Benchtop Optical Power Meters / Photometers and Radiometers

  • The UDT Instruments flexOptometer is a high-performance optical power meter designed to operate as either a stand-alone instrument or a computer-controlled, full-function photometric, radiometric or optical power measurement tool.
  • The FlexOptometer is the ideal instrument for measurement applications such as display, LED, laser power, fiber optics, strobe or signal measurements and more.
  • If your application requires measurement of low light levels, our C Series FlexOptometers offer ten times greater sensitivity than standard flexOptometer systems.
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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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Our flexoptometer is available with a single head or with up to four interchangeable detector heads for optimal flexibility.

Highly configurable via the USB, RS-232, RS-485, and IEEE-488.2 computer interfaces, it is easy to integrate into existing lab instrument architectures. The new light-measuring instrument offers faster, more accurate measurements than any previously available optometric system.

The electronic design is based on Gamma Scientific’s advanced performance, highly reliable, TIA-3000 measurement systems, which have become the primary working standards of several National Standards Labs. The transimpedance amplifier design gives very stable DC measurements down to the femtowatt (10-15 Watt) level. It also includes a pulse-integrator for pulsed energy measurements.

The instrument is designed as a laboratory grade optometer, with the robustness to operate flawlessly on even the most rigorous production lines. The optometer can be configured with Gamma’s extensive collection of optical detectors making it suitable for a wide variety of light measurement applications. Simply put, the flexOptometer is the ideal instrument for measurement applications such as display, LED, laser power, fiber optics, strobe or signal measurements and more.


  • Available in single and multi-channel configurations: Model S470 Single-Channel, Model S480 Dual-Channel, Model S490 Four-Channel
  • Touch screen back-lit LCD display
  • Configurable from one up to four measurement detector heads
  • USB, RS-232-, RS-485, and IEEE-488.2 computer interfaces
  • Low-light level measurements down to < 20 x 10-12 Watts or < 5 x 10-3 Lux
  • Silicon, photomultiplier, germanium and indium-gallium- arsenide (InGaAs) detectors available
  • Configurable with world-class photopic sensors (f1′ < 1%)



  • Display Measurements
  • LED Measurements
  • Fiber-optic Measurements
  • Laser Power Measurements
  • Strobe & Signal Measurements
  • Lamp Measurements
  • Night-Vision Testing
  • Customized Optics for Any Application




Eight Photometric/Radiometric RangesFour Integrate Ranges
Range-to-Range Linearity < 0.1% for most ranges (< 0.25% for most sensitive range)Range-to-Range Linearity < 0.1% for most ranges (< 0.25% for most sensitive range)
Sensitivity: 10-15; to 10-3 AmpsSensitivity: 10-14 to 10-3 coulomb
Resolution: 1×10-15 AmpsDecay Error: analog-approx. 0.01% / sec
Dark Current Suppression: 50 nA MaxDigital-holds reading indefinitely
Noise: < 5×10-15 Amps
Frequency Roll-off: < 10 Hz on most sensitive range
A-to-D Converter: 24-bit for each decade
Photometric/Radiometric Ranges
Radiometric Units*RangeSensor Configuration
Irradiance< 0.020 nanoWatts/cm² to 3000 microWatts/cm²
< 0.055 nanoWatts/cm² to 8000 microWatts/cm²
Model 221
Model 247
Irradiant Energy< 0.04 nanoJoules/cm² to 1.0 microJoules/cm² **
< 0.075 nanoJoules/cm² to 1.0 microJoules/cm² **
Model 221
Model 247
Radiant Flux< 0.020 nanoWatts to 3000 microWatts
< 0.055 nanoWatts to 8000 microWatts
Model 221
Model 247
Photometric Units*RangeSensor Configuration
Luminous Intensity< 0.0001 candelas to 10,000 candelasModel 424 CIE 127 Condition B Configuration
Illuminance< 0.005 lux to 500,000 luxModel 211
Luminance< 0.007 candela/m² to 1,200,000 candela/m²Model 2153
Illuminant Energy< 0.005 lux*seconds to 10 lux*seconds ***Model 211
Automatic/Manual ranging
Microprocessor Controlled Functions
High Voltage circuit for photomultipliers (300-1500 Volts)
Thermo-electric coolers for Sensor and filter stabilization
USB, RS-232, RS-485 and IEEE-488.2 Communications
Analog Output
Power Input: 12.0 volts DC
Operating Temperature Range: 0 to 50° C
Humidity: 0% to 95% RH non-condensing
Length (flexOptometer)13.00 inches (33.02 cm)
Width (flexOptometer)8.55 inches (21.72 cm)
Height (flexOptometer)5.22 inches (13.26 cm)
Sensors and Accessories
221Silicon Sensor (350-1100nm) 1cm2 active area211Photometric Sensor with Cosine Receptor (Illuminance)
222Silicon Sensor (200-400nm) 1 cm2 active area265Photometric Display Brightness Sensor (Luminance)
268UVALow Profile UVA Optimized Sensor Head (365 nm)268PLow-Profile Photometric Sensor with Cosine Receptor
268UVCLow Profile UVC Optimized Sensor Head (254 nm)2153Photometric Sensor with 13 degree FOV Lens (Luminance)
268BLUELow Profile Blue Optimized 450 nm Sensor424LED Photometric Sensor (CIE 127 Luminous Intensity)
RadiometricLaser Power
247Flat Response Sensor264Miniature Attenuated Laser Sensor Head
268RLow Profile Flat Response Sensor268LPLow Profile Laser Sensor Head
424RLED Radiometric Sensor (CIE 127 Radiant Intensity)
261Miniature Infrared Germanium Sensor (800-1750nm)
280Miniature Infrared InGaAs Sensor (800-1750nm)

