Hameg HM 1004-3 Series, Руководство пользователя

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Subject to change without notice
Component Tester
selected by AUTO SET as the bandwidth is reduced on these
settings.
Attention!
If a signal is applied with a pulse duty factor of approx.
400:1 or larger, an automatic signal display cannot be
performed. The pulse duty factor causes too low a Y
deflection coefficient (sensitivity too high) and too
high a time deflection coefficient (timebase speed too
slow) and results in a display in which only the base-
line is visible.
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 re-
duced. Please note that a reduction in intensity may occur,
which could result in a blank screen when the physical limits
are reached.
Component Tester
General
The instrument specific information regarding the control and
terminals are part of
item (40) 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 transis-
tors), 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 timebase generator are inoperative. A
shortened horizontal trace will be observed. It is not neces-
sary to disconnect scope input cables unless in-circuit meas-
urements are to be carried out. For the component connec-
tion, 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 “Con-
trols and Readout ”.
Test Procedure
Caution!
Do not test any component in live circuitry - remove all
grounds, power and signals connected to the compo-
nent under test. Set up Component Tester as stated.
Connect test leads across component to be tested.
Observe oscilloscope display.
Only discharged capacitors should be tested!
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, giving an ellipse-shaped display. The position and
opening width of the ellipse will vary according to the imped-
ance value (at 50Hz) of the component under test.
A horizontal ellipse indicates a high impedance or a relatively
small capacitance or a relatively high inductance.
A vertical ellipse indicates a small impedance or a relatively
large capacitance or a relatively small inductance.
A sloping ellipse means that the component has a consider-
able ohmic resistance in addition to its reactance.
The values of capacitance of normal or electrolytic capacitors
from 0.1µF to 1000µF can be displayed and approximate
values obtained. More precise measurement can be obtained
in a smaller range by comparing the capacitor under test with
a capacitor of known value. Inductive components (coils,
transformers) can also be tested. The determination of the
value of inductance needs some experience, because inductors
have usually a higher ohmic series resistance. However, the
impedance value (at 50Hz) of an inductor in the range from 20
Ohm to 4.7k
Ω
can easily be obtained or compared.
Testing Semiconductors
Most semiconductor devices, such as diodes, Z-diodes, tran-
sistors, FETs can be tested. The test pattern displays vary
according to the component type as shown in the figures
below. The main characteristic displayed during semiconduc-
tor testing is the voltage dependent knee caused by the
junction changing from the conducting state to the non
conducting state. It should be noted that both the forward and
the reverse characteristic are displayed simultaneously. This