Radiometers are used to measure the intensity of electromagnetic radiation (e.g., UVC, UVB, UVA, Vis, and IR). They are univariate devices that do not distinguish between light of different wavelengths. In addition to wavelength range, radiometers carry specifications such as sensor diameter, power range, accuracy, resolution, operating temperature range, and humidity range. The wavelength range specifies the detection range for radiometers. The sensor diameter measures the active part of the sensor. Power range is the power per unit area. Radiometer accuracy is usually given as a percentage. The resolution of the detector is a measure of radiometer sensitivity. Operating temperature and humidity range are also important specifications to consider when selecting radiometers.
Radiometers differ in terms of display type. Choices include needle indicator, numeric, alphanumeric, and video. A needle indicator is a face upon which an analog measurement is registered, typically by means of graduations and a pointer. Radiometers with a numeric indicator display the output in whole numbers, usually in digital form. Devices with an alphanumeric indicator display the output as both letters and numbers, generally in digital form. Radiometers with video displays may use a cathode ray tube (CRT), liquid crystal display (LCD), or other multi-line form.
Mounting styles for radiometers are often listed as handheld, portable, lab or benchtop, and in-situ or field. Handheld radiometers are designed to be used while held in only one hand. Portable radiometers have handle, cases, wheels or casters for ease of movement; however, they are not necessarily handheld. Lab radiometers or benchtop radiometers are designed to sit atop a laboratory benchtop. These devices are not appropriate for field measurements. By contrast, in-situ or field radiometers are designed for use outside of a laboratory, in a field setting.
Features for radiometers may include a low battery indicator and user-selectable ranges. Devices with low battery indicators usually have a built-in indicator that reads the level of the battery’s charge. These indicators also notify the user when battery levels are low, typically by means of a visual or audible alarm. Devices that have selectable wavelength ranges are also available from a variety of radiometer suppliers.