Änderungen vorbehalten / Subject to change without notice
7
Test principle
The built-in frequency generator provides a
sinusoidal voltage at the same frequency as the line
voltage, which is then applied to the series circuit
consisting of the test object and a built-in switchable
resistor.
In the case of resistors or other non-complex
components, the 2 deflection voltages are in phase
and a snore or less diagonal line will appear on the
oscilloscope screen.
If the test cables are shorted,
a vertical llins is displayed.
If the leads are open, a
horizontal line will result. Capacitors and inductors
cause a phase difference between current and voltage,
and thus between the 2 deflection voltages. The result
is ellipsoidal traces.
The slope and width of the
ellipses are indicative of the impedance.
In the case of semiconductors,
a voltage-induced
sharp change in direction in the curve
can be
observed at the transition point from the conductive
to the nonconductive state. To the extent permitted
by the applied test voltage, the
forward and reverse
characteristics
of semiconductor components are
displayed (e.g. for a zener diode below 12V, etc.). Only
2-point measurements can be performed; for this
reason, transistor gain and the like cannot be
measured with the HZ65.
Since only a few volts are applied to the test
object, non-destructive testing is possible of the
individual zones of almost all semiconductors.
Direct in-circuit testing
is possible in rnany
cases, however, parallel circuits with other, complex
components can cause significant changes in the
curve traces. Nevertheless, with a certain amount of
experience or by comparing with the traces of known
functional circuits, faulty components can be quickly
identified. In cases of doubt, one of the component
leads can be desoldered.
Carry out tests with the HZ 65 only in circuits in
which no currents are flowing (otherwise there
is a risk of damage to the circuit and the tester).
Oscilloscope types
The HZ 65 can be connected to any oscilloscope with
X and Y inputs (in X-Y mode or external X deflection).
Testing
Individual components with thin leads can be
tested most quickly out-of-circuit by plugging them
into one of the 2
socket contacts
for testing. The
included test cables can be connected to the HZ 65
for in-circuit testing of components or testing of
components with leads that will riot fit into the
sockets. Use the lower slide switch (current) to adjust
the
test current.
The recommended settings are as
follows:
Diodes, small-signal trans., FETs.:
Medium
Thyristors, triacs:
Maximum
Resistors up to 5k
Ω
:
Minimum
Up to 500
Ω
:
Medium
Up to 50
Ω
:
Maximum
Unpolarized capacitors up to 1µF:
Minimum
Up to 10µF:
Medium
Over 10µF:
Maximum
Fuse: T 100mA for 115 V
The line overcurrent protection device must have a
rating which corresponds to the selected line voltage,
and must therefore be replaced when changing over.
For type information, consult the circuit diagram.
Once you have made sure that the line voltage and
overcurrent protection device correspond arid the
enclosure has been closed, the 2 BNC jacks rnay be
connected to the oscilloscope using the corresponding
BNC cables:
X (voltage) = Horizontal input
Y (current) = Vertical input
It the oscilloscope has a different jack type, the
BNC jacks can be connected using apropriate
adaptors. For connecting the component tester to
the oscilloscope, BNC-BNC cables such as HZ31,
HZ33, and HZ34, also supplied by HAMEG, are
suitable. For oscilloscopes equipped with banana
jacks, the connection cable HZ32 8NC may be used
with 4-mm banana plugs.
If you construct your own adaptor, make sure that
the frames of the BNC jacks of the HZ65 are also
connected with the oscilloscope chassis for grounding
purposes. Consult the operating instructions for the
oscilloscope, and set it to X-Y mode or external X
deflection, as well as - if possible- DC input coupling.
After the component tester and oscilloscope have
been powered up, a horizontal baseline should appear
in the oscilloscope screen. Use the Horizontal control
to adjust the length of the base-line
to approx. half
of screen width.
If the 2 banana jacks of the HZ65 are shorted, a
vertical line appears on the oscilloscope screen. Use
the Y time-division control of the oscilloscope to adjust
its length to about
half of screen height.
The HZ65 is now ready for operation. It is a good
idea to make a note of the oscilloscope settings so
that quick tests can be performed with the HZ65 in
the middle of other tasks.
Avoid operating the HZ65 for lengthy periods of
time with shorted inputs and maximum current. I t is
advisable to set the
current switch
of the HZ65
to
minimum level after each test.
This prevents any
damage from occurring if the 2 test cables should
accidentally be shorted on the test bench.
isolated wires
