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FocusMonitor FM+
10.3
Other errors
Error
Error during a measurement
Apart from the ambient
noise and zero offset,
no measuring signal is
available.
The measuring tip is
destroyed during the
measurement.
When measuring small
beams, an offset of the
recorded measuring
tracks to one another is
observed.
A lag of the signal in the
x-direction can become
visible in some cases
with the DFY-PS+ detector
and very small beams in
combination with a high
measuring tip velocity.
Slight differences in sensi-
tivity may occur when using
the DFY-PS+ detector
in the wavelength range
1,064 - 1,080 nm.
Tab. 10.1:
Other errors
Revision 08 EN - 08/2023
Possible cause
•
Data transmission error
•
Processor crash in the
measuring system
•
Program execution error
The device is not aligned
correctly.
The power density in the
focus is too low.
The selected resolution is too
low for smaller focus spots
(e.g. r
= 80 µm) and a maxi-
f
mum measuring window.
The measuring tip is defective.
The measuring tip is installed
incorrectly.
The signal enhancement is
too low.
The power density is too
high, igniting plasma on the
surface of the measuring tip.
Fluctuations in the synchro-
nism of the rotation disc
and delays in triggering the
trigger signal.
The response time of the
used photodiode of the DFY-
PS+ detector.
The upper limit of sensitivity
of the DFY-PS+ detector is
close to the wavelength of
solid-state lasers.
Remedy
1.
Restart the software.
2.
Turn off the supply voltage, turn it on again, and
start another reset cycle.
3.
Restart the computer
Check the device alignment to the laser beam.
Increase the laser power. The absolute power density in
the focus typically has to be several hundred kW/cm² to
achieve a significant measuring signal with a standard
measuring tip.
First measure outside the direct focus area. If this
does not lead to a result, increase the resolution
(e.g. 256 x 256).
Insert a new measuring tip, see chapter 11.3 „Check/
replace the measuring tip" on page 68.
Turn the measuring tip around.
Set the maximum enhancement and select the maximum
measuring range.
Increase the speed of the measuring tip, see appendix
B on page 79 and purge the measuring area with
inert gas.
Position the beam as close to the left edge of the window
as possible. The time interval between the trigger signal
and start of the measurement is then smaller and errors
can thus be reduced. Averaging is also often helpful in
this case.
For such measurements, PRIMES recommends the use
of the DFIG-PS+ detector.
For such measurements, PRIMES recommends the use
of the DFIG-PS+ detector, which provides a broader
wavelength range.
67
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