Noise in the Analog Input Signal - MCC DAQ USB-205

[Akshat Agha]

Hello,

I am using a MCC DAQ USB-205 to capture an analog voltage (-10 to 10V). The general noise level observed in the signal is 0.01 V, but I am noticing a sudden spike (0.05 Volt) in the signal every 4-5 seconds (Screenshot attached).

I have tried the following:

1. Tried changing the AI channel connection from AI0 to AI2. Result: Same behavior was noticed. 

2. Tried replacing the MCC DAQ with a new DAQ of the same model. Result: Same behavior was noticed. Please see the attached screenshots for the two DAQ signals.

 

3. The signal was split from the source into two parts and captured simultaneously with a NI DAQ USB-6001. The NI DAQ is showing a much smoother signal with no spiked. 

 

What could be the cause of this problem and how to resolve it? Please advise.

 

Thanks

Akshat 

[Fausto]

Hello @Akshat Agha.

The USB-205 has a 12-bit A/D and supports single-ended connections.

https://www.mccdaq.com/pdfs/manuals/USB-205.pdf

The NI USB-6001 has a 14-bit A/D and supports both differential and single-ended connections.

https://www.ni.com/docs/en-US/bundle/usb-6001-specs/resource/374369a.pdf

The two devices are not the same.

What is the source of your signal?

Are you using a laptop or PC? 

Is your signal source grounded or floating?

Are there any motors, pumps or EMF emitting equipment nearby?

Retest the signal source to the USB-205 module, but do not split the signal to another device.  Verify the screw terminal connections are secured on the USB-205.   

Regards,

Fausto

 

[Akshat Agha]

Hello @Fausto

Thanks for your response. 

While debugging, I am using both the DAQs with single-ended connections (not differential). In general, I understand that a 14 bit A/D has a better resolution than a 12 bit A/D. Would that also affect the base noise and the spike that I am noticing?

The signal is coming from an output box attached to a universal load frame. It is actually a force signal (50kN full scale of 10V) from a load cell.

I am using a PC.

The signal is grounded. 

There are pumps and motors in the lab but not in close proximity to the DAQ or the BNC cable.

I have tried attaching the DAQ to another machine, at a different location in the lab, with a different signal source, and I am noticing the same behavior. 

Please advise.

Thanks

Akshat 

      

[Fausto]

Hello @Akshat Agha.

Differential input connections would help with the noise.

Connect a short wire from the analog input channel to the ground screw terminal on the USB-205.  Acquire data to show you the noise level.  Run a test with that system and no other equipment running in the lab.  Next, using the same wire configuration, run a test with motors and pumps running.  Lastly, run the test with a different system in another location.  Compare the results from those tests, so you know the level of noise to expect in the data.

Regards,

Fausto