Transducers photoelectric

Multiplying the transmittance by 100 gives the percent transmittance (%T), which varies between 100% (no absorption) and 0% (complete absorption). All methods of detection, whether the human eye or a modern photoelectric transducer, measure the transmittance of electromagnetic radiation. 

Fuel cell polymer battery photoelectric cell capacitor Storage element liquid crystal display device electrochromic display device electrochemiluminescence device photoelectric transducer Biosensor ion sensor detector in HPLC and FIA gas sensor voltam-metric indicator electrode reference electrode... 

Optical detection can also be used in p-jump relaxation studies. One of Ils major attributes is that one can study systems other than ionic ones, which IS not the case with conductivity detection. Changes in optical properties can be followed rapidly und with fine sensitivity utilizing photoelectric transducers... 

Fluorescence detectors for HPLCare similar in design to the fluorometers and spectrofluoromeiers described in Section 15B-2, fn most, fluorescence is observed by a photoelectric transducer located at W to the excita lion beam. The simplest detectors use a mercury excitation source and one or more filters to isolate a band of emitted radiation. More sophisticated instruments are based on a xenon source and use a grating monochromator to isolate the fluorescence radiation. I.ascr-induced fluorescence is also used because of its sensitivity and select iviiy. 

Most modern instruments rely on photoelectric transducers, detection devices that convert photons into an electrical signal. Photoelectric transducers have a surface that can absorb radiant energy. The absorbed energy either causes the emission of electrons, resulting in a photocurrent or moves electrons into the conduction band of a solid semiconductor, resulting in an increase in conductivity. There are several common forms of these detectors including barrier layer cells, photomultiplier tubes, and semiconductor detectors. 

Spectrometric methods are a large group of analytical methods that arc based on atomic and molecular spectroscopy. Spectroscopy is a general term for the science that deals with the interactions of various types of radiation with matter. Historically, the interactions of interest were between electromagnetic radiation and matter, but now spectroscopy has been broadened to include interactions between matter and other forms of energy. Examples include acoustic waves and beams of particles such as ions and electrons. Spectrometry and spectrometric methods refer to the measurement of the intensity of radiation with a photoelectric transducer or other type of electronic device. 

FIQURE 7-27 Relative response of various types of photoelectric transducers (A-G) and heat transducers (H. I) A, photomultiplier tube B, CdS photoconductivity C, GaAs photovoltaic cell D, CdSe photoconductivity cell E, Se/SeO photovoltaic ceii F, siiicon photodiode G, PbS photoconductivity H, thermocouple /, Golay cell. (Adapted from R W. Druse, L. N. MoGlauchlih, and R. B. Quistan, Elements of Infrared Technology, pp. 424-25, New York Wiley, 1962. Reprinted by permission of John Wiley Sons Inc.)... 

We use the term colorimeter to designate an instrument for absorption measurements in which the human eye serves as the detector using one or more color-comparison standards. A photometer consists of a source, a filler, and a photoelectric transducer as well as a signal processor and readout. Note that some scientists and instrument manufacturers refer to photometers as colorimeters or photoelectric colorimeters. Filter photometers are commercially available for absorption measurements in the ultraviolet, visible, and infrared regions, as well as emission and fluorescence in the first two wavelength regions. Photometers designed for fluorescence measurements arc also called fluorometers. 

A spectrometer is an instrument that provides information about the intensity of radiation as a function of wavelength or frequency. The dispersing modules in some spectrometers are multichannel so that two or more frequencies can be viewed simultaneously. Such instruments are sometimes called polychromators. A spectrophotometer is a spectrometer equipped with one or more exit slits and photoelectric transducers that permit the determination of the ratio of the radiant power of two beams as a function of wavelength as in absorption spectroscopy. A spectrophotometer for fluorescence analysis is sometimes called a speciroftttorometer. 

Figure 7-27 shows the relative spectral response of the various kinds of transducers that arc useful for UV, visible, and IR spectroscopy. The ordinate function is inversely related to the noise of the transducers and directly related to the square root of its surface area. Note that the relative sensitivity of the thermal transducers (curves H and /) is independent of wavelength but significantly lower than the sensitivity of photoelectric transducers. On the other hand, photon transducers are often far from ideal with respect to constant response versus wavelength. 

After the appearance of photoelectric transducers in the 1930s, multichannel photoelectric spectrometers became commercially available. 

Murase, M., a. Usuki, Y. Kitahara Polymeric Photoelectric Transducer. Jpn. Kokai Tokkyo Koho JP 61125090 A2, 12 Jun 1986. 

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