19
Subject to change without notice
SAVE/RECALL
The instrument contains a non volatile memory in which the
actual instruments settings are stored when the instrument is
switched off. After switching on the oscilloscope and a short
internal check routine the last settings become active again.
The memory mentioned before can also be used by the
operator to save 6 different instrument settings and to recall
them. This relates to all settings with the exception off
INTENS, FOCUS, TR
(trace rotation),
DEL. POS./HOLD OFF
and the calibrator frequency pushbutton.
To
SAVE
a particular front panel set up:
Press
SAVE/RECALL
pushbutton briefly. Now the trigger
coupling scale has the function of a memory location
indicator. The memory location number is indicated on the
left side of the scale below the S/R marking. After the
SAVE/RECALL
pushbutton was briefly depressed for the
first time the S/R 1 (DC) LED will blink. The memory
location can now be chosen, selecting it by depressing
one of the NORM (up / down) pushbuttons; this causes
no change in the trigger coupling setting. SAVE the front
panel setting by depressing the
SAVE/RECALL
pushbutton
until LED stops blinking. The trigger coupling active before
starting the
SAVE/RECALL
procedure (and was saved)
then becomes active again.
To
RECALL
a front panel set up:
Press
SAVE/RECALL
pushbutton briefly. Now the trigger
coupling scale has the function of a memory location
indicator. The memory location number is indicated on the
left side of the scale below the S/R marking. After the
SAVE/RECALL
pushbutton was briefly depressed for the
first time the S/R 1
(DC)
LED will blink. The memory
location can now be chosen, selecting it by depressing
one of the
NORM
(up / down) pushbuttons; this causes
no change in the trigger coupling setting.
RECALL
the front
panel setting by depressing the
SAVE/RECALL
pushbutton
briefly. The LED will stop blinking and the selected set up
is enabled. The LED display will now show the recalled
trigger coupling mode.
The recalled operating conditions are taken over by the
instrument regardless of whether the mechanical knob
settings coincide or not. If a knob is not in its calibrated
detent (CAL), the LED stops blinking. Turning the knob
then reverts to the actual mechanical setting.
To interrupt a
SAVE
or
RECALL
procedure:
If the
SAVE/RECALL
pushbutton was depressed
inadvertently, the procedure can be interrupted by
depressing any electronic selection pushbutton with the
exception of the
SAVE/RECALL
and
NORM
pushbuttons.
Component Tester
The HM304 has a built-in electronic Component Tester
(COMP. TESTER), which is used for instant display of a test
pattern to indicate whether or not components are faulty.
The
COMP. TESTER
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 in
and out of circuit.
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.
Since this circuit operates with a frequency of 50Hz (±10%)
and a voltage of approx. 7V max. (open circuit), the indicating
range of the component tester is limited. The impedance of
the component under test is limited to a range from 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 borne
in mind. However, most electronic components can normally
be tested without any restriction.
Using the Component Tester
The instrument can be switched to component tester mode
by depressing
COMP. TESTER
pushbutton once. This is
completely independent from Yt or XY mode. In component
tester mode, only the X MAG. x10 LED may be lit if it was
previously enabled. Then the X trace length is expanded 10
fold. All other LED‘s are unlit.
The following description concerns the operation without X
MAG. x10, with a horizontal trace length of approx. 8 div.
when the component tester input‘s are not connected. The
COMP. TESTER mode can be exited by depressing the COMP.
TESTER pushbutton again, setting the instrument back to
the previous mode and settings. The COMP. TESTER mode
can be saved and recalled as mentioned under SAVE/RECALL.
In component tester mode, the vertical preamplifier and the
timebase generator 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. In the COMP. TESTER mode, the only controls which
can be operated are INTENS., FOCUS, X-POS. and X MAG.
x10. All other controls except the X MAG. x10 have no
influence on the test operation.
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 to
the insulated socket and the adjacent ground socket beneath
the screen. The component can be connected to the test
leads either way round.
Test Procedure
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 above. Connect test leads across component
to be tested. Observe oscilloscope display.
Only discharged capacitors should be tested!
Test Pattern Displays
In the following typical test patterns show various
components under test.
•
Open circuit is indicated by a straight horizontal line.
•
Short circuit is shown by a straight vertical line.
Содержание HM304
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