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Subject to change without notice
D o c u m e n t a t i o n , s t o r i n g a n d r e c a l l i n g
11 Component test
11.1 General
The oscilloscopes HMO72x...HMO202x have a built-in
compo
-
nent tester. This can be activated by pushing the XY/CT mode
button and switch on CT at the upcoming menu at the top. The
unit under test is connected to the two contacts below the
screen. After switch on the
component tester moder, the Y
preamplifiers and the
time base are disconnected. While using
the
component tester, signals may be present at the inputs as
long as the unit under test is not connected to any other circuit.
It is possible to test components remaining in their circuits,
but in such cases all signals must be disconnected from the
front panel BNC connectors! (See the following paragraph:
„Test in circuits“). Two cables with 4 mm plugs are necessary
to connect the unit under test to the component tester. After
completion of the component test pushing the lower soft key
COMP. TEST OFF leave the component tester mode and resume
normal scope operation.
As outlined in the chapter Safety, all measurement
connectors are connected to the mains safety
earth (in proper operation). This implies also the
COMP.TESTER contacts. As long as individual
components are tested, this is of no consequence
because these components are not connected to
the mains safety earth.
If components are to be tested which are located
in circuits or instruments, these circuits resp.
instruments must be disconnected first under
all circumstances! If they are operated from the
mains, the mains plug of the test object has to be
pulled out. This ensures that there will be no loops
between the scope and the test object via the safe-
ty earth which might cause false results.
Only discharged capacitors may be tested!
The test principle is a generator within the HMO generates
a 50 Hz or 200 Hz (±10 %) sine wave which feeds the series
connection of the test object and a sense resistor.
If the test object has only a real part such as a resistor, both
voltages will be in phase; the display will be a straight line,
more or less slanted. Is the test object short-circuited, the
line will be vertical (no voltage, current maximum). If the
test object is open-circuited or missing a horizontal line will
appear (voltage, but no current). The angle of the line with the
horizontal is a measure of the resistance value, allowing for
measurements of resistors between Ω and kΩ.
Capacitors and inductors cause phase shift between voltage
and current and hence between the voltages. This will cause
displays of ellipses. The location and the form factor of the
ellipse are determined by the apparent impedance at 50 Hz
(resp. 200 Hz). Capacitors can be measured between µF and
mF.
– An ellipse with its longer axis horizontal indicates a high
impedance (small capacitance or large inductance)
– An ellipse with its longer axis vertical indicates a low im
-
pedance (large capacitance or small inductance)
– An ellipse with its longer axis slanted indicates a relatively
large resistive loss in series with the impedance of the
capacitor or inductor.
described in previous chapters, you must first select the
corresponding settings for storage location, name etc. The
soft menu key
FILE/PRINT
in the SAVE/RECALL main menu
opens the setup menu for the FILE/PRINT key.
You may choose from the following actions:
–
DEVICE SETTINGS
: Stores settings
–
TRACES
: Stores curves
–
SCREENSHOTS
: Stores screenshots
–
SCREEN & SETUP
: Stores screenshots and settings
-
: Prints directly to a compatible printer (Postscript,
some PCL and PCLX capable printer)
If you press the respective soft menu key to activate the re
-
quired operation, the corresponding menu will be displayed
with a blue background. Press the MENU OFF key to quit the
selection menu. If you press the
FILE/PRINT key, the selected
function will be performed.
Fig. 10.8: Definition of FILE/PRINT key
