I tried several ways to capture analog and digital signals. I would need more than the standard two allowed on the NI-9174, so I came up with this using digital lines on the NI-9401 cDAQ. What do you think about this method?
The NI-9174 is a cDAQ chassis and does not directly measure analog or digital signals so you will need to use the C-series moduels (such as the NI-9401 as you stated). Maybe you could clarify what your are trying to acomplish.
<Brian Aswege | Applications Engineering | National Instruments>
Their are only 2 counters provided on the NI-9174 and have using the 9401 you would have to use slot 5 or 6. I was asking if the attached would be a good way to read digital signals (frequency) using the NI-9174 and the 9401 and have 8 channels instead of being limited to 2. You also wouldn't have to worry about which slot the 9401 was in.
After looking over your post and your code, it looks like you want to take a frequency measurement with a NI 9401 in a cDAQ-9174. Currently you are using a Digital Input task to perform this measurement. I was suggest though to use counters to implement this measurement. I have added an example to this post that will help you get started with this. I am assuming that you are working with low Frequency digital signals.
As for the hardware configuration, the 9401 doesn't have to be placed in any particular slot for the NI-9174 but if you have a NI-9172, then you would have to place this module in slot 5 or 6. Finally, you are look at the device pinout in MAX to find out where to connect your sensor to it.
I hope this information helps but if you have any more questions, feel free to post.