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GX3748 Series

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48 Channel Threshold Comparator FPGA PXI Card

  • 48 Threshold Comparator Channels
  • Timestamp Capability on Selected Channels
  • Wide Input Voltage Range: 0 to 50 volts
  • PXI hybrid slot compatible


The GX3748 is a user configurable, FPGA-based, 3U PXI card which features 48 voltage comparator channels.  The daughter board interfaces to the GX3700 FPGA baseboard which employs the Altera Stratix  III FPGA.  Each input channel can accept input voltage signals from 0 to 50 volts, with programmable threshold levels. Three of the 48 channels are supported by the board's timestamp event feature.


The GX3748 offers the following capabilities:
  • 48 threshold comparators
  • Timestamp capabilities on any three of the 48 channels
  • Programmable window threshold comparator for 16 channels
  • Programmable level threshold level for 32 channels
  • 0 to 50 volt input voltage range
  • 3 Digitizer channels
  • Voltage measurement on all channels
  • Selectable pull-up / pull-down resistors on each input channel
  • Cable ID input
The GX3748 has three modes of operation: direct read of each threshold comparator state, generation of a system interrupt or a PXI trigger based on the occurrence of a pre-defined comparator state event, and timestamp functionality for 3 of the 48 comparator channels. Any single channel from each group can be connected to a digitizer with 87,300 sample memory; additionally, the voltage level for all 48 channels can be read. Four programmable voltage sources provide the 2 threshold levels for the window comparators with the remaining two voltage sources providing the threshold levels for channels 17 to 32 and channels 33 to 48 respectively.

Timestamp functionality records both the state and time of events for three of the 48 channels. Any of the 48 channels can be selected for time stamping. Minimum recording time is 4 minutes with 1 uSec of resolution. Recording time will be longer with lower timestamp resolution. The user has the ability to capture all states or only transitions.

The module has access to all of the PXI bus resources including the PXI 10 MHz clock, the local bus, and the PXI triggers; allowing the user to create a custom instrument which incorporates all PXI bus resources. Control and access to the FPGA is provided via the GX3748's driver which includes the ability to download compiled FPGA code as well as perform register reads and writes.

Programming and Software

The board is supplied with the GxFPGA library, a software package that includes a virtual instrument panel, and a Windows 32/64-bit DLL driver library and documentation. The virtual panel can be used to interactively program and control the instrument from a window that displays the instrument’s current settings and status. In addition, interface files are provided to support access to programming tools and languages such as ATEasy, LabVIEW, LabVIEW/Real-Time, C/C++, Microsoft Visual Basic®, Delphi, and Pascal. An On-Line help file and PDF User's Guide provides documentation that includes instructions for installing, using and programming the board.


  • Automatic Test Equipment (ATE)
  • Custom interface emulation
  • Custom instrumentation