Subject to change without notice
30
In such cases it is recommended to select normal triggering and
to set the trigger point approx. 0.5div above or below the trace.
If under one of these conditions the trigger indicator LED is lit,
this indicates the presence of a signal. Then both the time
coefficient and Y deflection coefficient should be reduced. Please
note that a reduction in intensity may occur, which could result
in a blank screen when the physical limits are reached.
Mean Value Display
The DC Mean Value of the input voltage is displayed in place of
the CURSOR line measurement, if the CURSOR measurement
function is not activated. MEAN VALUE
ON
must activated under
MISCELLANEOUS (submenu of SETUP) and further conditions
met.
The signal to be measured (AC > 20 Hz) must be applied at input
CH I or CH II with its DC content at the input (i.e. DC coupling
required). Yt (time base) mode and internal triggering (trigger
source CH I or CH II; not alternated triggering) must be used. AC
or DC trigger coupling must be selected. If the above conditions
are not met, “DC:?” will be displayed.
The mean value is acquired using the internal trigger signal
amplifiers. With the exception of DUAL mode, the indicated mean
value is automatically related to the active channel (CH I or CH
II), as the channel selection also selects the assigned trigger
amplifier. In DUAL mode one can select between trigger amplifier
CH I or CH II for triggering. Thus the indicated mean value refers
to the channel from which the trigger signal originates.
The DC mean value is displayed with an algebraic sign (e.g. “DC:
501mV” or “DC: -501mV). Overranging is indicated by “ < “ or “
> “ sign (e.g. “DC<1.80V” or “DC>1.80V”). Being dependent on
a necessary time constant for mean value creation, the display
update requires a few seconds after a voltage change.
The reading accuracy is dependent on the instrument
specifications (vertical deflection tolerance max. 3% from 5mV/
div. to 20V/div.). Although the tolerances are significantly smaller
in reality, other deviations such as unavoidable offset voltages
must be taken into account, which may cause a display deviating
from 0 Volt without signal applied at the input.
The display shows the arithmetic (linear) mean value. The DC
content is displayed if DC or DC with superimposed AC voltages
are applied. In the case of square wave voltages, the mean value
depends on the pulse duty factor.
Component Tester
General
The instrument specific information regarding the control and
terminals are part of
item (42)
in section
“Controls and Readout”
.
The instrument has a built-in electronic Component Tester, which
is used for instant display of a test pattern to indicate whether or
not components are faulty. It can be used for quick checks of
semiconductors (e.g. diodes and transistors), resistors,
capacitors, and inductors. Certain tests can also be made to
integrated circuits. All these components can be tested
individually, or in circuit provided that it is unpowered. The test
principle is fascinatingly simple. A built-in generator delivers a
sine voltage, which is applied across the component under test
and a built-in fixed resistor. The sine voltage across the test object
is used for the horizontal deflection, and the voltage drop across
the resistor (i.e. current through test object) is used for vertical
deflection of the oscilloscope. The test pattern shows a current-
voltage characteristic of the test object.
The measurement range of the component tester is limited and
depends on the maximum test voltage and current (please note
data sheet). The impedance of the component under test is limited
to a range from approx. 20
Ω
to 4.7k
Ω
. Below and above these
values, the test pattern shows only short-circuit or open-circuit.
For the interpretation of the displayed test pattern, these limits
should always be born in mind. However, most electronic
components can normally be tested without any restriction.
Using the Component Tester
After the component tester is switched on, the vertical
preamplifier and the time base generator are inoperative. A
shortened horizontal trace will be observed. It is not necessary
to disconnect scope input cables unless in-circuit measurements
are to be carried out. For the component connection, two simple
test leads with 4mm Ø banana plugs, and with test prod, alligator
clip or sprung hook, are required.
The test leads are connected as described in section
“Controls
and Readout
”.
Caution!
Do not test any component in live circuitry. Remove all
grounds, power and signals connected to the component
under test. Set up Component Tester as stated. Connect
test leads across component to be tested. Observe oscil-
loscope display.
IMPORTANT: Only discharged capacitors should be testet!
Test Pattern Displays
The “Test patterns” shows typical patterns displayed by the
various components under test.
Open circuit is indicated by a straight horizontal line.
Short circuit is shown by a straight vertical line.
Testing Resistors
If the test object has a linear ohmic resistance, both deflecting
voltages are in the same phase. The test pattern expected from
a resistor is therefore a sloping straight line. The angle of slope is
determined by the resistance of the resistor under test.
With high values of resistance, the slope will tend towards the
horizontal axis, and with low values, the slope will move towards
the vertical axis. Values of resistance from 20
Ω
to 4.7k
Ω
can be
approximately evaluated. The determination of actual values will
come with experience, or by direct comparison with a component
of a known value.
Testing Capacitors and Inductors
Capacitors and inductors cause a phase difference between
current and voltage, and therefore between the X and Y deflection,
Mean Value Display
