Need guidance in BNC terminals , NI 6363 BNC

[Hasham622x]

Hi,

Sorry for the late reply. If you don't mind, could you please guide me on whether the screw pins AI Sense 1 and AI Sense 2 are used in RSE, NRSE, or Differential (DIFF) configurations in the NI 6363 BNC and screw terminal setup?

Additionally, if I use all BNCs in differential mode as sixteen AI channels (all BNC AI terminals) by connecting the +ve BNC terminal to the signal and the -ve BNC terminal to AI GND, will the sampling rate of 2 MS/sec decrease to 130 KS/sec for sixteen channels, or to 65 KS/sec, considering that I am indirectly utilizing all 32 AI channels?

Kindly please guide

kind regards

Hasham

[ZYOng]

AI SENSE is for NRSE. See Table 1 in Field Wiring and Noise Considerations for Analog Signals

According to USB-6363 Specifications, the aggregated Multichannel maximum sampling rate is 1.00 MSample/s.

Hence you only get 62.5kS/s/ch for 16 channels.

[Hasham622x]

could you share your code 

[NIquist]

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@Hasham622x wrote:

could you share your code 

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🤔  You asked about DAQ wiring and sample rate specs.  What code are talking about?

[Hasham622x]

Hi,

Thank you for your reply. If you don’t mind, could you please guide me on whether I need to connect the AI GND point in differential mode, or if it is unnecessary? I am observing transient behavior in the captured data points, which makes me wonder if not utilizing AI GND in differential mode could be the cause of this issue.

Kind regards

Hasham

[santo_13]

You still need to connect AIGND when using differential mode as depicted in the image below depending on the kind of signal you're measuring.

[Hasham622x]

Hi,

Thanks for your reply. I am using a function (frequency) generator, where the +ve and -ve terminals serve as the +ve and -ve voltage inputs (AI+ and AI-) in differential mode, connected to the NI 6363 DAQ device.

Could you please guide me on where I should connect AI GND? In the circuit image you shared, AI GND is connected to both inputs via a 10kΩ resistor. Should I follow the same approach, or is it not necessary in my case?

Kindly please guide.

kind regards

Hasham

[NIquist]

We don't know.  The whole point in having all these DAQ wiring options is to accommodate the different types of hardware setups in the real world.  We're not in your lab, you are.  Try it both ways and see what works best. 

If your signal generator is plugged into a grounded AC outlet and so is your DAQ system (PCI or USB), you will probably NOT need the resistors.  If the generator is floating (no grounded outlet, battery powered), you may find the signal floating.  If it floats outside of the DAQ range, it will clip and you will read wrong values. 

[santo_13]

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@NIquist wrote:

We don't know.  The whole point in having all these DAQ wiring options is to accommodate the different types of hardware setups in the real world.  We're not in your lab, you are.  Try it both ways and see what works best. 

If your signal generator is plugged into a grounded AC outlet and so is your DAQ system (PCI or USB), you will probably NOT need the resistors.  If the generator is floating (no grounded outlet, battery powered), you may find the signal floating.  If it floats outside of the DAQ range, it will clip and you will read wrong values. 

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Agree with NIquist's comments.

Since the DAQ is USB and if you connect it to a laptop unplugged from mains, essentially, it is floating, then you need those bias resistors. Or if you can guarantee that both the function generator and the DAQ are someway connected to mains earth, you may not need the bias resistors.