Teledyne SP Devices ADQ14, User Manual

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Classification Revision
Public PA1
Document ID Print date
18-2074 2018-04-06
pulse, this means that the signal has to visit ADC codes equal to or less than the trigger arm level.
Following a trigger event, the system is automatically disarmed until the arming criteria is met once
again.
• Fig. 2c —the reset arm level
The arming mechanism for the reset event is identical to that of the trigger event apart from one
detail: they are mirror versions of each other. In order for the falling edge of the pulse to generate a
reset event, the signal has to visit ADC codes equal to or greater than the reset arm level. Following
a reset event, the system is automatically disarmed until the arming criteria is met once again.
• Figs. 2d and 2e —false events
The arming mechanisms are what enables the protection of the data stream against false events.
However, this protection hinges on the hysteresis values input by the user to work correctly. As
shown in Fig. 2d , badly configured arm levels may have the same effect as not having them at all.
The arming levels should be set at least in the same range as the noise to be effective, as
shown in Fig. 2e .
For completeness, the conditions to generate a trigger or reset event are stated in ( 3 ) and ( 4 ) for positive
and negative pulses, respectively. The data at time instance n is denoted x [ n ] .
Positive pulses
Trigger event: x [ n ] ≥ Trigger level
Reset event: x [ n ] ≤ Reset level
(3)
Negative pulses
Trigger event: x [ n ]
≤
Trigger level
Reset event: x [ n ]
≥
Reset level
(4)
4.3.1 Edge Windows
The values discussed in the previous section target the vertical characteristics of a pulse. How the
horizontal characteristics of a pulse are treated by the pulse detection firmware are discussed in more
detail in Sections 4.11 and 4.12 . However, this section will introduce the leading edge window (LEW)
and the trailing edge window (TEW). The names hint at their purpose; the former defines a window in
time before the trigger event while the latter defines a window after the reset event, as shown in Fig. 3 .
These windows extend the region of interest outward from the pulse.

Note
The leading edge window and trailing edge window are two fixed-length regions that surround the
pulse and allow the user to extend the region of interest.
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