NI DAQ - not compatible with LabView ?

[Tripepperoni]

Hai, is it possible that my daq device ( NI usb-6251 screw terminal ) may be not fully compatible with Labview ? This card was produced probably before 2011 but I have installed NI DAQmx and it's visible in LabView. The question is if this device may send data which is not being read properly by LabView2014 ? ( values presented are fales )

I'm asking just in case, because device may be faulty.

Regards !

[Sam_Sharp]

Are you using NI DAQ (the old API/library) or DAQmx (the new one?) - the USB 6251 is supported by the latest version of DAQmx (15.5) so you should be fine but I think NI DAQ is no longer supported so probably won't work.

[Tripepperoni]

Well, if I remember well, I installed NI-DAQmx 14.5 version. Device is visible and I can configure channels and tasks.

So there is no possiblity for wrong communication between the device and LabView if it's visible and recognized ?

Regards !

[Sam_Sharp]

It's pretty unlikely - you could try the 'device self-test' function from MAX as an extra step but otherwise I'd suspect a hardware issue. What are the values you are getting versus what you are expecting? Are you sure you don't have a wiring issue?

[Tripepperoni]

I connected generator which generated rectangualar wave ~ 2,8V DC peak-to-peak. Then, I made a program with my daq device and connected it to a chart. It showed a constant value of 10,53 V. When I changed the max and min values for the input to 5 and - 5 ( from 10 and - 10 ) I got a constant value of 5,3 V. Chart showed straight, horizontal line. I checked the wires and they are ok.

[Sam_Sharp]

Before ruling out a hardware problem - it sounds like your input is floating to the maximum level (e.g. just above 10V for +- 10V input) - either your signal or ground is disconnected or your voltage input is too high for the module (not likely if you're using 2.8V).

How, exactly, do you have the module wired up and to what pins? Are you using RSE, NRSE or Differential measurements?

If you're using single-ended (RSE / NRSE), connect your AI pin to AI GND and AI SENSE. If you're using differential measurements, connect both AI pins (e.g. AI0 and AI8) to AI GND. If it is working correctly, you should see almost exactly 0V on the channel.

If you're still seeing max-range values - try another channel. If none of the channels work, then there's definitely a hardware issue (e.g. the ADC is broken). If one of the channels is broken, then it's an internal problem between the AI pin and the multiplexor.

Oh - it's also a good idea to use the NI MAX test panels for this - helps avoid any problems with scaling etc.

[Tripepperoni]

Generally I use SE mode. My external circuit gives one wire at the output per thermocouple, so I plug the output wire to AI# (#-number of the channel) and I plug AI GND to the external circuit GND. I assume that the grounding is shared so I don't have to wire all AI GND together and then wire them to my external ground.

The only thing is that, external circuit GND is done as a minus. ( not zero but minus is like a GND there )

Here's the pinout for my device http://digital.natinst.com/public.nsf/$CXIV/ATTACH-AEEE-7QVNHJ/$FILE/Screenshot04.jpg 

I don't know where the AI SENSE is ( i know it's for NRSE which I don't use) 😞

I have to check other channels, because I managed to check only 2 from 16 available.

I'll try to make a self test tomorrow and see if everything is right.

Regards