Photometer amplifier

Fig. 10-14. CFA manifold for nitrate with LED-photometer and twin photometer amplifier (Institut fiir...

The photometer is adequately described in Figure 3-2. In the phosphor-photoelectric detector (2.10), the x-ray beam strikes a silver-activated zinc sulfide phosphor to produce blue-violet light that is changed by the multiplier phototube (Type 931-A) into an electric current that is amplified and read on a suitable micro- or milliammeter. A stable power supply for both x-ray tube and detector circuit are essential, as is clear from the circuit diagrams.10... 

Figure 11 illustrates an SEC separation of a sample of 3-conponent polystyrene mixture with the dual concentration and viscosity detectors of Figure 10. The top trace shows the concentration elution profile of the SEC separation as detected by a uv-photometer. The bottom trace records the same SEC separation, except with the viscometer signal from the log-amplifier output.

The luminous intensity for various types of illuminating and tracer flares is measured by using a photometer which mainly consists of two parts-optical part (mainly photovoltaic detector) and electronic part (consisting of amplifier, digital meter, computer with interface card and printer). The experimental set-up is shown in Figure 5.5. 

The flame photometer consists essentially of an atomizer, a burner, some means of isolating the desired part of the spectrum, a photosensitive detector, sometimes an amplifier and, finally, a method of presenting the desired emission, whether by galvanometer, null meter, or chart recorder. 

Since this is a book concerned primarily with applications, no further details are given concerning instrumentation. The reader is referred to Alpert et al. (1970), in which are discussed an optical diagram of a double-beam spectrophotometer operating variables (resolution, photometric accuracy) components of infrared spectrophotometers (sources, types of photometers, dispersing elements, detectors, amplifiers, and recorders) special operating features, such as optimization of scan time and available instruments and their specifications. The books by Martin (1966), Conn and Avery (1960), and Potts (1963), and the chapter by Herscher (1966) are also recommended for details on some of these topics. 

After 1945 the development of flame photometers or flame attachments for existing equipment was rapid. The Beckman Company introduced a flame attachment for their DU spectrophotometer in 1948 and subsequently introduced their very popular total-consumption burner. The signal was detected by either a phototube or photomultiplier with a dc amplifier... 

Photometer, Fig. 2 DNA microarrays. The probes are complementary fragment oligonucleotides, of target DNA or mRNA spotted onto the microarray surface. This type of array is typically hybridized with target cDNAs that are labeled with fluorophores. The samples are amplified by PCR and hybridized to the microarray and then scanned in... 

Fig. 84. Schematic diagram of laboratory turbidity photometer LTP 3 1) = Stabilizer for lamp 2) = Optical system 3) = Lamp 4) = Particles causing turbidity 5) = Cuvette 6) = Optical system 7) = Measuring cell 8) = Compensating amplifier 9) = Data display, recording and control unit 10) = Data output...

A basic calibration procedure is required to adjust the spectrophotometer amplifiers to convert the two measured light intensities, I (sample) and /q (optical or electronic reference), into the correct solution of the term log foil), Le., the absorbance as defined by Beer-Lambert s law (see Section 10.2). Mechanical or electronic simulation of an intensity Z = 7o must result in a zero photometer output. The linearity of the absorbance output should be checked by measuring a standard dilution sequence (see Section 10.2.4). 

Photometer Tungsten lamp Attenuated light beam Filter Photodiode Electrical current Amplifier, di tizer, LED display... 

Many mixlern photometers and spectrophotometers are based on a double-beam design. Figure 13-13b illustrates a double-beam-in-space instrument in which two beams are formed in space by a V-shape mirror called a beamspHuer. One beam passes through the reference solution to a pholodetector, and the second simultaneously traverses the sample to a second, matched detector. The two outputs are amplified, and their ratio (or the logarithm of their ratio) is determined electronically or by a computer and displayed by the readout device. With manual instruments, the measurement is a two-step operation involving first the zero adjustment with a shutter in place between selector and... 

The ideal flame photometer is one which comprises a monochromator with motorised wavelength control, and to which can be attached any type of source unit. The detectors should be capable of responding to emission from 2,000A to 8,000A, and these should feed into an amplifier of wide sensitivity range. The output can be either read on a meter or passed into a recorder. This opinion is not intended to decry the use of simple equipment, but indicates what is required for the estimation of a large number of elements in all kinds of samples. 

The instrument used in the author s laboratory is an absolute photometer with chopper and lock-in amplifier, yielding absolute Rayleigh ratios (9)- Photographic recording of light scattering patterns which has proven to be of value for the characterization of crystalline polymer films usually fails for networks - whether dry or swollen - because of the much lower levels of scattering. 

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