Problems with cDAQ-9174 and NI 9201 Module

[David-Baratheon]

Hi everyone.

I am testing some hardware that I have just received and I have a few problems and questions, if anyone can help it would be great.

Firstly, I couldn't work out from the datasheet what the NC and COM ports were:

http://www.ni.com/datasheet/pdf/en/ds-184

I am trying to connect it to a signal generator and just view the signal in NI MAX on the test panel, but the signal doesn't look right at the moment. The following image shows what I am seeing from what is supposed to be a 10V 100Hz Sine Wave from the sig gen

[GerdW]

Hi David,

why don't you read the manual of your cRIO manual?

[David-Baratheon]

I've had a look through and I could see a reference to the COM signal being a common ground, but couldn't see anything regarding the NC terminal

[GerdW · Accepted solution]

Hi David,

NC being "not connected" - what more information do you need?

[David-Baratheon]

Ok so basically don't connect it to anything or use it for anything? What is the point of it then?

I did a search for NI NC Not Connected and seems I am not the only one confused by this:

http://forums.ni.com/t5/Signal-Conditioning/What-is-the-NC-terminal-on-the-NI-9211/td-p/2532504

I think NI could probabily make this a little clearer on their documentation.

Anyway, mystery solved, many thanks.

As a follow up, what do you think could be the reason I am not seeing a sine wave?

[GerdW]

Hi David,

What is the point of it then?

When you look at the images in your manual you will notice you need 9 contacts (8 AI + 1 COM), but the connector provides 10 contacts. This one spare contact is marked NC and isn't used in the module. Even when you connect a wire to this contact it will have no influence…

[David-Baratheon]

Ok so NI connectors justr come with 10 terminals as standard, and any unused terminals will just be NC.

What do you recommend regarding the signal generator?

[GerdW]

Hi David,

yes, NI uses a small collection of standard connectors and any unused pin will be NC.

What kind of recommendation on your siggen do you expect?

We don't know what you tried so far.

We don't know how you wired DAQ and siggen.

We don't know how you configured your siggen.

We don't know anything about your setup…

[David-Baratheon]

BNC connector with probe connected to AI0 and ground connected to COM terminal. I have already mentioned what frequency and amplitude I am using and a screenshot of NI MAX  to show my setup. I am not sure what more information I can give.

[GerdW]

Hi David,

use a "continuous" sampling mode with your AI instead of "on demand".

Use a sample rate of atleast twice your main signal frequency (as Nyquist says), better use 10times the signal frequency…