- a device for measuring intensity of radiation, especially that of the sun.
Origin of actinometer
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for actinometer
A Johnson's actinometer is very useful to time the exposure.Photogravure
Henry R. Blaney
We can, however, by chemical means arrive at an exact estimate of the active power, and for this purpose an actinometer is used.
You may sometimes find that the actinometer indicates a very different exposure from what the eye would lead you to expect.
The actinometer indicated an exposure of thirty seconds where in good light one would be right.
For judging long exposures, the use of an actinometer (issued in many inexpensive forms) is helpful.
- an instrument for measuring the intensity of radiation, esp of the sun's rays
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
- Any of several instruments used to measure radiation, such as a pyrheliometer.
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