THORLABS M2MS, Руководство по эксплуатации

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BP209 Series 6 The Graphics User Interface (GUI)
Rev: 8.1, 14-Feb-2022 © 2022 Thorlabs Page 31
6.5.3.1 Gain, Bandwidth and Baseline
Gain and Bandwidth are the parameters of the photo current amplifier. Higher bandwidth is re-
commended to achieve high resolution when measuring small beam diameters. The bandwidth
can be set between 16 kHz and 660 kHz, if the full 9.0 mm aperture width is used, and between
16 kHz and 1000 kHz, if the 0.9 mm aperture is used for measurement.
Each time the software is started, gain is set to Auto, bandwidth to 125 kHz and the Baseline
Correction is set to Auto. This is the preferred setting for most measurements. However, in
some cases, e.g. measurement of
pulsed lasers , it is recommended that these settings be
changed manually.
Baseline Correction
The baseline is the ADC output signal that originates from the photo detector's dark current, the
output offset and noise of the ADC. It results in a beam profile shift away from the zero line. En-
abling the Auto Baseline Correction, this influence is compensated. It is recommended to have
it enabled.
6.5.3.2 Scan Rate
Scan Rate
Here, the actual scan rate (drum rotation speed) is displayed
Target Scan Rate
This is the rotation speed of the drum in s
-1
. The entered value is transformed into a control
voltage for the drum drive. Values between 2 and 20 s
-1
can be entered either numerically or by
clicking to the arrows attached to the numeric box or by shifting the slider.
Scan Rate Correction
The actual rotation speed may differ from the entered target scan rate due to the drum drive
warming up: The longer the unit operates, the faster the drive runs at the same control voltage.
Enabling Scan Rate Correction, a control loop will maintain the scan rate close to the target val-
ue.
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