Channels per Chassis on 9174 and 9178

[Munson1027]

I am trying to figure out the most cost effective means of driving as many digital output channels as possible using one of the cDAQ chassis.

The older cDAQ chassis (NI cDAQ 9172) listed a specification of 64 digital I/O channels per chassis.  I cannot find a similar specification for the NI cDAQ 9174 or the NI cDAQ 9178.  Are these both limited to 64 digital ouputs as well, or is the 9174 limited to half?  I can drive 64 digital output lines with two modules (NI 9476), so the numberslots in the chassis is nowhere near as important to me as the number of channels.

Thanks

Matt

[KyleBryson · Accepted solution]

Hi Matt,

I think I found the source that lists 64 DIO as a max on the cDAQ-9172: the data sheet linked off of the webpage.  This is incorrect.  All of the CompactDAQ chassis can support the maximum number of digital channels possible based on their number of slots; using 32 channel modules, this is 256 channels for the 9172 and 9178, and 128 channels for the 9174.  You can use 2 NI 9476 modules to control 64 lines in any CompactDAQ chassis.

Please keep in mind that you cannot use hardware-timed or counter/timer features through an NI 9476 module.  For details on support for those digital functions on each chassis, please consult the 'User Guide and Specifications' document for each chassis, which is more extensive than the datasheet.

I apologize for the documentation error that you found, and I have passed this along to be corrected.

Regards,
Kyle

[Munson1027]

Thanks Kyle,

Just got confirmation from my local rep on this as well, that the 64 channel limit is for correlated output, which makes sense because I don't think there are modules that go above 8 channels that can handle correlated output.  To follow up a little, if I put seven 9476's in and one 9472, could I use the hardware timed features for the 9472 while doing software timed/static output from the 9476's?

Thanks again

Matt

[KyleBryson]

Hi Matt,

You're welcome!  You can use the hardware timed features on the 9472 and software timed/static on seven 9476 modules.  On a cDAQ-9172, you'll need to put the 9472 in one of slots 1-4; on the cDAQ-9178, it can go in any slot.

Regards,
Kyle