Hameg HM2005-2 User Manual Download Page 28

Page: 28 / 36

Subject to change without notice

C o n t r o l s a n d R e a d o u t

MODE

(pushbutton)

Pressing this pushbutton will open the ”Trigger“ menu, where
AUTO and NORMAL can be selected. Choosing ”Slope“ will allow
to trigger on any signal shape. For video signals select ”Video“
and press the FILTER pushbutton

in order to ﬁ nd a choice of

special trigger modes for composite video signals.
In XY mode the pushbuttons MODE

, FILTER

and SOURCE

are disabled as there is no triggering in XY mode.

16.1 Auto (trigger)

Automatic triggering (Auto) is active if the NORM display

is not

illuminated. In ”Auto“ the time base will be periodically started even
if there is no signal or when no triggers are generated because the
settings are incorrect. Signals of

20 Hz can not be triggered as

the automatic start will have occurred before the signal arrived.
Automatic triggering is possible with or without peak detection.
The LEVEL A/B

control will be active in both modes.

In peak detection mode the range of the level control is limited
to the peak-to-peak voltage of the signal. Without peak detection
any level can be set. If the trigger level is set such that no trig-
gers are generated the automatic triggering will nevertheless
start the time base. The signal will thus remain visible but will
be untriggered.
Whether peak detection is active or not depends on the mode
and the settings in ”FILTER“ (trigger coupling). The mode active
will be shown by the behaviour of the trigger point symbol when
turning the LEVEL knob.

16.2. Normal (trigger)

If the NORM-LED

lights up normal triggering was selected. In

normal trigger mode both the peak detection and the automatic
time base start will be disabled. Hence if there is no sufﬁ cient
trigger signal the screen will remain dark in analog mode. In
this mode there is no lower frequency limit for signals.

FILTER

(pushbutton)

After this pushbutton is depressed it will depend on the settings
chosen in MODE

(Edge, Video) which menu will be offered. In

XY mode the pushbuttons: MODE

, FILTER

and SOURCE

are disabled as XY displays can not be triggered.

17.1 Menu: Slope

The menu ”Edge“ will appear if ”Edge“ was selected in the ”Trig-
ger“ menu to be called with MODE

pushbutton and after the

FILTER

pushbutton was depressed. For further information

see ”Trigger coupling“ (Menu ”FILTER“) under the heading
”Triggering and time bases“ and the instrument speciﬁ cations.
The following settings are available:

17.1.1

Trig. Filter

–

AC:

The trigger signal is AC coupled via a large capacitor in

order to reach a low cut-off frequency.

Readout:

”Tr:Source, Slope, AC“

–

DC:

The trigger signal is DC coupled. No peak triggering is

possible.

Readout:

”Tr: Source, Slope, DC“

–

HF:

AC coupling with a small capacitor suppressing low

frequency signals. Hence the signal display and the trigger
signal derived are not any more identical. The trigger point
symbol is switched off. As a combination of HF coupling and
LF or Noise Reject is not meaningful both menu options will
not be shown.

Readout:

”Tr:Source, Slope, HF“.

–

LF:

The trigger signal is sent through a low pass in order to

suppress high frequency components. As this will already
suppress hf the noise rejection mode will be set to OFF
automatically.

Readout:

”Tr:Source, Slope, AC or DC, LF“.

–

Noise Reject:

Noise rejection (reduction) means a reduced

trigger ampliﬁ er bandwidth and consequently less trigger
signal noise.