What Is a Spectral Irradiance Meter?
A spectral irradiance meter is an instrument that measures the irradiance of light from a source.
Irradiance refers to the incident radiant flux per unit area, essentially measuring the light energy reaching a given area from a light source. Thus, spectral irradiance meters measure irradiance in units of W/m² (watts per square meter). The required ambient brightness for human activities varies, and it’s not just about having bright surroundings.
The human eye is not suitable for measuring brightness due to its adaptability to surrounding light levels, making an objective evaluation challenging. Hence, the importance of using a spectral irradiance meter for objective quantification of ambient brightness.
Uses of Spectral Irradiance Meter
Spectral irradiance meters are essential in measuring the brightness in various settings, including offices, factories, and museums. They are crucial in environments like laboratories and factories where brightness levels must be strictly controlled, sometimes even regulated by law.
Additionally, regulations such as the Fire Service Law mandate specific illuminance levels for audience guide lights in movie theaters and similar venues, necessitating the use of spectral irradiance meters to ensure compliance.
Principle of Spectral Irradiance Meter
Spectral irradiance meters use elements like photoresistors or photodiodes to detect electromagnetic waves. Photoresistors change their electrical resistance in response to electromagnetic waves, while photodiodes convert these waves into electric current.
Using different elements, such as photodiodes, allows the measurement of both radiant illuminance (including non-visible electromagnetic waves) and visible illuminance. These measurements serve various purposes and are vital in different contexts.
Other Information on Spectral Irradiance Meter
1. Difference Between Spectral Irradiance Meter and Illuminance Meter
An illuminance meter, unlike a spectral irradiance meter, is designed to detect only light within the human-visible wavelength spectrum. Radiant illuminance includes both visible light and electromagnetic waves like ultraviolet and infrared rays, essential in certain environments.
For instance, to measure the effect of ultraviolet rays on chemical substances, which may undergo decomposition, a spectral irradiance meter is indispensable.
2. Difference Between an Irradiance Meter and a Spectral Irradiance Meter
The key distinction lies in their spectral measurement capabilities. An irradiance meter calculates irradiance as a total of the measured wavelength range, whereas a spectral irradiance meter provides detailed output for each wavelength within the range at specific resolutions (e.g., 1 nm increments).
Spectral irradiance meters can also function as irradiance meters and evaluate the color rendering properties of light sources, an important aspect in settings like museums where high color rendering LEDs are increasingly required.