Crystal Readout

Display The representation of text and images on a cathode-ray tube, an array of hght-emitting diodes, a liquid-crystal readout, or another similar device. 

A crystal material is excited by the force imposed on it by an internal I v mounted mass. A voltage is produced by the crystal proportional to accel eration. This voltage is then amplified by a charge amplifier type signal conditioner from whence the signal can be transmitted long distance. (1.000 feet is not uncommon) to the monitor/readout unit. It is calibrated in terms of gravitational units (g), which are proportional to force. Force is ttnc of the most reliable indicators of equipment distress. 

Answer An electronic temperature monitor could be equipped with a bar-code liquid crystal display which could be read by a portable bar-code reader. These devices have a memory so several readings may be taken before they are readout over a telephone modem to a data logging computer. The simplest way to read the acid type would be to post a label that is bar-coded to indicate the acid type. Tire acid quantity could be indicated by an acid level gage using a bar-code display of the level. The aluminum quality could be indicated by displaying a label in bar-code. The amount of aluminum could be determined by weight using a bar-code readout on the scales. 

Figure 3.24 — Typical system for piezoelectric crystal detector incorporating reference (C,) and test (CJ crystal sensors individually held in oscillating circuits (Or and 0 respectively) serviced by separate frequency counters (FC, and FCj, respectively) interfaced to a common microprocessor or other readout device. (Reproduced from [167] with permission of the American Chemical Society).

Endpoint assays such as proliferation or cytotoxicity assays are routinely used for functional assessments. For these assessments, primary cells, transformed cells, or cells transfected with the target receptor are exposed to range of concentrations of the test article. Proliferation or cytoxicity is then measured using a variety of methods such as crystal violet vital dye staining, MTT/MTS incorporation, or a luminescence readout like ATP lite. In addition, assays that analyze phosphorylation of specific transcription factors, or release of specific cytokines and chemokines, are also common. Figure 9.5 illustrates the measure of functional consequences of receptor-test article interaction by quantifying cytokine release. Cells from the species under evaluation were cultured in the presence of serial dilutions of the test article or control reagents, and supernatants harvested for determination of cytokine levels by ELISA (i.e.,... 

Figure 1.5 Commercial deposition thickness monitor (courtesy Sloan, Inc.) employing AT-cut, 5-MHz quartz crystal in the sensor head at left. Digital control and readout equipment is shown at right.

FIGURE 1.23 Communicating with a conducting polymer PPy/Cl in solution (a) cyclic voltammetry—a plot of current flow versus the electrical (potential) stimulus applied (b) the electrochemical quartz crystal mircobalance readout—mass polymer versus electrical (potential) stimulus applied (c) the resistometry readout—resistance of the polymer versus the electrical (potential) stimulus applied. (Printed with permission from Materials Science Forum, Vol. 189-190, Characterization of conducting polymer-solution interfacial processes using a new electrochemical method, A. Talaie, G. G. Wallace, 1995, p. 188, Trans Tech Publications, Switzerland.)... 

Compact chemical sensors can be broadly classified as being based on electronic or optical readout mechanisms [28]. The electronic sensor types would include resistive, capacitive, surface acoustic wave (SAW), electrochemical, and mass (e.g., quartz crystal microbalance (QCM) and microelectromechanical systems (MEMSs)). Chemical specificity of most sensors relies critically on the materials designed either as part of the sensor readout itself (e.g., semiconducting metal oxides, nanoparticle films, or polymers in resistive sensors) or on a chemically sensitive coating (e.g., polymers used in MEMS, QCM, and SAW sensors). This review will focus on the mechanism of sensing in conductivity based chemical sensors that contain a semiconducting thin film of a phthalocyanine or metal phthalocyanine sensing layer. 

The first reported gas phase biosensor was in fact an enzyme-based Pz sensor [58]. Crystals coated with formaldehyde dehydrogenase were used to linearly detect formaldehyde in air from lOppb to 100 ppm. A portable version of the sensor was also developed. The battery-operated instrument contained a digital readout and miniature sampling pump. Weighing just 3 lbs it was used in field for on site analysis. 

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