NI-9203 generates noise pulses when acquired

[Sean365]

Hi Alex,

I dont have the option to "accept as solution", sorry.

Regards,

Seán

[Simon-lee]

Hi Alex,

Just a quick note to thank you for posting the NI-9203 signal noise. 

I was struggling but after following your suggestion of installing a 100uF cap noise went from 0.4ma to 0.04ma. 

Thanks again for all the hard work.

Simon

[Alex2012]

It has been awhile. I am ordering new measurement system. After having a chat with Swedish sale-man from NI I've expressed a wish to avoid ordering 9203. He started to dig why & how, and eventually next day another NI support guy called me. They opened ticket and then asked if I can perform more tests with new MAX and drivers from 2017. he believed that old drivers from 2015 had bugs which are fixed now in 2017. So I did some tests. Attached is the updated report (pp. 7-14). Unfortunately, NI-9203 still generating spikes even with drivers from 2017.

Results from the tests suggest that noisy spikes are produced by NI-9203 when following conditions
are satisfied:

• MAX or LabView task is running.
• More than one input is acquired by the task.

So, beside shunting capacitors, if you want guys to avoid noise, use one input only! A bit expensive solution for single 4-20mA channel for $500

[Henrik_Volkers]

Thank you for sharing the results of your investigations.

  just had a look at the specs..   funny couldn't find them at the ni page 🙂

Looks like real bad design...   

OK, I always try to awoid multiplexed inputs ...  should add that to my sig 😉

[K.C]

I have the same noise problem with Ni 9201 module in Crio 9073

[Alex2012]

Hi K.C.!

Well, it is always good to show your case in details, an oscillogram or other plot showing the noise.

Last year I have been contacted by NI and they analyzed my noise report. Then they did some tests in their lab and.... not surprisingly..., found no problem...

I am too lazy now to dig my emails and search their "perfectly smooth plots".

[Risuraj]

Still the same problem with NI 9203 with latest driver or this bug has removed??

if anyone using the same module please let me know.

[Alex2012]

I would say, it is not a bug, but rather a hardware feature 🙂

The only solution is to connect RC or inductive filter and then you will reduce your bandwidth.

[OfirHarari]

Hello,

We have the same problem with pressure reading & 9203 card. NI rep advised to use FFT and program a High Pass Filter to remove AC noise. Do you think it might help?

Thanks,

Ofir

[Alex2012]

Well, if you need to sample pressure measurements with a high rate and/or the labor cost is low for you, then sure, why not implement it and digitally filter it out? However, the spectrum of that noise (not really noise, but quasi-periodic garbage) may greatly depend on the impedance of your 4-20mA load/line, sampling rate, cable length etc etc. So, you would need to study those dependencies first and then adjust filtering algorithm accordingly. That will take time.

A simple solution is to put 22µF (or more) capacitor in parallel from that channel to the ground and forget about this problem. Unless you measure pressure of the shock wave from explosion or similar, you may rather need to average your readings anyway. So, capacitor will make a very good average implemented as simple passive hardware component.

Interesting that in your case NI were not denying this issue with 9203, in my case they tried to reproduced and of course did not found any problem, even sent me some plots with huge Y-scale and practically 0mA noise...