Atrig Signal - Measurement Computing PCI-DAS6052 User Manual

PCI-DAS6052 User's Guide

ATRIG signal

In addition to standard digital trigger features, the PCI-DAS6052 also provides analog
triggering capability. When using the analog trigger, acquisitions may be started and
controlled via an analog signal. There are four trigger/gate modes available using the
analog trigger feature:
Trigger – positive or negative slope.
Gate – above reference or below reference.
Hysteresis – positive or negative hysteresis.
Window – inside or outside window.
The Trigger mode is used to start an acquisition sequence. The remaining modes provide
gating functions during an acquisition sequence which start and stop the acquisition
based on the gate condition.
There are two possible inputs for the analog trigger source. The first is the
AUXIN0/ATRIG pin on the 100-pin I/O connector. This is a software selectable
dual-purpose pin that supports either digital or analog trigger inputs. The source
selection defaults to analog trigger on power-up and may be modified at any time using
InstaCal. The input range on the ATRIG pin is always ±10V. 12-bit DACs are used to
set the HI and LO levels for the threshold(s). The threshold resolution in this mode is
4.88mV per step.
Caution! Remove all analog inputs before configuring this pin as a digital input. Any
voltage levels above ±15V in this configuration may cause damage to the product!
The post-gain version of any one of the 16 analog inputs may also be used as the analog
trigger source. In this mode, the voltage present on the first channel in the scan may be
used initiate the acquisition sequence.
Since the input to the analog trigger circuit has been scaled by the selected range, the
effective resolution of the thresholds is equal to the A/D's full-scale-range (±2.5V)
divided by 4096. For example, the ±2.5V range allows for 5V/4096, or 1.2 mV of
threshold resolution.
The following is a detailed description of each mode of operation. In each case a ±2V
triangle waveform is used as the ATRIG input source. The THRESH_HI is set to 1.0V
and the THRESH_LO signal is set to -1.0V.
In the following analog trigger signal diagrams, the bold portion of the waveform
indicates the data acquired for the given ATRIG mode.
4-12
Functional Details