CIE Interlaboratory Comparison of Measurements of Photocell Spectral Sensitivity

Area of Science:

• Photometry and Radiometry
• Optical Measurements

Background:

• Accurate spectral sensitivity measurements of vacuum photocells are crucial for reliable photometric applications.
• The CIE Photometry and Radiometry Committee (TC-1.2) initiated an interlaboratory comparison to assess measurement consistency.

Purpose of the Study:

• To summarize the results of an interlaboratory comparison of relative spectral sensitivity measurements for vacuum photocells.
• To identify sources of error and assess the precision of these measurements across multiple laboratories.

Main Methods:

• Nine laboratories participated, each measuring the relative spectral sensitivity of two vacuum photocells.
• Measurements were performed with and without V(lambda) correction filters.
• Data were corrected for cell spectral sensitivity drift.

Main Results:

• Standard deviation for measurements without filters was <2% between 450-620 nm, increasing to 5% at 390 nm and 690 nm.
• Standard deviation for V(lambda) corrected cells was <2% between 490-600 nm, increasing to 5% at 475 nm and 660 nm.
• Wavelength and bandwidth errors were identified as probable primary sources of the largest measurement deviations.

Conclusions:

• Interlaboratory comparison demonstrated good precision for relative spectral sensitivity measurements of vacuum photocells within specific wavelength ranges.
• Careful control of wavelength and bandwidth is essential to minimize errors in spectral sensitivity measurements.