Operating instructions

IMPROVING MEASUREMENT QUALITY

Improving measurement quality

Removing interfering signals

Interfering signals can be recognised because they have a fixed frequency,

usually a multiple of the local mains frequency (50 or 60 Hz) throughout

the image. Thus, they are manifested by straight lines that run throughout

the image.

Possible interference sources are:

• Mechanical vibrations from machines or heavy transformers in the envi-

ronment (e.g. pumps).

• Infrared light sources (light bulbs, sample illumination in an inverted

microscope).

• Electrical interference (in the electronics, or in electrical forces in the tip-

sample interaction).

Mechanical vibrations

To find out if the interference is due to mechanical vibrations:

- Measure the frequency of the vibrations.

These vibrations have a frequency that is (a multiple of) the rotation fre-

quency of the source. This frequency is usually not a multiple of the local

mains frequency, and may change slightly over time. Try the following to

find out if the interfering signal is due to mechanical vibrations:

- If possible, turn off all rotating machines (i.e. pumps) in the room.

- Change the vibration isolation by putting the Scan head directly on the

table, instead of on the Sample stage.

To reduce the influence of these vibrations, either improve the isolation of

these machines, or improve the isolation of the instrument by using a vibra-

tion isolation table (e.g. the optional TS-150 active vibration isolation table

option).