I am experiencing a noise issue on my AFM. In addition to the common noises 1/f, white noise and I am having an additional noise on my signal trace. The signal is sinusoidal (wavy) at low frequency. I have replaced once the computer, the scanner, and the ADC>DAC box, the scanner. the problem seems to disappear when the ADC/DAC is replaced in some some system, but persist in different system with the same failing signature.
Can you identify which frequency in Hz? Try to use your computer without a power supply. Use instead only the battery.
Electrical problem with ground - seems You got Asylum system? Check cables, clean connectors.
It should be the 60Hz electrical noise.
One further issue cannot be completely neglected if your laboratory is located on the upper floors such as the mechanical oscillation of the building. It depends on the size and the materials of the building but it is responsible of a measurable noise level with frequency of few tens of Hz.
If the frequency is known (mostly I do not know because noise is caused via PWM) try to build simple noise filter, based on equation: f=1/(2*pi*R*C) where R is serially connected resistor, then the capacitor to ground. If you have trouble, first try to simulate filtering with Pspice. Of course - if You do not want experiments - forget about my tip
Or: Any correlations with little earth quakes ... or heavy winds?
or: traffic in building (walking persons next room, floor) or around the building (subway, train, busses, trucks)
or: talking people, phone rings...
Differences between perhaps busy working periods (Mo thru Fri) and Weekends; day/night?
Is it present independent of the approach status (i.e. for an engaged and withdrawn tip)?
If so, it is most likely an electrical interference problem. If it only occurs when the tip is engaged, it could be caused by building vibrations, electrical interference on scanner cables, sound (humming transformers).
None correlation with heartquake, I was measuring during the heartquake of 2013 in north of Italy and the measurement was no affected by noise because of the frequency was order of magnitudes lower than the AFM one.
Light bulb illumination can be a source; I have had it.
What kind of AFM do you have? Is a measuring cell opened?
if it is around 1 Hz it should rather be building vibrations, in that case I suppose you need an antivibration platform under your AFM
I assume it was not there before. It could be also not perfect alignment of the laser on the cantilever that shadows from the sample. Try to realign the laser on the tip. If you constantly see the low frequency noise then calculate the frequency and look for a source.
When you say low freq, how low? if 50-60Hz I suggest you check the line quality on your building earth first. Earth loops can require some expertise to reduce. Isolating transformers may help. Also, check that the chassis earth connections are good and turn your lighting off to check if there is a bad ballast in the fluoro. If it is lower freq then probably mechanical and suggestions above are good.
sorry on my previous message I didn't put enough attention on 'sinusoidal' noise fingerprint: the noise I mentioned, building or, say, acoustic vibrations, would hardly be periodical... (if not... a fan, for example)?
The only last source of periodic noise, not mentioned so far (if I'm not wrong), is the old 'optical lever laser' standing wave due to interference? This is periodic in space (distance) above the surface, but may perhaps couple in with time some mode when doing force-distance curves on the sample?
It can be feedback loop generation, in tapping modes if initial probe oscillation amplitude is too high and sample is flat, than there is no much signal for feedback and it become sensitive to noise, and so the positive feedback loop become the oscillator. You can either lower the oscillation amplitude in initial setup or decrease the feedback gain to get rid of it.
We are at the DMAIC process. Gathering data on different systems. The phenomenon occurs on all systems but one. By swapping the DAC/ADC box, in association with the scanner the problem seems to go away. So we have 3 variables. it seems that noise occurs after about 10-20mn. The Signal is sinusoidal to answer some of the question and the noise peak is in order of pm-nm. which is big in our world.
We are doing a false engage to answer to Daniil's question and no probe attached. the noise occurs mainly at -110 V of the Z sensor. the noise is on the Z not on the ZY.
Update: We troubleshooted down to the head-crystal assy and we are actively investigating the contamination as it seems that when we clean with DI water+ultrasonic, the noise seems to diminish
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