FUNCTION REFERENCE

5 - 79

TRIGGER COUPLING

Description:

Trigger coupling is used to optimize the trigger stability for different signal types.

The filter modes ac and dc are identical to those of the vertical inputs. Refer to function INPUT COUPLING.

Lf-reject cuts off lower frequencies; triggering occurs on signals between 30 kHz and full bandwidth.

Hf-reject cuts off higher frequencies; triggering occurs on signal frequencies lower then 30 kHz. The following figure explains ac, lf-reject, and hf-reject.

Noise ’on’ improves trigger stability for noisy signals. By enlarging the trigger gap (of MAIN TB and DEL’D TB) the triggering becomes less sensitive to noise.

The MAIN TB trigger coupling can be selected in the menu under the TRIGGER menu key. For DEL’D TB, the menu under the DTB menu key is used; the selection is possible in ’triggered’ mode (ch1, ch2 and ext trig) only.

 

ac-coupled

0dB

0dB

3dB

3dB

10Hz

FULL

 

BANDWITH

FREQ.

 

lf-reject

 

hf-reject

 

 

0dB

 

 

 

3dB

 

30kHz

FULL

30kHz

FULL

 

BANDWITH

 

BANDWITH

 

FREQ.

 

FREQ.

MAT4218

Effect of trigger coupling modes

Presence of trigger level indicators (T-, D-) as a function of trigger coupling and other oscilloscope settings:

Trigger

Vertical

Trigger level indicator

coupling

input coupling

 

 

 

 

ac

dc

off

dc

dc

on

lf-rej

dc

off

hf-rej

dc

on

 

 

 

all settings

ac

on

 

 

 

if level-pp is on

 

off

 

 

 

Page 199
Image 199
Fluke PM3370B user manual Trigger Coupling