Performing Retriggerable Analog Input Using Two Counters

DESCRIPTION:
This VI uses an external trigger to repeatedly acquire multiple scans.

NOTE: This VI will only work on E Series or 611X devices.

This VI uses a programmable scan clock to retrieve data from one or more analog input channels. The programmable scan clock is implemented using two general purpose counters. An external signal, the trigger, is connected to the gate pin of Counter 1. When it receives a trigger, Counter 1 gates Counter 0, which generates a finite pulse train, the scan clock.

This is a buffered acquisition, meaning that the data are stored in an intermediate memory buffer after they are acquired from the DAQ device. Data are retrieved from that buffer and displayed on the graph. For simplicity, this VI uses AI Clock Config.vi to configure the scan clock..

INSTRUCTIONS:
1. Enter the device number, channels, buffer size, read size, buffer mode, scans per trigger, and scanning frequency.
2. Make the appropriate I/O connections as explained below.
3. Run the VI.
4. The scan backlog lets you know if your VI is reading data from the software buffer fast enough to keep up with the rate at which your device is writing data to that buffer.

KEY PARAMETERS:
This VI shows how to use the intermediate analog input DAQ VIs and counter examples to set up a retriggerable finite scan clock.

I/O CONNECTIONS:
Connect to the input channels on the I/O connector for your device to match the channels you have chosen on the front panel of this VI. For example ACH0 for analog input channel 0.

E Series devices:
Connect your scan clock to PFI7/STARTSCAN.
Connect your scan trigger to PFI4/GPCTR1 gate.

To find the actual pin numbers, refer to your hardware user manual.

DAQ VIs USED:
AI Config.vi, AI Start.vi, AI Read.vi, AI Clear.vi.
Finite Pulse Train (STC).vi, Counter Control.vi

Requirements

Filename: retrig_acq&graph_n_scans.llb

Software Requirements

Application Software: LabVIEW Full Development System 5.0.1
Language(s): LabVIEW

Hardware Requirements

Hardware Group: Multifunction DAQ (MIO)
Driver: Traditional NI-DAQ (Legacy) 6.5.0

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