Upgrading a High Performance Spectrophotometer

Abstract

A spectrophotometer system was updated with a new computer and control circuitry to measure qualitative and quantitative characteristics of agricultural products between the ultraviolet and near infrared (NIR) regions of the electromagnetic spectrum. This single beam instrument, along with its computer, has a wavelength repeatability of 0.005 nm. This performance is required for proper system response compensation in a single beam system. Analog electronics are kept to a minimum by early conversion of the signal with a 10-μs 16-bit analog-to-digital (A/D) converter. A fast response real-time computer is required to service the A/D, wavelength drive and optical chopper. Herein, the development and selection of computer interfaces, data collection techniques and performance characteristics of this laboratory spectrophotometer system are described. The system is regularly used as the development tool in investigating new measurement techniques on agricultural products. It is also used to evaluate optical filters and other spectrophotometric systems.