Electronic regulators

Consider now a situation where, instead of a measuring instrument, one inserts (Fig. 6.31) into the circuit a source of potential (e.g., an electronically regulated power supply). Here, the total potential difference across the cell must equal (in magnitude) that put out by the source.18 This is, in fact, the law of conservation of energy applied to an electrical circuit, or Kirchhoff s second law The algebraic sum of all potential differences around a closed circuit must be equal to zero. For the simple hypothetical system shown in Fig.6.32, one has... 

Figure 11.12—Schematic ant optica path of a single beam spectrophotometer equipped with electronic regulation (Hitachi U-1000). Measurements in solution are often carried out at a fixed wavelength after a calibration curve has been plotted. The use of higher performance double beam UV/Visible spectrometers is not necessary for these measurements in which the spectrum is not recorded. On the other hand, quantitative measurements from mixtures represent a different type of analysis.

In the context of Part 11, one of the differences between Parts 211 and Part 820 is the scope of the electronic records that must be maintained. Part 21 requires the maintenance of electronic regulated data including raw data. Part 820 requires that the results of acceptance activities are recorded, but not necessarily all of the raw regulated data. The exception in 820 is that raw data is required during failure investigations. As in Part 211, results under Part 820 must have audit trails. Refer to Part 820 preamble, pp. 52631 and 52646. 

The basic experimental equipment for FFF is, except for the channel and its support, in general identical to the equipment used for liquid chromatography. It is usually composed of a solvent reservoir, a pump, and an injection system the chromatographic column is replaced by the FFF channel, followed by a detector. The FFF channel can require additional supporting devices, such as a centrifuge for sedimentation FFF or a power supply, and other electronic regulation devices for electrical FFF. If necessary, this basic equipment is complemented by a flow meter at the end of the separation system. For special semipreparative purposes, a fraction collector can be attached to the system. 

Fig. 22. Schematic diagram of a liquid thermostat. N2P, nitrogen under pressure, 3 bars ev, electrovalves N2 liq., liquid nitrogen, T, electronic regulation system Rj heating resistance P, circulating pump hec, heat-exchange coil Th, thermometer A, methanol-water mixture. Adapted from Balny et al. (1975). Reprinted with permission of Analytical Biochemistry. Copyright by Academic Press.

Electronically regulated injection valve for power control... 

Alternatively the tip can be scanned in a constant tunneling current mode. In this case the actually measured current is fed into an electronic regulation circuit which adjusts the actual tip-surface distance to a value resulting in a constant value of the tunneling current at all probed places. The signal fed into the z-axis piezodrive provides information about the local elevation. This mode works... 

The experimental psd relative to the solvent and to PEO solutions (50 and 100 ppm) are shown in Fig. 6 as an example for o, = 1000 rpm. The solvent curve (dashed line) provides the background noise which is only determined by parasitic secondary flows due to the finite volume of the cell and also by the electronic regulation. 

Mechanism Electronic regulation Reversible Permanent inactivation of the overcharged cells by gassing and coating of insidator coating. Irreversible. Active and reversible... 

A variety of AC and DC drives are available for extruders. DC motors with solid-state eontrollers and power supplies provide the most flexible seenario for control. A speed control feedback loop on the drive will minimize variation in the extruder output. The unwind roll should be equipped with a tension control device such as an electronic regulator. 

Eliminating the thermal gradients between the block and the jacket using electronic regulation, which, however, requires sophisticated circuits, can attain the lowest heat transfer and a more complex setup. For this reason, the... 

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