THORLABS PM320E, Руководство по эксплуатации

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© 2016 Thorlabs GmbH
3 Operating Instruction
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The new wavelength setting gets active when pressing the control button or the <OK> soft key.
3.2.2 Dark Current Adjustment
Photodiode sensors emit very small current levels, even when no photons hit the active area -
the so called dark current - that is temperature dependent and in the region of some nA for
Silicon and InGaAs sensors and up to some µA for Germanium sensors.
When measuring very small power levels this dark current can have an influence on the
measurement result and must be compensated by the dark current adjustment. This function
that can be reached by entering the <CHx Setup> and navigating to the ‘Dark Current’ menu,
can also be used to subtract ambient light.
To perform the adjustment, cover the sensor with the metal protection cap or when a fiber
connector is assembled, plug a fiber (laser switched off) and press the Control knob or press
the <Enter> soft button. The PM320E will automatically switch down to the smallest possible
measurement range, measure the photo current and take in account this value when
calculating the power reading. Press <Exit> to return to the measurement screen.
Display Dark Current Adjustment
3.2.3 Bandwidth Setting
The analog bandwidth setting mainly influences the analog outputs, for example in order to
subtract noise from the mains. The analog bandwidth can be set in the channel setup to
‘high’ (range dependent bandwidth) and ‘low’ (15 Hz bandwidth). The digital power readings
and the bar graph have a digital filtering (including a selectable 50/60Hz line filter); this
combined bandwidth approximately corresponds to the ‘low’ bandwidth setting.