I am using a MEMS Accelerometer (ADXL1001), along with the EVAL board and an NI 9234 DAQ module to acquire the signal. I am using a RG58 coaxial cable to connect the sensor output (2 connector pins, Vout and Ground on the EVAL board) to the DAQ input (BNC connector).

However, I noticed that there's an interference and I see a small peak at 50 Hz frequency in the FFT of the signal (since the signal cable was lying near to a power amplifier). And on shutting the power amplifier OFF, the peak disappeared (no surprise).

My question is, which type of cable should be used (coaxial, shielded twisted pair or any other?) to achieve the best noise performance and to make sure that there's (almost) no interference.

Some addtional information:

*The sensor measures frequencies up to 20 kHz and the voltage varies from 0 to 5 volts, so the cable should be accordingly. *The DAQ (NI 9234) has a pseudo-differential configuration). (Does that impact the type of cable that can be used?)

Thanks in advance :)


I've used single shielded RG178 with the NI 9234 in the past with good results.

The ADXL1001 has a single-ended output, and pseudo-differential acquisition usually has poor common mode rejection ratio. Twisting pairs is a tactic to turn EMI into common mode noise, but since you don't have a differential signal nor acquisition hardware with good common mode rejection, the best cable for you is a shielded coax.

Your goal of "(almost) no interference" may be difficult; there is only so much you can do with the physics of shielding to reduce noise in the signal.

You can try the various AC/DC coupling options on the 9234 and see if one of them is better. AC coupling dampens low frequencies. If 50Hz is not in your frequency range of interest, consider adding an analog or digital filter. Failing that, hopefully the "small peak" you describe is small enough compared to the signal you are interested in for it to be ignored.

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