Calibration, Maintenance, and Troubleshooting
1919-R User Manual
98
12.3
Calibration of Photodiode Sensors
12.3.1
Method of Factory Calibration
The sensitivity of various Newport Photodiode sensors can vary from one to another as well as
with wavelengths. Therefore, Newport 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, as well as the spectral transmission curve of the
filters, is fed into the sensor EEROM, and this information is used to set the gain to the proper
value at wavelengths other than the wavelength the instrument was calibrated. When the user
selects his wavelength on the 1919-R, the correction factor for that wavelength is applied.
12.3.2
Accuracy of Calibration
Since the instruments are calibrated against NIST standards, the accuracy is generally ±2% at the
wavelength the calibration has been performed. The maximum error in measurement will be less
than the sum of the calibration accuracy, linearity, inaccuracy due to errors in the wavelength
curve and variations in gain with temperature. The linearity of the Photodiode detector is
extremely high, and errors due to this factor can be ignored. The maximum error due to the above
factors is listed in
Table
12-1 Maximum Error as a Function of Wavelength and Filter
Model
918-UV-OD3R
818-UV/DB
918D-SL-OD3R
818-SL/DB
918D-IR-OD3R
818-IR/DB
918D-IG-OD3R
818-IG/DB
Calibration
Uncertainty
Without
Attenuator
4%@200-219nm
2%@220-349nm
1%@350-949nm
4%@950-1100nm
1%@400-940nm
4%@941-1100nm
2%@780-910nm
2%@911-1700nm
4%@1701-1800nm
2%@800-900nm
2%@901-1650nm
Calibration
Uncertainty With
Attenuator
8%@200-219nm
2%@220-349nm
1%@350-949nm
4%@950-1100nm
1%@400-940nm
4%@941-1100nm
5%@780-910nm
2%@911-1700nm
4%@1701-1800nm
5%@800-900nm
2%@901-1650nm
