Gentec-EO MACH 6 - Manual (Page 40)

Mach 6 User’s Manual Revision 2.1 40
Note that when the instrument is set back to internal trigger, the polarity is reset to rising
edge, and the trigger delay is reset to 0ns.
Trigger Level Tracking Setting
This applies to Internal Trigger Mode only. Since the Mach 6 uses a hardware trigger,
with a Pyroelectric probe the pulse that creates the trigger exhibits a DC drift, the trigger
level will appear to shift in relation to the pulse. At low duty cycle, the pulse baseline
will be stable and triggers will occur as intended. With high duty cycles the pulse will
drift negative. If this drift is greater than the set trigger level the instrument will stop
triggering and miss pulses. To prevent this, the trigger level must be corrected as the
pulse baseline drifts. Trigger Tracking monitors the DC level of the pulse and modifies
the trigger level so it remains at the set level in relation to the pulse. When triggering
stops or Mach 6 is disarmed, or trigger tracking is turned off, the trigger level returns to
its unmodified state.
It is possible for the Mach 6 to lose track of the trigger under certain conditions. See
figure 8.
Figure 8, Pulse Drift
Suppose trigger level tracking is off and a pulse with energy of 21μJ is being measured at
a very low repetition rate in the 200μJ range. The trigger level is set to 10%, or 20μJ, so
data is being acquired. Now suppose the repetition rate is turned to 100,000pps and the
signal drifts negative by 12%. The pulse energy is still 21μJ, but the “peak” of the pulse
is now at 18.5μJ. This is below the trigger level and data is now being missed. If trigger