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The signal noise is too large, what can I do?

By
Pablo Doerig
on 8/31/18, 8:30 AM 94 views

When I perform a measurement the noise in the force signal seems very high. Can I reduce that somehow?

This question has been included in the official documentation.

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Pablo Doerig

--Pablo Doerig--

1046
| 3 0 2
Glattbrugg, Switzerland
--Pablo Doerig--
Pablo Doerig
On 8/31/18, 8:39 AM

If you are not satisfied with the noise during your AFM experiments, here are a few points you likely can improve.

Ground noise

PASSIVE VIBRATION ISOLATION

There are a few tricks how you can improve the passive isolation of your setup against mechanical ground vibrations:

  • Use a robust, massive table.
  • Use a table with integrated passive damping. Either an optical table with pneumatics or a dedicated microscopy table.
  • Place the table close to a load-bearing wall, if possible in the corner. This will reduce mechanical noise pickup from people walking around.
  • Add weights to the table, the heavier the better.
  • Economic bench-top solution: Place a thick stone plate on cork pads and use it as base for your microscope.

ACTIVE VIBRATION ISOLATION

Active damping can significantly reduce mechanical noise transported via the ground to your setup. It will not cancel acoustic noise which is transported via air.

An economic approach is to add a bench-top solution.

Acoustic Noise

Minimize ventilation

If you work with living cells it is likely that you have an incubator box with ventilation around your setup. Reducing the ventilation intensity can have a big effect on the noise during your measurements.

Remove all devices with active air cooling (fan) from the microscope table. The cooling fan of electronic devices can introduce significant mechanical vibrations to the setup. Even if it only touches the table with a cable. This includes:

  • The computer
  • Any measurement- or control electronics with fan
  • The microscope camera (if cooled by fan)

For the microscope camera it is sometimes possible to disable the cooling temporarily. Switching to water-cooling can also reduce vibrations, but will not eliminate it completely.

Ventilation in the lab can generate audible acoustic noise which disturbs your measurement. Turning it off in vicinity to the AFM or installing an acoustic shield can help a lot.

Shield with a box

You can improve acoustic isolation by having an isolation box around your setup. Ask your AFM supplier for the recommended solutions.

Electrical Noise

Electrical noise can also impact your measurements.

The most important advice here is to ground all your electrical components well and to the same power outlet. If you still see electrical noise it is often due to worn out cables. Contact your AFM supplier for support in this case.

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Asked: 8/31/18, 8:30 AM
Seen: 94 times
Last updated: 10/12/18, 9:57 AM