Level detector, operational

The fuse is a level detector and is both the sensor and the interrupting device. It is installed in series with the equipment being protected, and it operates by nieltiiig a fusible eleliieiit in response to the current flow. 

As GC is not only used as a separation medium but also as an analytical technique detection has an important function. Even if the column tolerates high-solute levels, detector requirements may determine the best injection technique or they may dictate adding a sample dilution step before injection to bring injected quantities within the optimal operating range. GC instruments accommodate an extremely wide range of solute concentrations. Minimum and maximum solute... 

This module describes the construction, operation, and failure modes for various types of level detectors and indication circuits. 

The analytes separated on GC column are determined by a halogen-specific detector, such as an electrolytic conductivity detector (ELCD) or a microcoulo-metric detector. An ECD, FID, quadrupole mass selective detector, or ion trap detector (ITD) may also be used. A photoionization detector (PID) may also be used to determine unsaturated halogenated hydrocarbons such as chlorobenzene or trichloroethylene. Among the detectors, ELCD, PID, and ECD give a lower level of detection than FID or MS. The detector operating conditions for ELCD are listed below ... 

Figure 8 illustrates a conductivity probe level detection system. It consists of one or more level detectors, an operating relay, and a controller. 

The conductivity probe consists of one or more level detectors, an operating relay, and a controller. When the liquid makes contact with any of the electrodes, an electric current will flow between the electrode and ground. The current energizes a relay which causes the relay contacts to open or close depending on the state of the process involved. The relay in turn will actuate an alarm, a pump, a control valve, or all three. 

The designs of tank farm level detectors include (1) wire-guided float, (2) servo-operated float, (3) surface detector (plumb-bob), (4) radiation backscatter, (5) radar, (6) HTG, and (7) hybrid gauges. Their ranges go up to 60 m (200 ft). 

It is also possible to employ detectors with solutions flowing over a static mercury drop electrode or a carbon fiber microelectrode, or to use flow-through electrodes, with the electrode simply an open tube or porous matrix. The latter can offer complete electrolysis, namely, coulometric detection. The extremely small dimensions of ultramicroelectrodes (discussed in Section 4.5.4) offer the advantages of flow-rate independence (and hence a low noise level) and operation in nonconductive mobile phases (such as those of normal-phase chromatography or supercritical fluid chromatography). 

The response of the radio frequency discharge detector was reported as 10 mV for a concentration change of 10 g/ml of methyl laureate. The noise level was reported to be 0.05 mV, which would give the minimum detectable concentration for a signal-to-noise ratio of 2 as about 6 x iQ- g/ml. This detector operated at atmospheric pressure and so no vacuum system was required. The effect of temperature on the detector performance was not reported, nor was its linearity over a significant concentration range. This detector was not made available commercially. 

An extract of the sample is separated by reversed phase chromatography. The interfering polymeric matrix is removed by switching columns. A UV detector operating at 235 nm, calibrated with an external standard, is used to determine the level of monomer. 

The antifoam can be added either on a continuous basis or when the foam front reaches a specified level. A series of level detectors is normally present on each drum, as shown in Figure 5. When the foam level is observed at the first level detector, the antifoam injection is started. An immediate drop in the level will be observed. At this time, the operators should be preparing the next drum to begin receiving feed. The antifoam injection will continue for some time after the drum switch occurs as the coke is being quenched with steam and water. 

Breakdown in control and stability of the immediate detector environment with regard to cleanliness, temperature level, power supply, and radiation background interferes with reliable radiation detector operation. Electronic components function best at a cool, constant temperature in a dust-free environment. Special low-temperature and power-supply-stability controls are needed to stabilize the response of gamma-ray spectrometers and liquid scintillation systems. 

These operations must be optimized if the detector is to provide high-quality images at appropriate dose levels. Detectors are characterized by their quantum detection efficiency,sensitivity,spatial resolution properties, noise, dynamic range, and linearity of response. 

Figure 6.24. A laboratory-scale MSMPR crystallizer. A, thermos tat ted feedstock tank B, constant-head tank C, MSMPR crystallizer D, water inlet to jacket E, baffle F, thermometer G, level detector H, solenoid-operated discharge valve /, magma outlet /, control unit...

Ascorbic acid and dehydroascorbic acid levels were determined in plasma. A C column (coulometric detector operated at 100 mV) and an aqueous lOOmM N32HP04 with 2.5 mM EDTA and 2mM -dodecyItrimethylammonium chloride (pH 3) mobile phase were used [1583]. Ascorbic acid eluted in <5 min. Dety-droascorbic acid was determined duough its reduction to ascorbic acid with diththiothreitol. Subtraction of the original ascorbic acid content from the reduced sample content yielded the dehydroascorbic acid result. A 1 ng injection was easily detected. 

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