Fluke PM3370B user manual Trigger Coupling

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