Measuring a differential TTL

[GTAE2012]

Hi, all this is my first post.  I am trying to measure the frequency of a signal output by an RPM encoder attached to a motor shaft.  We have a circuit board inline which boosts signal and outputs the + DTTL and - DTTL signals.  How can I measure the differential in labview?  I have done basic analog signal data accquisition but I am new to digital signal accquisition and manipulation.

Before adding the circuit board we read RPMs using a counter from the BNC-2110 card and used a DAQmx creat channel (CI-Frequency) vi.  We ran into problems with signal noise which prompted the inclusion of the DTTL board.

I attempted to use the DAQ assistant to read in a digital signal but how do I take the differential of the two signals?

I am using Labview 8.6

I have this hardware available to use:

BNC-2110 (one of the two counters is in use)

SCXI-1001 chassis with SCXI-1600 USB interface

installed cards are:

SCXI 1520 with 1314 accessory

SCXI 1102B with 1303 accessory (may have all inputs in use)

SCXI 1125 with 1313 accessory

Any help is greatly appreciated.  Thanks

[Toader Mihai]

Hello,

One simple way to do this is by using analog differential input, and one of the examples in LabVIEW example finder.

To set up the differential input for the device simply add another property to the Property Node: Analog Input -> General Properties -> Input Configuration -> Terminal Configuration. Create a constant and select Differential.

If you need any clarification with this solution please let me know.

Regards,

Toader Mihai