Fluke PM-3390B, PM-3380B, PM-3370B, PM-3394B, PM-3384B user manual Pre- and post-triggering, Trace

USING THE COMBISCOPE INSTRUMENTS 3 - 27

3.4.1.4Pre- and post-triggering

When pre-triggering is selected, the real trace acquisition begins before the moment that the trigger occurs. Triggering occurs when the trigger conditions are satisfied and the instrument leaves the "Wait for TRIGger" state as shown in the trigger diagram of figure 3.3. In a similar way, post-triggering causes the acquisition to begin after the moment that the trigger occurs.

trigger moment

SENSe:SWEep:OFFSet:TIME

pre trigger

Trace

begin

total acquisition time

SENSe:SWEep:TIME

time axis

end

ST7190

trigger moment

Figure 3.8 Pre-triggering

SENSe:SWEep:OFFSet:TIME

post trigger

Trace

begin

total acquisition time

SENSe:SWEep:TIME

Figure 3.9 Post-triggering

time axis

end

ST7191

Pre- and post-triggering are programmed with the SENSe:SWEep:OFFSet:TIME command. A positive parameter value specifies a post-trigger delay, whereas, a negative value results in a pre-trigger view.

After *RST, the SENSe:SWEep:OFFSet:TIME is set to -0.005, which results in a pre-trigger view of 5 ms. Because the *RST value of the total acquisition time (SENSe:SWEep:TIME) is 10 ms, the trigger point is positioned in the middle of the trace.

PROGRAM EXAMPLE:

CALL	Send(0,	8,	"SENSe:SWEep:OFFSet:TIME	0.001",	1)	’1 ms post-trigger
CALL	Send(0,	8,	"SENSe:SWEep:OFFSet:TIME	-1E-3",	1)	’1 ms pre-trigger