Filter analogy

Rockland Systems Corp., see under Filters, Analog. 

It is possible to change the conditions in the helium discharge lamp so that the helium is ionized predominantly to He (He II). The radiation is due mainly to the n = 2 — n = transition of He II (analogous to the first member of the Lyman series of the hydrogen atom in Figure 1.1) at 30.4 nm with an energy of 40.81 cY A thin aluminium foil filter can be used to remove any He I radiation. 

Dynamic membranes are concentration—polarization layers formed in situ from the ultrafiltration of coUoidal material analogous to a precoat in conventional filter operations. Hydrous zirconia has been thoroughly investigated other materials include bentonite, poly(acryhc acid), and films deposited from the materials to be separated (18). 

On the analog side, tbe filter is often the conventional resistor-capacitor or RC filter. However, other possibihties exist. For example, one type of A/D converter is called an integrating A/D because the converter basically integrates the input signal over a fixed intei val of time. By making the intei val I/60th second, this approach provides excellent rejection of any 60-Hz electrical noise. 

The resolution of the analog I/O channels of the controller vaiy somewhat, with 12-bit and 14-bit conversions quite common. Sample rates for the majority of the constant sample rate controllers range from I to 10 samples/second. Hard-wired single-pole, low-pass filters are installed on the analog inputs to the controller to protect the sampler from aliasing errors. 

Sample times for the microprocessor-based SLCs vaiy from O.I to 0.4 seconds. Low-pass analog electronic filters are installed on the process inputs to stop abasing errors caused by fast changes in the process signal. Input filter time constants are typically in the range From O.I to I s. Microprocessor-based SLCs may be made part of a DCS by using the communication port (RS-488 is common) on the controller or may be operated in a standalone mode independent of the DCS. 

In the filtration of small amounts of fine particles from liquid by means of bulky filter media (such as absorbent cotton or felt) it has been found that the preceding equations based upon the resistance of a cake of solids do not hold, since no cake is formed. For these cases, in which filtration takes place on the surface or within the interstices of a medium, analogous equations have been developed [Hermans and Bredee, J. Soc. Chem. Ind., 55T, 1 (1936)]. These are usefully summarized, for both constant-pressure and constant-rate conditions, by Grace [Am. In.st. Chem. Eng. J., 2, 323 (1956)]. These equations often apply to the clarification of such materials as sugar solutions, viscose and other spinning solutions, and film-casting dopes. 

Alternatively, reactant and product gases can be distributed to and removed from individual cells through internal pipes in a design analogous to that of filter presses, (iare must be exercised to assure an even flow distribution between the entiv and exit cells. The seals in internally manifolded stacks are generally not subject to electrical, thermal, and mechanical stresses, but are more numerous than in externally manifolded stacks. 

Are there any circuits that are particularly noise-sensitive These include analog-to-digital and digital-to-analog converters, video monitors, etc. This may dictate that the supply has additional filtering or may need to be synchronized to the sensitive circuit. 

Its operation ean be seen as analogous to a meehanieal flywheel and a one-piston engine. The L-C Alter, like the flywheel, stores energy between the power pulses of the driver. The input to the L-C Alter choke input filter) is the ehopped input voltage. The L-C Alter volt-time averages this duty-cyele modulated input voltage waveform. The L-C Altering funetion ean be approximated by... 

By a procedure analogous to that described in the preceding experiment, octalone-2 (12 g, 0.08 mole, Chapter 9, Section III) in ether is added to methylmagnesium iodide in the presence of cuprous bromide (0.2 g). After decomposition with ice-acetic acid, extraction with ether, and washing of the ether extract, the ethereal solution is shaken with an equal volume (50-60 ml) of saturated aqueous sodium bisulfite for 3 hours. The mixture is filtered and the filtrate is reserved. The crystals are washed with ether. The filtrate is separated and the aqueous phase is combined with the filtered solid. The combination is acidified (dilute hydrochloric acid) and heated under reflux for 30 minutes. The product thus liberated is extracted into ether, the ether is washed with bicarbonate, then with saturated aqueous sodium chloride solution, and then dried and evaporated. The residual oil is the desired product, bp 250-254°. 

Piping and filter systems designed by acoustical principles, using a simulation technique on an analog computer. 

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