Cronologic Ndigo5G-10, User Manual

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Trigger
Gate
Gate Start
Gate Stop
Figure 2.21: Gate and delay functionality: When a trigger occurs, the gate opens after a set
period of time (“gate start”) and closes when it reaches “gate stop”.
Gating Example 1: Suppression of Noise After Starting an Acquisition
In mass spectrometer and other experiments, noise while starting data acquisition can result
in undesired trigger events for that time period. To prevent noise in the output data, a gating
block could be used to suppress all triggers during start-up.
The following example illustrates the use of a gating block to prevent noise: The GATEinput
transmits a pulse on each acquisition start. The trigger structure of the GATE input is used to
select pulse polarity. Then, the GATE trigger is selected as gating block input and the gating
block’s start parameter is set to 0. The stop parameter is set to the desired length measured in
3.2ns clock cycle and negate is set to true. The gating block will now output a low pulse of the
desired length whenever there is a pulse on the GATE input.
Enabling this gating block as an AND input to the trigger block, for which noise shall be
suppressed.
Gating Example 2: Delayed Trigger
To sample a short window at a specified time after a trigger event on a channel, the gating
block can be used to create a delayed trigger. To do this, one of the triggers of the channel of
interested is configured to the desired parameters by selecting the threshold, setting the edge
polarity and enabling edge triggering.
Instead of directly using this trigger as input to the trigger block’s input matrix, the trigger is
selected as an input to a gating block. The block is configured to start = delay [in 3.2ns clock
cycles] and stop = start + 1, negate = f alse . This causes the gating block to produce a one
clock cycle pulse on its output after the specified delay.
To send this pulse to the trigger block, the gating block must be enabled in the trigger block’s
AND matrix and the ONE trigger source must be selected.
Gating Example 3: Dual Level Trigger
The gates provide AND connections between each other (see fig. 2.19 ) which can be used for
example in a dual level trigger. For the acquisition of signal data with amplitudes between a
lower and an upper bound, for example, two level triggers can be connected (see fig.
2.22 ): a
falling level trigger with an upper threshold and a rising level trigger with a lower threshold.
cronologic GmbH & Co. KG 16 Ndigo5G User Guide