ADLINK DAQ/PXI-2000 series synchronous acquisition card configuration and triggering

Assistive Function Input (AFI) provides strong flexibility:

EXTTIMEBASE: Replace the internal 40MHz clock for custom sampling rates (1-40MHz).

AFI [0] can be configured as an external ADCONV (directly controlling A/D conversion) or an external SCAN_START, suitable for external event triggered sampling.

AFI [1] can be configured as an external DAWR (directly controlling D/A updates).

EXTDTRIG/EXTWFTRIG: External digital trigger inputs for AI and AO, respectively.

The System Synchronization Interface (SSI) supports multi card cascading (PCI version via 20 pin ribbon cable, PXI version via backplane trigger cable). Users can specify the internal timing signals of any card (TIMEBASE, ADCONV, SCAN_START, AD_TRIG, DA_TRIG, DAWR) as the master output, and other cards as slave receivers to achieve multi card synchronous sampling or waveform output, which is particularly suitable for multi-channel expansion (such as 4-card synchronous implementation of 16 channels).

Detailed explanation of trigger source and simulated trigger

In addition to software triggering and external digital triggering (edge detection), analog triggering is a major feature of this card. The analog trigger circuit can select the EXTATRIG pin (external analog input, range ± 10V, resolution about 78mV) or the selected ADC input channel (within full range, 8-bit resolution) as the source. 5 triggering conditions:

Below Low: Triggered when the signal falls below a low threshold.

Above High: Triggered when the signal exceeds a high threshold.

Inside Region: Triggered when the signal is between high and low thresholds.

High Hysteresis: Triggered when rising above a high threshold, while a low threshold determines hysteresis.

Low Hysteresis: Triggered when the drop crosses a low threshold, while a high threshold determines hysteresis.

These conditions are implemented through two thresholds and software configuration, which can effectively prevent false triggering caused by noise. The simulated triggering bandwidth is about 400kHz, suitable for automatic triggering scenarios that depend on signal levels.

Calibration and maintenance

The board is equipped with a precision reference source (5.000V, temperature drift ± 2ppm/° C, long-term stability 6ppm/1000Hr). At the factory, the calibration constant is written into the default area of the EEPROM, and three user modifiable areas are provided. It is recommended to perform automatic calibration (without external equipment) after preheating the installation environment for 15 minutes, and the software will automatically measure and correct offset and gain errors. After calibration, the new constant can be stored in any user area and labeled with a date/temperature for quick recovery under different environmental conditions.

Typical accuracy before and after calibration:

Offset error: ≤± 60mV before calibration, ≤± 1mV after calibration;

Gain error: ≤± 0.1% after calibration in 2010, and ≤± 0.03% in 2005/2006/2016.

Attention: All external connection cables must be removed before automatic calibration, as the D/A output may change during the calibration process.

Software Support and Rapid Development

ADLINK provides a multi-level software stack:

D2K-DASK: A DLL library for Windows 98/NT/2000/XP, supporting VB/VC+/Delphi/BC5, etc., with binary compatibility.

D2K-DASK/X: Linux shared library, supporting GNU C/C++.

DAQ-LabVIEW PnP: LabVIEW VI library, provided for free.

D2K-OCX: ActiveX control, easy to quickly build interfaces.

DAQBench (Business Edition): A complete collection of ActiveX controls, including data display and analysis.

All drivers and sample code are included in the accompanying CD, and a two-hour trial mode is provided (some software requires a license). Developers can easily configure channels, gains, trigger modes, and DMA buffers through APIs without worrying about underlying register operations.