© 2020 Thorlabs
9 Appendix
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Therefore, the PM100USB has a resolution of 1 µV at the lowest measurement range (1
mV). The power resolution depends on the used sensor.
Voltage input
(pyroelectric sensors): The resolution is specified as:
100 µV / responsivity value [V/J]
Therefore, the PM100USB has a resolution of 100 µV at the lowest measurement range (200
mV . The energy resolution depends on the used sensor.
·
Measurement Uncertainty
of the PM100USB is the current (voltage) measurement accur-
acy. It is given in % f.s. (% of the full scale value). Please note that the accuracy of the power
meter is different from the measurement uncertainty of the sensor.
·
Wavelength Correction
is the value that can be entered to the power meter in order to ap-
ply the correct responsivity and to receive a corrected measurement result.
In case of a calibrated Thorlabs sensor, the actual wavelength is entered directly. The power
meter retrieves the respective responsivity from the calibration table that was saved to the
DE-9 connector memory and uses this value for power or energy calculation.
In case of a custom sensor, the correct responsivity needs to be entered as a numerical val-
ue in the utility software OPM.
9.3.1.2 Sensor Specifications
a. Common parameters
·
Wavelength Range:
Within this range the sensor is calibrated and thus able to measure
with the specified measurement uncertainty.
·
Resolution
is the minimum detectable change of the measured parameter. The resolution
is always specified for a certain power meter type and bandwidth setting.
·
Measurement Uncertainty
states the measurement accuracy and is specified for the en-
tire wavelength range of the sensor. For some sensor types, an alternative value might be
specified for a partial wavelength range.
b. Photo Diode Sensors (S12xC, S13xC and S15xC Series)
·
Optical Power Range
specifies the minimum and maximum measurable power. Exceeding
the upper limit leads to sensor saturation and wrong measurement results. If pulsed signals
are measured, the pulse peak power must not exceed the maximum measurable power in
order to avoid saturation. Falling below the lower limit leads to increased measurement un-
certainty due to the increasing impact of noise.
·
Max. Average Power Density
must not be exceeded to avoid damages to the sensor. For
definition and calculation, please see section
.
·
Max. Pulse Energy
is an alternative specification to max. average power density, which
must not be exceeded. In case of the S15xC fiber sensors, the max. pulse energy density is
given. The reason is that fibers may have a very small beam diameter at the fiber tip, lead-
ing to high energy densities. For definition and calculation, please see section
.
c. Integrating Sphere Sensors (S14xC Series) and Thermal Sensors (S3xxC / S4xxC Ser-
ies)
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