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Automatic Peak (value) - Triggering

If the 

AT/NM

 pushbutton is in the out position 

AT

, the sweep

generator is running without test signal or external trigger voltage.
A base line is always displayed even without a signal applied.

In automatic trigger mode the sweep generator can run without
test signal or external trigger voltage. A base line will always be
displayed even with no signal. With an applied 

AC

 signal the

peak value triggering enables the user to select the voltage
point on the trigger signal (trigger point), by the adjustment of
the trigger 

LEVEL 

control. The control range depends on the

peak to peak value of the signal. This trigger mode is therefore
called 

Automatic Peak (Value)- Triggering

. Operation of the

scope needs only correct amplitude and time base settings, for
a constantly visible trace. Automatic mode is recommended for
all uncomplicated measuring tasks. However, automatic
triggering is also the appropriate operation mode for the “entry”
into difficult measuring problems, e.g. when the test signal is
unknown relating to amplitude, frequency or shape. Presenting
of all parameters is now possible with automatic triggering; the
change to normal triggering can follow thereafter.

The automatic triggering works above 20Hz. The failure of
automatic triggering at frequencies below 20Hz is abrupt.
However, it is not signified by the trigger indicator LED this is still
blinking. Break down of triggering is best recognizable at the left
screen edge (the start of the trace in differing display height).

The automatic peak (value) triggering operates over all variations
or fluctuations of the test signal above 20Hz. However, if the
pulse duty factor of a square-wave signal exceeds a ratio of
100:1, switching over to normal triggering will be necessary.
Automatic triggering is practicable with internal and external
trigger voltage.

Normal Triggering

With normal triggering (

AT/NM

 button depressed) the sweep

can be started by 

AC

 signals within the frequency range

defined by the 

TRIG. MODE 

(trigger

 

coupling) setting.

In the absence of an adequate trigger signal or when the trigger
controls (particularly the LEVEL control) are misadjusted, no
trace is visible, i.e. the screen blanked completely.

When using the internal normal triggering mode, it is possible
to trigger at any amplitude point of a signal edge, even with very
complex signal shapes, by adjusting the 

LEVEL

 control. Its

adjusting range is directly dependent on the display height,
which should be at least 

0.5div.

 If it is smaller than 1div., the

LEVEL

 adjustment needs to be operated with a sensitive

touch. In the external normal triggering mode, the same applies
to approx. 0.3Vpp external trigger voltage amplitude.

Other measures for triggering of very complex signals are the
use of the time base variable control and 

HOLDOFF

 time control,

hereinafter mentioned.

Slope  

The time base generator can be started by a rising or falling edge
of the test signal. This is valid with automatic and with normal
triggering. The selected slope is set with the 

SLOPE ( 

 

)

pushbutton. The 

/

 sign (button released) means an edge, which

is coming from a negative potential and rising to a positive
potential. That has nothing to do with zero or ground potential
and absolute voltage values. The positive slope may also lie in a
negative part of a signal. A falling edge ( 

\

 sign) triggers, when the

SLOPE (

 

)

 pushbutton is depressed.

However the trigger point may be varied within certain limits on
the chosen edge using the 

LEVEL

 control. The slope direction is

always related to the input signal and the non inverted display.
.

Trigger coupling

The coupling mode and accordingly the frequency range of the
trigger signal can be changed using the 

TRIG.

 

MODE 

selector

switch.

AC:

Trigger range 

<20Hz to 100MHz

.

This is the most frequently used trigger mode. The trigger
threshold is increasing below 20Hz and above 100MHz.

DC:

Trigger range 

DC to 100MHz

.

DC triggering is recommended, if the signal is to be triggered
with quite slow processes or if pulse signals with constantly
changing pulse duty factors have to be displayed.

With DC- or LF-trigger coupling, always work with normal
triggering and LEVEL adjustment.

LF:

Trigger range 

DC to 1.5kHz

 (low-pass filter).

The LF position is often more suited for low-frequency
signals than the DC position, because the (white) noise in
the trigger voltage is strongly suppressed. So jitter or
double-triggering of complex signals is avoidable or at least
reduced, in particular with very low input voltages. The
trigger threshold increases above 1.5kHz.

TV:

The built-in 

active TV-Sync-Separator

 enables the

separation of sync pulses from the video signal. Even
distorted video signals are triggered and displayed in a
stable manner.

Video signals are triggered in the automatic mode. The
internal triggering is virtually independent of the display
height, but the sync pulse must exceed 0.5div. height. For
TV sync pulse separation the 

TRIG. MODE

 switch must be

set to 

TV

. The 

TIME/DIV

.-switch selects between 

field

(

0.2s/div. - 1ms/div

.) and 

line

 (

0.5ms/div. - 0.1µs/div.

).

The slope of the leading edge of the synchronization pulse is
critical for the 

SLOPE

 pushbutton setting. If the displayed sync

pulses are 

above

 the picture (field) contents, then the

 SLOPE

pushbutton ( 

) must be in 

/

 position (out). In the case of sync

pulses

 below

 the field/line, the leading edge is negative and the

SLOPE 

pushbutton must therefore be depressed (to ”

\

”). Since

the 

INV. 

(invert) function may cause a misleading display, it must

not be activated until after correct triggering is achieved.
On the 2ms/div setting field TV triggering is selected and 1 field
is visible if a 50 fields/s signal is applied. If the holdoff control is
in fully ccw position, it triggers without line interlacing affects
caused by the consecutive field. More details in the video signal
become visible if the 

X-MAG. x10

 pushbutton is depressed (in).

