Read-out

While the conventional Eddy current read out uses induced voltage and voltage amplification, the SQUID read out operates the probe as a magnetic flux transformer. This demands to minimize the resistivity of the pick up loop. 

Imaging plates are exposed similar to radiographic films. They are read out by a LASER-scanner to a digital image without any developing process. After optical erasing of the virtual picture the same IP can be used cyclic up to more than 1000 times. The life time is limited by the mechanical stability of the IP s. An IP consists of a flexible polymer carrier which is coated with the sensitive layer. This layer is covered with a thin transparent protective foil. 

Several tests have been performed with the biomedical systems of Fuji Film, the BAS 2500 and BAS 5000. The BAS25(K) is similar to the BAS2000 a flat bed scatmer which can read diverse IP-sizes up to 20 x 40 cm. The read out resolution can be set up to 100 pm or 50 pm. The BAS5000, is based on a new confocal read out optic which is... 

The specific advantage of this technique is its higher sensitivity than classical film radiography and the potential for automated image processing due to the digital read-out of the IP s. Former investigations have shown / / that the available IP s achieve the same contrast like NDT films with an IP type and scanner dependent unsharpness. 

Due to the pulsed radiation output of the LINAC the detectors and the detector electronics have to handle very high counting rates in very short periods. Therefore the detectors have to work in a mode, where the detector output is integrated for one or several beam pulses. For that purpose the crystals are coupled to photo- diodes. Their currents are read out and analysed by the electronic board, which has been developed for this special application. 

Therefore it is reasonable to prepare already the data acquisition for a three dimensional evaluation in cone-beam-technique by means of two-dimensional detectors. The system is already prepared to integrate a second detector- system for this purpose. An array of up to four flat panel detectors is foreseen. The detector- elements are based on amorphous silicon. Because of the high photon energy and the high dose rates special attention was necessary to protect the read-out electronics. Details of the detector arrangement and the software for reconstruction, visualisation and comparison between the CT results and CAD data are part of a separate paper during this conference [2]. 

In order to prepare the system for 3D-CT, it is not enough to integrate a second detector array. Besides this special attention has to be paid to the computer hardware, the synchronisation between object movement and the data read out as well as to the collimator of the LINAC. The collimator has been built with 4 tungsten blocks which can be moved individually m order to shape different sht sizes for 2D-CT as well as different cone angles for 3D-CT or digital radiography. 

Information may be stored in the architecture of the receptor, in its binding sites, and in the ligand layer surrounding the bound substrate such as specified in Table 1. It is read out at the rate of formation and dissociation of the receptor—substrate complex (14). The success of this approach to molecular recognition ties in estabUshing a precise complementarity between the associating partners, ie, optimal information content of a receptor with respect to a given substrate. 

Depending on the method of data read-out, respectively read-in/read-out, two systems are distinguished mechanooptical systems with usually disk-shaped media (optical disks), and purely optical systems with card-shaped media without moving parts (optical memory cards). 

Fig. 8. Principle of the magnetooptical read-out of domain patterns by the polar Kerr effect. The polarisation plane of the incoming laser beam is rotated clock- or counterclockwise according to the orientation (up or down) of the magnetic moments.

When used for superresolution, the laser beam is incident on b, which hides the domains in s. During read-out, b is heated and the domains in s are copied to b. The optical system sees only the overlap area between the laser spot and the temperature profile which is lagging behind, so that the effective resolution is increased. Experimentally it is possible to double the linear read-out resolution, so that a four times higher area density of the domains can be achieved when the higher resolution is also exploited across the tracks. At a domain distance of 0.6 pm, corresponding to twice the optical cutoff frequency, a SNR of 42 dB has been reached (82). 

Fig. 16. Maximum achievable signal-to-noise ratio (SNR) on read-out of different writable optical data storage systems as a function of the writing energy (laser power) (121). SQS = Organic dye system (WORM) PC = phase change system (TeSeSb) MO = magnetooptical system (GbTbFe). See text.

AH attempts to develop photopolymers or photothermoplasts suitable for fast and reversible recording and read-out of volume-phase holograms, however, have not gained commercial appHcation. The most important characteristics of materials for holographic information recording are Hsted in Table 4 (158). 

Another possible advantage of the PHB method is its potential multiplexing characteristics by synchronous recording and read-out, exceptional data transfer rates can be achieved. These high transfer rates are of equal importance in practical data technology as high storage densities. 

The initial measurement of electrical resistance must be made after considerable time. Phenomenological information has been determined based on the corrosion rate expected at what period of time to initiate readings of the electrical resistance. Since these values are based on experiential fac tors rather than on fundamental (so-called first) principles, correlation tables and lists of suggested thicknesses, compositions, and response times for usage of ER-type probes have developed over time, and these have been incorporated into the values read out of monitoring systems using the ER method. 

Frequently recalibrate and test all instruments, read-out devices, sensors and alarms. 

The test codes offer a good guide to use for the analysis. One te< nique to smooth the data is to screen off what appear to be bad poit T ide suggests one bad reading out of a set of four instruments at 2 f s cause to discard the point. Since the data are hard to acquire... 

Figure 4-241. Driller read-out display of the teleorienter in a zero tool face angle go straight, build angle position. (Courtesy Teledrift, Inc. [104]. ...

Linear polarization instruments provide an instantaneous corrosion-rate data, by utilizing polarization phenomena. These instruments are commercially available as two-electrode Corrater and three electrode Pairmeter (Figure 4-472). The instruments are portable, with probes that can be utilized at several locations in the drilling fluid circulatory systems. In both Corrater and Pairmeter, the technique involves monitoring electrical potential of one of the electrodes with respect to one of the other electrodes as a small electrical current is applied. The amount of applied current necessary to change potential (no more than 10 to 20 mV) is proportional to corrosion intensity. The electronic meter converts the amount of current to read out a number that represents the corrosion rate in mpy. Before recording the data, sufficient time should be allowed for the electrodes to reach equilibrium with the environment. The corrosion-rate reading obtained by these instruments is due to corrosion of the probe element at that instant [184]. 

Drawbacks of ion-selective electrodes ° Selectivity not always sufficient ° Direct read-out is less accurate with higher valent ions EMF-Drift may require frequent standardization... 

In more sophisticated instruments, the modern tendency is to replace the micro-ammeter by a digital read-out, and there is an increasing trend to use visual display units to show the results. Such instruments are controlled by microprocessors which may either show sequentially the successive operations which must be performed to measure the absorbance of a solution at a fixed wavelength or to observe the absorption spectrum of a sample alternatively the whole procedure may be automated. Such instruments will display the absorption spectrum on the VDU screen, and by linking to a printer, a permanent record is produced. 

The read-out systems available include meters, chart recorders, and digital display meters have now been virtually superseded by the alternative methods of data presentation. 

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