Designed and configured for all LED measurement requirements, the portable S-741 LED optometer from UDT Instruments features microprocessor control and three measurement data-presentation options: direct display measurement with analog bar, RS-232C computer interface, and analog voltage input. The unit is equipped with a silicon photometric detector and LED holding sockets for many common LED types. All the sockets are designed to meet the recommended CIE Publication 127, Conditions A and B, for measurements of the luminous intensity (candelas) of LEDs. The instrument is suitable for luminous or radiant intensity measurements, tunnel brightness, total luminous or radiant flux measurements, device brightness, signal brightness, and equipment and device illumination measurements. The device includes an optional integrating sphere designed specifically for total luminous or radiant flux (lumens or watts) LED measurements. The system comes with a touch keypad and backlit LCD for easy read-out. The NIST-traceable (National Institute of Standards) factory calibration makes it easy to configure for a wide variety of applications, including illuminance, irradiance and fiber-optic measurements. The optometer has a rechargeable NiMH battery.