Hi Pta,
NI does have a newer USB version of the
PCI card, and in fact NI sells a couple of different versions in different form
factors, but they all have the same functionality. As you observed, the only differences are in
how you would connect your signals.
Allow me to explain the differences.
PCI/PCIe/PXI/PXIe 6251
Each of these versions require a 68-pin
cable and a terminal block (break out box).
To share counter signals between two of these cards, the appropriate screw
terminals on each terminal block are connected with wires. This is what you currently have setup.
USB-6251
This version has the DAQ device and the
terminal block combined into one unit. No
separate terminal block or 68-pin cable is needed. To share counter signals
between the cards, the appropriate screw terminals on each device are connected
with wires.
USB-6251 Mass Termination
This version is much like the PCI version.
It has a 68-pin connection and requires a 68-pin cable and a separate terminal
block. To share counter signals between
two of these cards, the appropriate screw terminals on each terminal block are
connected with wires.
USB-6251 BNC
This version has the DAQ device and a
modified terminal block combined into one unit.
It has several BNC connectors for analog and digital inputs and outputs
as well as smaller terminal block for the remaining signals. No additional
68-pin cable or terminal block is needed.
There are several ways to share counter signals between two of these
cards. They can be wired directly with
through the appropriate screw terminals on the device or shared through a user
defined BNC connection.
Either way you go, the functionality for
all is the same. You can even mix and match card types and still be able to
share the counter signals quite easily.
A good resource for looking at the
pinouts for each device can be found in the Appendix of the M-Series Manual and the NI 625x
Specifications.
Hope this helps.
Jared T.
