This Optek C4101 Control 4000 Photometric Converter with AS16 Probe Sensor is in great condition and was removed from a working environment. This unit came from a local lab that had surplus lightly used equipment. Unit shows only slight aesthetic signs of normal use. We urge customers to view all photos as they show overall condition, included accessories and functionality. Please Note: Second photo in listing shows screen after controller was powered on. We are unsure if this is an error message or simply a reboot message. We will be happy to perform any test to insure functionality as well as provide additional photos. Please feel free to contact us with any questions. The Control 4000 is a powerful, microprocessor-based photometric converter. The advanced modular design enables precision process monitoring and control. The flexible C4000 is designed for optek ultraviolet (UV), visible (VIS), near-infrared (NIR) absorption-based and scattered-light based sensors. Sensor AF16 VIS and NIR Absorption, Single Channel Concentration and Color Measurement FOR ADDITIONAL INFORMATION PLEASE VISIT LINK BELOW https://www.optek.com/pdf/productinformation/optek-Brochure-1005-1001-02-PI-C4000-C8000-US.pdf (If link is no longer available please contact us for copy of PDF)