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how to reduce the noise in PCIe-6321 acquisition, to optimize wiring.

Hi all,

 

I want to optimize my wiring in term of noise reduction. I use a DAQ PCIe-6321 in my application. I want to acquire an analog signal from a sensor (+/- 4 Volts, resolution of 2 mV, output impedance of 100 ohms) using the DAQ. The frequency of the signal is below 2 kHz. My first question is about the most suitable cable to use (shielded, twisted, etc.)? What is also the best suitable input configuration to choose in Labview (differential, RSE or NRSE)?

Moreover, after processing of this data under Labview, I want to power an audio power amplifier (input impedance equal to 10 kohms) using the analog output of the DAQ. What is the most suitable cable to use to reduce the noise? Are there any other tips to optimize the wiring?

 

Thank you for your help and suggestions!

 

Cedric

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Hi Cedric51,

Here is a link to a Developer Zone that addresses your concerns.

Field Wiring and Noise Considerations for Analog Signals

Wear
National Instruments
Product Support Engineer
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Cedric,

 

The link provided by Wear is the best place to start.

 

No one can answer your questions because you do not provide enough information. The choice of cables and input configurations depends on the nature of your sensor.  Is its output floating or ground referenced? Where does it get its power? How is the power source grounded? What kinds of interfering sources are nearby?  If your source is a tachometer connected to a 100 kW motor with PWM speed control, the situation is quite different from an EMG preamplifier in a Faraday cage.

 

Lynn

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Hi guys,

 

I know that it is a bit late to reply but that is the perfect topic for what I am looking for!

 

I am currently working with acquisition systems using either PCI-6221 or PCIe-6321. Those systems are exactly the same but the results are different (see picture enclosed). We can see spikes and noise with the PCIe-6321 while we have the same conditions of measurements. 

 

Here is the NI setup:

- PCI-6221 + connector block CB-68LP + cable SHC68-68-EPM

- PCIe-6321 + connector block SCB-68A + cable SHC68-68-EPM

 

In one of the system equipped with PCIe-6321, I replaced all the devices like cables, detectors, motors and it doesn’t change anything. I also swapped the computer for one equipped with PCI-6221 and it works fine. It means that the problem really comes from the acquisition card.

 

So my question is: why is there such a difference between those models? Do I need to change the configuration in the card?

 

Thanks in advance.

 

Maxime  

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Hello MaxBI74,

 

No, the difference between the cards should not be that big. 

Is there a way we can test the PCIe alone? 

Maybe try a calibration procedure as directed by the following document?

http://www.ni.com/pdf/manuals/370937n.pdf

 

Also, is there a way we can measure the input you are reading with the cards? by switching cards,buit using  the same connector blocks.

 

 

"everything is achieveable through technology'
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