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I want to discuss here what I believe is a common problem, yet I am often unable to solve it or advise a customer what to do about it - picking up 50/60Hz noise from the power lines. The below image is typical, and I often see this during installations. It's an HOPG sample in Tapping Mode scanned with 1Hz and 2Hz Scan Rate. That way you can actually count 25/12.5 peaks per line respectively.
What is the usual cause of this? Bad grounding? Should I always bring a grounding wire to ground the controllers? Would building a Faraday cage help? I've often seen this problem with Icons , shouldn't the Acoustic Hood act as a Faraday cage there? How do I hunt for the root problem, are there any E/M field detectors that might be usable here? Any suggestions and insights into this problem will be appreciated.
Jakub
Ok, if there is someone interested in how this problem was solved:
This particular problem happened during an installation of a new Icon and it went away after connecting the antivibration table to the compressed air source. We were waiting for a new compressor to come, but I didn't expect it would be the solution to the problem because of the 50Hz nature of the noise, which would suggest interference from power lines. After the antivibration table was inflated, the oscillation went away completely.
Hi Jakub,
I think the noise is probably comming from vibration rather than 50/60Hz electrical noise. Usually the 50/60Hz noise is quite small and tapping mode is insensitive to this kind of low frequency electrical noise. One way you can check is using high speed data capture to collect height sensor data for 15 seconds and plot the spectrum. My guess is the noise frequency might not be exactly 50/60Hz.
Yan
Some more information about the pictures above - I have now grounded both the controllers and the ebox with a grounding wire and the measurements still behave the same. I see hardly any detail, because the 50Hz noise is still visible. Can you advise?
I have kept an eye on your question. I compared my pictures with yours and found the noise of mine was not as strong as yours. The noise of my pictures is in the Angstrom range. I thought it was the nature noise of electricity. For sure the noise can be seen when the Height rang is around 1 or 2 nm.
I am curious that if the oscillation completely went away. Or if you make a cross section of your picture and small noise in angstrom range still can be seen?
BR,
Solong
Hi Solong,
I don't remember seeing an oscillation in the Angstrom range and I am not in front of the instrument now. The noise before had an amplitude of about 2nm and it was definitely related to the antivibration table not being inflated.
Awesome!
I have been in the similar trouble for several days. I almost check everything that I can check. And I am writing an e-mail to Bruker for help. After reading this message, I stop writing and go to check and fix the antivibration table. Now the noises are gone!
Thank you so much!