The 

X-POS

. control allows to display any part of the expanded

signal. The influence of the integrating network which forms a
trigger pulse from the vertical sync pulses may become visible
under certain conditions.

Disconnecting the trigger circuit (e.g. by rapidly pressing and
releasing the 

TRIG. EXT.

 button) can result in triggering the

consecutive (

odd

 or 

even

) field.

On the 10µs/div setting line TV triggering is selected and approx.
1

½ 

 lines are visible. Those lines originate randomly from the odd

and even fields.

The sync-separator-circuit also operates with external triggering.
It is important that the voltage range (0.3V

pp

 to 3V

pp

) for external

Triggering and time base

Summary of Contents for HM303-6

Page 1: ...O s c i l l o s c o p e H M 3 0 3 6 Manual English...

Page 2: ...lifiers 12 X Y Operation 13 Phase comparison with Lissajous figures 13 Phase difference measurement 13 in DUAL mode 13 Phase difference measurement in DUAL mode 14 Measurement of an amplitude modulati...

Page 3: ...effected by such fields Although the interior of the oscilloscope is screened by the cabinet direct radiation can occur via the CRT gap As the bandwidth of each amplifier stage is higher than the tot...

Page 4: ...oise Amplifiers Time Base 0 2 s 100 ns cm with X Magnification to 10 ns cm Triggering from 0 to 50 MHz from 5 mm signal level 100 MHz 8 mm Analog mode provides unexcelled signal presentation at high r...

Page 5: ...1 s div 1 2 5 Sequence Accuracy 3 Variabel uncalibrated 2 5 1 to 0 5 s div X Magnification x 10 up to 10 ns div Accuracy 5 Hold Off Time variable to approx 10 1 XY Bandwidth X Amplifier 0 2 5 MHz 3 d...

Page 6: ...Without pulling the locking knobs they will latch in into the next locking position Handle mounting dismounting The handle can be removed by pulling it out further depending on the instrument model in...

Page 7: ...e atmosphere or if there is danger of explosion The operating position may be any however sufficient ventilation mustbeensured convectioncooling Prolongedoperationrequires the horizontal or inclined p...

Page 8: ...83 times the potential difference in Vpp The relationship between the different voltage magnitudes can be seen from the following figure Voltage values of a sine curve Vrms effective value Vp simple p...

Page 9: ...frequency Depending on the time base setting of the TIME DIV switch one or several signal periods or only a part of a period can be displayed The time coefficients are stated in s div ms div and s div...

Page 10: ...d The attenuator switch must then be turned back to the left until the vertical signal height is only 3 8div With a signal amplitude greater than 160Vpp an attenuator probe must be inserted before the...

Page 11: ...be visible after a short warm up period of approx 10 seconds Adjust Y POS I and X POS controls to center the baseline Adjust INTENS intensity and FOCUS controls for medium brightness and optimum sharp...

Page 12: ...is slightly more difficult but causes a better result The rising edge should be as steep as possible with a pulse top remaining as straight and horizontal as possible After completion of the HF adjus...

Page 13: ...uite simple with the following formula and a pocket calculator with trigonometric functions Apart from the reading accuracy the signal height has no influence on the result The following must be noted...

Page 14: ...tion F 1 MHz f 1 kHz m 50 UT 28 3 mVrms If the two values a and b are read from the screen the modulation factor is calculated from where a UT 1 m and b UT 1 m The variable controls for amplitude and...

Page 15: ...a positive potential That has nothing to do with zero or ground potential and absolute voltage values The positive slope may also lie in a negative part of a signal A falling edge sign triggers when...

Page 16: ...ossible in this trigger mode External triggering The internal triggering is disconnected by depressing the TRIG EXT button The time base can be triggered externally via the TRIG EXT socket using a 0 3...

Page 17: ...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 After use to retu...

Page 18: ...can be identified by comparison with a known diode Testing Transistors Three different tests can be made to transistors base emitter base collector and emitter collector The resulting test patterns ar...

Page 19: ...soldered This terminal should then be connected to the insulated COMP TESTER socket avoiding hum distortion of the test pattern Another way is a test pattern comparison to an identical circuit which i...

Page 20: ...II display SLOPE Selects the slope of the trigger signal Element Function SLOPE rising edge pushbutton switch falling edge TR LED lights if sweep is triggered LED LEVEL Adjustment of trigger level kno...

Page 21: ...ast 2 5 fold For time measurements turn to right hand stop Element Function XY Selects X Y operation pushbutton switch stops sweep X signal via CH I Attention Phosphor burn in without signal TRIG EXT...

Page 22: ...ggering TRIG EXT pushbutton depressed sync signal 0 3Vpp to 3Vpp to TRIG EXT socket Line triggering normal triggering AT NM and ALT pushbuttons depressed Select trigger coupling with TRIG MODE selecto...

Page 23: ...M A N U A L H A N D B U C H M A N U E L...

Page 24: ...stra e 6 A Rohde Schwarz Company D 63533 Mainhausen registrierte Marke Tel 49 0 61 82 800 0 DQS Zerti kation DIN EN ISO 9001 2000 Fax 49 0 61 82 800 100 Reg Nr 071040 QM sales hameg de Oscilloscopes S...

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