Hameg Instruments HM 203-6 Bedienungsanleitung Seite 21

Values of resistance from 20Q to 4.7kQ can be approxi-
mately evaluated. The determination of actual values will
come with experience, or by direct comparison with a com-
ponent 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 posi-
tion and opening width of the ellipse will vary according to
the impedance value (at 50 or 60Hz) of the component
under test.
A horizontal ellipse indicates a high impedance or a
relatively small capacitance or a relatively high induct-
ance.
A vertical ellipse indicates a small impedance or a rela-
tively large capacitance or a relatively small induct-
ance.
A sloping ellipse means that the component has a con-
siderable ohmic resistance in addition to its reactance.
The values of capacitance of normal or electrolytic
capacitors from 0.7uF to 7000uF 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. Induc-
tive 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 50 or
60 Hz) of an inductor in the range from 202 to 4.7kQ can
easily be obtained or compared.
Testing Semiconductors
Most semiconductor devices, such as diodes, Z-diodes,
transistors, 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 semiconductor
testing is the voltage dependent knee caused by the Junc-
tion changing from the conducting state to the non conduct-
ing state. It should be noted that both the forward and the
reverse characteristic are displayed simultaneously. This is
a two-terminal test, therefore testing of transistor amplifica-
tion is not possible, but testing of a single junction Is easily
and quickly possible. Since the CT test voltage applied is
only very low (max. 8.5V,,,,), all sections of most semicon-
ductors can be tested without damage. However, checking
the breakdown or reverse voltage of high voltage semicon-
ductors is not possible. More important is testing compo-
nents for open or short-circuit, which from experience is
most frequently needed.
Testing Diodes
Diodes normally show at least their knee in the forward
characteristic. This is not valid for some high voltage diode
types, because they contain a series connection of several
diodes. Possibly only a small portion of the knee is visible. Z-
diodes always show their forward knee and, up to approx.
10V, their Z-breakdown, forms a second knee in the oppo-
site direction. A Z-breakdown voltage of more than 12V can
not be displayed.
Tl
pe
Type: Normal Diode HighVoltageDiode Z-Diode12V
Terminals: Cathode-Anode Cathode-Anode Cathode-Anode
Connections: (CT-GD) (CT-GD) (CT-GD}
The polarity of an unknown diode can be identified by com-
parison with a known diode.
Testing Transistors
Three different tests can be made to transistors: base-emit-
ter, base-collector and emitter-collector. The resulting test
patterns are shown below.
The basic equivalent circuit of a transistor is a Z-diode
between base and emitter and a normal diode with reverse
polarity between base and collector in series connection.
There are three different test patterns:
i
N-P-N Transistor: | | | \
—_ — = —_— et
| |
I
Terminals: b-e b-c e-c
Connections: (CT-GD) (CT-GD)
P-N-P Transistor: | | |
Terminals: b-e b-c e-C
Connections: (CT-GD) (CT-GD) (CT-GD)
Subject to change without notice
M15 203-6