A Photomechanical Device for Triggering Digital Output on a GE Spectrophotometer

Most applications of modern spectrophotometry demand that spectrophotometric measurements be recorded on media suitable for direct use by data processing equipment. This paper describes a photomechanical method for actuating the readout command for an old model GE recording spectrophotometer. This instrument has nonlinear wavelength representation in the near ultraviolet and near infrared. The method involves an opaque disk having a direct one-to-one rotation relation with the wavelength drive. The disk contains three sets of small holes on the circumference of concentric circles which represent the near ultraviolet, visible, and near infrared regions of the spectrum. The accurate angular separation of these holes, along with a photodiode and lamp which are aligned for each set of holes, makes available a selection of these three ranges and automatically actuates the readout command in the control chassis at 10-nm intervals for all wavelength ranges. The data are then punched into cards by an IBM 526 summary punch. The option of taking data at 5-nm intervals is provided by a suitable second disk.