Ophir Optronics Ltd QSR Manuel D’Utilisation
Appendix B – Calibration, Traceability, and Recalibration
Ophir Photodiode Heads
Note: For units that have different calibration factors (e.g., CO2, YAG, or
VIS), select the correct laser in the main Configuration Area before
calibration.
calibration.
Note: Changing energy calibration at one wavelength will affect all other
wavelengths proportionately. However, changing the energy
calibration will not change the power calibration.
calibration will not change the power calibration.
Ophir Photodiode Heads
This section discuses calibration of Ophir photodiode heads.
Factory Calibration of Photodiode Heads
Photodiode detectors are inherently very linear but also have a large variation in
sensitivity with wavelength. In addition, the Ophir model PD300 is equipped
with both a built in filter and removable filter to allow measurement of higher
powers without detector saturation. These filters also have a transmission that
depends on wavelength. Therefore, the PD300 has a built in calibration
adjustment for wavelength.
sensitivity with wavelength. In addition, the Ophir model PD300 is equipped
with both a built in filter and removable filter to allow measurement of higher
powers without detector saturation. These filters also have a transmission that
depends on wavelength. Therefore, the PD300 has a built in calibration
adjustment for wavelength.
The sensitivity of various Ophir photodiode sensors can vary from one to another
as well as with wavelengths. Therefore, Ophir photodiode detectors are
individually calibrated against NIST traceable standards over the entire operating
range of wavelengths for both filter out and filter in. The calibration curve is
normalized to the correct absolute calibration at 632.8 nm using a HeNe laser
against a reference meter traceable to NIST.
as well as with wavelengths. Therefore, Ophir photodiode detectors are
individually calibrated against NIST traceable standards over the entire operating
range of wavelengths for both filter out and filter in. The calibration curve is
normalized to the correct absolute calibration at 632.8 nm using a HeNe laser
against a reference meter traceable to NIST.
The spectral sensitivity curve of the detector and the spectral transmission curve
of the filters are fed into the head EEROM. This information is used to set the
gain to the proper value at wavelengths other than the wavelength at which the
instrument was calibrated. When the user selects his wavelength on the
instrument, the correction factor for that wavelength is applied.
of the filters are fed into the head EEROM. This information is used to set the
gain to the proper value at wavelengths other than the wavelength at which the
instrument was calibrated. When the user selects his wavelength on the
instrument, the correction factor for that wavelength is applied.
Linearity and Accuracy of Photodiode Heads
Since the instruments are calibrated against NIST standards, the accuracy is
generally ±2% at the wavelength that the calibration has been performed. The
maximum error in measurement will be less than the sum of:
generally ±2% at the wavelength that the calibration has been performed. The
maximum error in measurement will be less than the sum of:
calibration accuracy + linearity + inaccuracy due to errors in the
wavelength curve + variations in gain with temperature
wavelength curve + variations in gain with temperature
The linearity of the photodiode detector is extremely high and errors due to this
factor can be ignored. Table B-2 shows the maximum error due to the factors
described here.
factor can be ignored. Table B-2 shows the maximum error due to the factors
described here.
StarLab User Guide
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