daq

[newestrookie]

Hi Everyone,

I'm totally a rookie with LabVIEW.  In fact, I took a Basic Course couple years ago (LabVIEW 7.0) but never have chance to used it.  I'm now back to learn LabVIEW... and... almost everything is new to me.  Anyway, here is my problem... I'm learning about how to use the multifunctional DAQ for taking measurements, etc.  I had a PCI-6111 DAQ installed to my PC; a CB-68LP terminal block; a SH68-68-EP shielded cable; a SHC68-68-EPM shielded cable and a SH68-68-D1 shielded cable.  Could anyone help me to answer the following questions?

1. Can I used the terminal block that I had with the PCI-6111 DAQ card?  If yes, what type of cables should I use?
2. How can I find pinout diagram of the DAQ?  I would like to find out, for example, what will be at pins 1, 2, 3, etc?

I'll really appreciate your helps.

Newestrookie

[NI-Bongo]

Hello newestrookie,

You can use your SH68-68-EP cable with the PCI-6111.  It is the recommended cable choice for that device.

The CB-68LP is a low-cost, unshielded terminal block generally used for counter/timer cards.  I don't think there is any reason you can't use it for the PCI-6111, but the BNC-2110 (BNC connectors) or SCB-68 (screw terminals) are the recommended terminal blocks for your device.

To find the pinout, open Measurement & Automation Explorer and find your device in the configuration window under My System»Devices and Interfaces»NI-DAQmx Devices»NI PCI-6111.  Right-click on the device name and select Device Pinouts.  This will bring up the pinout page from the user manual.  It can also be found in the user manual directly on page A-3.

S Series User Manual
http://www.ni.com/pdf/manuals/370781g.pdf

I hope this helps to get you started.

[newestrookie]

Hi John,

Thank you very much for your help.  This is absolutely a useful set of information for me.  I understand better about how the DAQ works now.  Thanks again.

Newestrookie

[newestrookie]

Hi John,

Sorry... it's me again...  I created a very simple VI using the DAQ assistance function.  From what I understood, the VI should run continuously until either the "STOP" button is pressed or an error happens.  There was an error during the run, however, after check the codes, I still could not understand why?  Could you please take a look at the codes from the attachment and help me to understand where was an error?  Thanks

Newestrookie

[NI-Bongo]

Hello again Newestrookie,

Which error code did you receive when running the VI?  One thing you may want to consider is to change the Acquisition Mode in the DAQ Assistant Timing Settings to 1 Sample (On Demand).  To simply monitor voltage levels, this should suffice. 

What me be happening is that you are acquiring data at 1kHz and reading from the buffer 100 samples at a time, but your loop has a 250 ms wait.  This means that the DAQ Assistant only gets 100 samples each time through the loop, but acquires approximately 250 samples.  This leaves about 150 samples in the buffer for each iteration of the loop and will overflow the buffer after several iterations.

Getting Started with NI-DAQmx
http://zone.ni.com/devzone/cda/tut/p/id/5434

[newestrookie]

Thanks again John.  I've changed the acquisiton mode to 'N-Samples' and kept everything else the same.  The VI seems to be run OK now.  If that's the case, could you please tell me when should I use the 'Continuous' mode and how?  Again, I really appreciate your helps.

Newestrookie 

[newestrookie]

Hi John,

I hate to keep bodering you... a new problem just happened... I tried to measure the output voltage from the same DC source using both AI0 and AI1 channels (just to make sure they both have the same reading) by went to the DAQ Assistance setup and changedthe input channel (from 0 to 1).  The results were not as I expected... AI0 channel always read the correct voltage (verified using the Fluke DMM), which is around 3V; AI1channel, on the other hand, always read a wrong voltage, which is approximately 0.9V.

I went back to double check the codes; nothing seemed to be wrong (to me).  Could you please help me to find out?  Thanks

NewestrookieAI0