The SCB-68 is actually just a connector block. The data acquisition card would have a model number like PCI-6220 or PCI-6040E. You can give us the actual model number of the card by looking in the Measurement and Automation Explorer under 'My System>Devices and Interfaces>NI-DAQmx Devices'.
It sounds like you have a Multifunction DAQ card. These only have two counters.
As far as I know, there are no examples of using analog inputs to do precise counting. It certainly could be done, but it would be a lot of coding and the accuracy of the results would not be as precise as using counters. You might want to look at some of the "Point by Point" VIs. There's a Zero crossing and a Boolean Crossing VI that may give pretty good results.
The best solution would be to use a Counter card. The PCI-6602 has 8 counters. This would give you enough to make all the measurements you need. If you have more of the multifunction cards available, you can use the counters from multiple cards to do this.
Can you please help me how to wire the Incremental shaft encoder to the NI SCB 68 which allows digital inputs and outputs to and from the PXI 7813R DIO Card.I am very much stuck up with this problem. Pl reply ASAP.