uNIT-Watt Radiometric Meter - General Purpose

This Watt Meter System includes our standard radiometric sensor that can be combined with a wide range of accessories including optical filters, integrating spheres and spacers.  It provides measurement of radiant flux in units of Watts of mW.

Combined with our highly popular S471 portable photometer, the system provides simple and precise measurements.  The package includes a battery charger and necessary connector cables.

Under the UDT Instruments brand, Gamma Scientific manufactures a broad range of precision photometers, radiometers, colorimeters and photosensors for optical measurement application.

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Precision-matched Measurement Solutions

S471 Optical Power Meter

  • High Accuracy Measurements
  • Programmable Average Readings in Low Pass or Boxcar Average
  • High Speed Update Rate
  • Optional USB to Serial Bridge Converter
  • Long Battery Lifetime or Use External Power

221 Sensor

  • Standard Calibration in W or mW at User-Specified Wavelength
  • Dynamic Range from 5 x 10-11 to 2.4 x 10-3 W
  • Calibration Range from 350 to 1100 nm
  • High Linearity, Low Noise
  • Compatible with a Wide Range of Accessories


Update rates

RS-232 (Display Enabled) > 2 times per second

RS-232 (Display Disabled) up to 53 times per second


Direct Measurement RS-232 interface and analog output

Analog Output Scale

± 1, 2 or 4 VDC

Communication Rate

9600 Baud

Operational Battery Life

32 Hours with backlight on

24 Hours with backlight off

Operating Temperature

10 to 60° C

Storage Temperature

-20 to 35° C for up to 1 year

External Power Source

100 to 240 VAC at 1A, 50 to 60 Hz or

12 VDC at 3.3 A, 40 W max

Internal Power Source

Rechargeable integral battery pack

5 NiMH AA, 1800 mAHr batteries

Calibration Capacity

9 Continuous or 50 single-point

Calibration Traceability

Traceable to NIST

Relative Humidity

Up to 99% (non-condensing)



Standard Calibration(s)

Optical Power in mW at user-specified wavelength

Dynamic Range

5.0 x 10-11 to 2.4 x 10-3 W

Standard Calibration Range

350 to 1100 nm in 10 nm steps

Typical Response

5.1 x 10-1   A/W @ 980 nm


High Linearity, Low Noise

Sensor Active Area

1 cm2



Specifications are subject to change without notice