UDT Instruments

For over 40 years UDT Instruments, a Gamma Scientific company, has been trusted by the world’s leading organizations to provide accurate light measurement systems.

UDT Instruments manufactures precision photometers, radiometers, colorimeters and photosensors for optical measurement applications.

UDT Instruments designs the most accurate photometric filters in the world, with an unsurpassed ability to match the human eye’s sensitivity to color and light intensity. Each sensor includes a NIST-traceable calibration.

High-performance optometers from UDT Instruments can be combined with our integrating spheres and detectors to create complete photometric and radiometric test systems with industry leading accuracy.

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System Configuration Guide

Learn how to configure a photometer or radiometer system to meet your testing requirements with this free guide from Gamma Scientific.


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Guide to Photometry

What’s in the Guide?

  • Definitions of the most important terms in photometry
  • Photometric to radiometric conversion factors
  • How to specify a photometer system
  • Photometric quantity units, symbols and abbreviations


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Guide to Radiometry

What’s in the Guide?

  • Definitions of the most important terms in radiometry
  • How to specify a radiometer system
  • Radiometric quantity units, symbols and abbreviations
  • Calibration by transfer of standards


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Light Meters - Photometers and Radiometers

S470 and ingaas detectors

We offer an extensive selection of photometers, lux meters, luminance meters, illuminance meters and optical sensors to meet your photometric test and measurement needs.

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Light Meters - Optical Power Meters



Combining our optometers, radiometric sensors and accessories, with our state-of-the-art calibration facilities, our applications engineers can assemble and configure custom radiometer systems for nearly any project.

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Reference Standard Detectors

TIA-3000 reference standard detector


The TIA-3000 Measurement Systems are detector-based absolute standards for a variety of high-accuracy measurements. Off-the-shelf configurations include thermo-electrically cooled silicon and indium gallium arsenide (InGaAs) detectors.

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UDTi photometric sensors are designed with advanced photometric filters to simulate the response of the human visual system and match the spectral response of a standard observer. When coupled with an optometer, photodetectors are used to measure luminous flux (lm), illuminance (lux), luminous intensity (cd) and luminance (cd/m²).

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Transimpedance Amplifiers

Transimpedance Amplifier


The UDT Tramp is a transimpedance amplifier (current-to-voltage) instrument which provides a low input impedance to accurately measure the short circuit current of phototransducers such as silicon and germanium photodetectors, vacuum photodiodes and photomultiplier tubes.

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Position Sensing



Our extensive selection of optical position sensors, position amplifiers/indicators and accessories allows our applications engineers to assemble and configure a tremendous variety of position-sensing systems.

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The History of UDT Instruments

The evolution of UDT Instruments can be traced to 1967, when a small group at United Detector Technology (UDT) began manufacturing the first commercially available transimpedance amplifiers for planar-diffused and Schottky barrier silicon photosensors. From there, the group went on to pioneer leading-edge technology for photometers, radiometers, fiber optic power meters, and optical position sensing instruments. By the time the 1980s rolled around, this innovative and highly successful group grew into an autonomous entity known as UDT Instruments (UDTi).

The momentum generated by UDTi’s precision photometric instruments ultimately spurred the company to develop an inventive handheld CRT colorimeter for the growing television and computer peripherals markets. UDTi’s SLS 9400 colorimeter has strengthened the company’s position as a leader in precision electro-optic instrumentation. We have continually improved on the SLS 9400, allowing it to continually meet the stringent demands of display calibrations as the industry has transformed into flat-panel and projection displays. Today, UDTi is poised and ready to pursue even greater technological excellence with only one goal in mind: to meet or exceed the ever-changing needs of its customers worldwide.

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