calibrated
Y
sensitivities
– calibrated
time
base
– AC or DC trigger coupling unmodifi ed
– HF trigger coupling switched to DC
– LF or Noise Reject fi lters left
– X
magnifi er switched off
– Y and X positioning automatic
Please note:
For pulse signals with duty cycles approaching 400:1 no au-
tomatic signal display will be possible.
In such cases switch to normal trigger mode and set the trigger
position about 5 mm above the centre. If the trigger LED lights
up, a trigger is generated and the time base is operating. In
order to obtain a visible display it may be necessary to change
the time base and V/DIV settings. Depending on the duty cycle
and the frequency, the signal may still remain invisible. This
applies only to analog mode. In digital mode the trace is always
of equal brightness because not the actual signal is shown,
but a low frequency construction of it. Also there is no stored
information about the trace intensity.
C o m p o n e n t T e s t e r
Component Tester
Specifi c information can be found in ”Controls and Readout“ un-
der COMPONENT/PROBE
40
and COMPONENT TESTER
41
.
The scope has a built in component tester. The test object is con-
nected with 4 mm banana plugs. In this mode the Y amplifiers
and the time base are turned off. If the components are part of a
circuit this must be de energized and disconnected from safety
ground. Except for the two test leads there must be no further
connection between scope and component. (See ”Tests within a
circuit“). As described in section ”Safety“ all ground connections
of the scope are connected to safety ground including those of
the component tester. As long as individual components are
tested this is of no consequence.
The display can only be affected by the controls contained in
the FOCUS/TRACE menu: A-Int., Focus, Trace rotation, HORI-
ZONTAL position.
If components are to be tested which are part of a circuit or
an instrument they must first be de energized. If they are con-
nected to the mains they must be unplugged. This will prevent
a connection between scope and circuit via the safety ground
which may affect the measurement.
STOP
Do not test charged capacitors.
The principle of the test is very simple: a sine wave generator
within the scope generates a 50 Hz ±10 % voltage which is
applied to a series connection of the test object and a resistor
within the scope. The sine wave proper deflects in X direction,
the voltage across the resistor which is proportional to the test
current deflects in Y direction.
If the object contains neither capacitors nor inductors, there will
be no phase shift between voltage and current, so a straight
line will show up which will be more or less slanted, depending
on the value of the object’s resistance, covering approx. 20 Ω
to 4.7 kΩ. If there is a short circuit, the trace will be vertical,
i.e. (almost) no voltage produces a high current. A horizontal
line will thus indicate an open circuit: there is only voltage but
no current.
Capacitors or inductors will create ellipses. The impedance
may be calculated from the ellipse’s geometric dimensions.
Capacitors of approx. 0.1 μF to 1000 μF will be indicated.
– An ellipse with its longer axis horizontal indicates a high
impedance (low capacitance or high inductance)
– An ellipse with its longer axis vertical will indicate a low
impedance (high capacitance or low inductance)
– A slanted ellipse will indicate a lossy capacitor or inductor.
Semiconductors will show their diode characteristics, however,
only 20 Vpp are available, so the forward and reverse characte-
ristics can only be displayed up to 10 Vp in each direction. The
test is a two terminal test, hence it is not possible to measure
e.g. the current gain of a transistor. One can only test B-C, B-E,
and C-E. The test current is only a few mA, so the test will not
harm ordinary semiconductors. (Sensitive devices like delicate
hf transistors etc. should not be tested). The limitation to 10 Vp
with bipolar transistors will usually suffice as common defects
will show up.The best method to verify whether a component
is defective is comparison to a good one. If the lettering of a
