Paul Meunier's electrophotometer (1937)

Designed by biochemist Paul Meunier and produced by Jobin Yvon, this photometer was the first instrument to use barrier layer photocells to perform absorption and fluorescence measurements in the visible spectrum. Initially produced in small volumes, more than 3,000 units were sold. The device is used both in biology, particularly for the determination of small quantities of vitamin D, and in oceanography to measure the phosphate, nitrate and silica content of seawater.