*Ranges based on system configured with a 1 square centimeter silicon sensor and corresponding accessories
**Model 221 Maximum integrated energy 4.0 microJoules/cm² . Lower energy pulses will allow the average energy measurement to very accurate
**Model 247 Maximum integrated energy 10.5 microJoules/cm² . Lower energy pulses will allow the average energy measurement to very accurate
***Model 211 Maximum integrated energy 450 lux*seconds . Lower energy pulses will allow the average energy measurement to very accurate

Download Data Sheet

C Series flexOptometer

The C Series flexOptometers are thermo-electrically cooled optical power meter systems designed for high-sensitivity measurement applications.

The C Series includes an integrated controller that is compatible with UDT Instruments thermo-electrically cooled silicon and indium gallium arsenide (InGaAs) detectors.

C Series flexOptometers offer 10 times greater sensitivity than the standard flexOptometer products, making it the ultimate tool for measurement of low light levels.

The C1 model provides single stage cooling of the detector, and the C2 model provides dual stage cooling for applications that require a detector/filter combination. For high sensitivity applications, cooling of the detector and the filter is critical to accurate measurements.

The C Series flexOptometers have eight measurement ranges accessible through the front panel touch display or via serial and USB interfaces.

Options include high-accuracy photometric correction filters (f1’ ~0.8%), flat response filters, and NVIS compatibility filters with field-of-view lenses, making the C1 and C2 Series flexOptometers the standard for any light measurement requirement.

C Series flexOptometers allow for extremely low dark current levels <70 femtoamps; 70 x10-15 amps, at room temperature with the silicon detector) and excellent stability.

Standard calibrations are available for any configuration of the C1 and C2 series of flexOptometers from Gamma Scientific’s NVLAP accredited testing laboratory.


  • Temperature stabilized silicon and InGaAs detectors available covering 200 – 2600 nm
  • Temperature stabilized correction filters available
  • High accuracy photopic correction f1’~0.8%
  • NVIS compatibility filters and lenses
  • High sensitivity down to 10-13 watts or 10-6 lux
  • Eight decades of dynamic range
  • USB, RS-232 computer control



  • Display measurement photometry
  • LED radiometry
  • Night-vision compatibility measurements
  • Metrology lab primary standard detector
  • Customized optics available for any application




C Series flexOptometer Specifications
Gain1010 to 103 amps
RangeEight decades; touch front panel display readout in auto range or manual range. Computer
controlled output through serial RS-232 or USB protocol.
OutputDirect measurement output with your selected sensor calibration responsivity; i.e.: watts,
lux, cd/m2
LinearityRange-to-Range Linearity < 0.05%
Temperature Variation< 5 ppm (parts-per-million) per degree Celsius
Noise< 70 femtoamps; < 70 X 10-15 on range 1010; averaged system measurement
with a temperature stabilized silicon sensor
Frequency Roll-OffGain/Half Power Frequency

103 / 35 KHz
104 / 2200 Hz
105 / 220 Hz
106 / 100 Hz
107 / 100 Hz
108 / 100 Hz
109 / 48 Hz
1010 / 12 Hz

Length (Sensor)4.15 inches (10.5 cm)
Diameter (Sensor)2.5 inches (6.4 cm)
Length (flexOptometer)13.00 inches (33.02 cm)
Width (flexOptometer)8.55 inches (21.72 cm)
Height (flexOptometer)5.22 inches (13.26 cm)
Temperature StabilityShort term (1 hr.) < 0.001° C,
Long term (24 hr.) < 0.003° C
Bipolar Output Current+ 1.5 amp max
Maximum TEC Output Power12 watts
PowerExternal Switching Power Supply 12 Volts DC; 5.0 amps minimum
Download Data Sheet

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