a device for measuring intensity of radiation, especially that of the sun.
Related formsac·tin·o·met·ric [ak-tin-oh-me-trik, ak-tuh-noh-] /ækˌtɪn oʊˈmɛ trɪk, ˌæk tə noʊ-/, ac·tin·o·met·ri·cal, adjectiveac·ti·nom·e·try, noun
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for actinometer
Historical Examples of actinometer
A Johnson's actinometer is very useful to time the exposure.
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.
British Dictionary definitions for actinometer
Derived Formsactinometric (ˌæktɪnəʊˈmɛtrɪk) or actinometrical, adjectiveactinometry, noun
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.
The American Heritage® Science Dictionary
Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.